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Mappings

ICD-10-CM

ICD10CM:M12.1 Kaschin-Beck disease

Curator-asserted, not inherited: MONDO records no ICD-10-CM cross-reference for MONDO:0005610 (its coding xrefs are ICD9:716.00/716.06/716.08 and the ICD-11 Foundation term above). `ICD10CM:M12.1` names this disease under the older "Kaschin-Beck" transliteration, which is why the `label` here does not match the entry name character for character - it is ICD-10-CM's canonical label and is copied exactly.

ICD-11 Foundation

icd11f:211396970 Kashin-Beck disease

MONDO asserts `icd11f:211396970` as a `skos:exactMatch` of MONDO:0005610, and the two carry the same label.

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Mechanistic Hypotheses

5

Compound etiology - no single sufficient cause

compound_etiology CANONICAL

Evidence balance 5 support

The position that the disease requires a combination - most often low selenium plus mycotoxin exposure plus a nutritionally marginal diet - and that no single factor is sufficient. Curated as the CANONICAL reading because it is the one the reproducible animal models and the multivariate epidemiology both land on, and because the four single-factor hypotheses below are best understood as its components rather than as its rivals. Its weakness is the obvious one: it fits everything and predicts least.

Pathograph links

Chronic Dietary Selenium Deficiency -> Selenoenzyme Antioxidant Capacity Deficit DIRECT

Dietary T-2 Toxin Exposure -> Chondrocyte Oxidative Stress DIRECT

Show evidence (5 references)

PMID:35304334 SUPPORT Other

"Gradually, four etiological hypotheses have been formed, including water of organic poisoning hypothesis represented by fulvic acid (FA), biogeochemical hypothesis represented by selenium (Se) deficiency, food mycotoxin poisoning hypothesis represented by T-2 toxin poisoning and compound..."

Names the compound hypothesis as a standing position in its own right.

PMID:11482536 SUPPORT Other

"This is an indication that a comprehensive and unifying theory is most likely to be multifactorial."

The review's own conclusion after scoring every competing theory against a standard set of causality criteria.

PMID:11482536 SUPPORT Other

"Although none of the competing theories prevails when they are compared using a predefined and standard set of causality criteria (temporality, strength of the association, biological gradient, experimental evidence, biological plausibility, coherence, specificity and analogy), none should be discounted."

Why the single-factor hypotheses below are curated as ALTERNATIVE rather than retired: none prevails, and none is discountable.

+ 2 more references

Biogeochemical selenium deficiency

selenium_deficiency ALTERNATIVE

Evidence balance 2 support 1 refute

Endemic areas sit on selenium-poor soils, and low selenium starves the selenoenzymes - glutathione peroxidases, thioredoxin reductases, selenoprotein S - that defend chondrocytes against oxidative injury. Curated ALTERNATIVE rather than CANONICAL because it is a component of the compound reading above, not a competitor to it. Its own weaknesses are specific: soil selenium is as low in non-endemic villages as in endemic ones, and a randomised trial in Tibet found selenium had no effect on established disease once iodine deficiency was corrected.

Pathograph links

Chronic Dietary Selenium Deficiency -> Selenoenzyme Antioxidant Capacity Deficit DIRECT

Chronic Dietary Selenium Deficiency -> Selenoprotein S Loss and Wnt Derepression DIRECT

Selenoenzyme Antioxidant Capacity Deficit -> Chondrocyte Oxidative Stress DIRECT

Selenoprotein S Loss and Wnt Derepression -> Endochondral Ossification Failure at the Growth Plate DIRECT

Show evidence (3 references)

PMID:35304334 SUPPORT Other

"Gradually, four etiological hypotheses have been formed, including water of organic poisoning hypothesis represented by fulvic acid (FA), biogeochemical hypothesis represented by selenium (Se) deficiency, food mycotoxin poisoning hypothesis represented by T-2 toxin poisoning and compound..."

Names this hypothesis and the three it competes with.

PMID:42275919 SUPPORT Model Organism

"SelS deficiency activates Wnt/β-catenin, impairing terminal differentiation and contributing to selenium-deficiency cartilage injury."

A specific selenoprotein loss producing a specific cartilage lesion, which is what turns "low selenium" from a correlation into a mechanism.

PMID:12816783 REFUTE Human Clinical

"However, selenium supplementation had no effect on established Kashin-Beck disease, growth, or thyroid function once iodine deficiency was corrected."

Graded REFUTE against the strong form of this hypothesis: in a randomised trial in Tibetan children, selenium did nothing for established disease, growth or thyroid function once iodine was replaced. It does not refute a preventive role, which the same paper is explicit about.

Food mycotoxin poisoning by Fusarium T-2 toxin

t2_mycotoxin ALTERNATIVE

Evidence balance 2 support

T-2 toxin, a trichothecene produced by Fusarium species growing on grain stored damp, is directly chondrotoxic. It is the arm with the most tractable experimental model and the most effective intervention - grain replacement. Curated ALTERNATIVE for the same reason as the selenium arm: the workhorse rat model needs a selenium-deficient or low-nutrition diet alongside the toxin, which is the compound reading rather than this one.

Pathograph links

Dietary T-2 Toxin Exposure -> Chondrocyte Oxidative Stress DIRECT

Dietary T-2 Toxin Exposure -> Ferroptotic Chondrocyte Death DIRECT The toxin reaches ferroptosis without going through the selenium arm, which is why the two hypotheses can each stand alone and also combine.

Chondrocyte Oxidative Stress -> Ferroptotic Chondrocyte Death DIRECT

Show evidence (2 references)

PMID:35304334 SUPPORT Other

"Gradually, four etiological hypotheses have been formed, including water of organic poisoning hypothesis represented by fulvic acid (FA), biogeochemical hypothesis represented by selenium (Se) deficiency, food mycotoxin poisoning hypothesis represented by T-2 toxin poisoning and compound..."

Names this hypothesis alongside the others.

PMID:42103195 SUPPORT Model Organism

"T-2 toxin exposure induced severe articular cartilage degradation, accompanied by intracellular iron overload lipid peroxidation, oxidative stress and distinctive mitochondrial damage characteristic of ferroptosis."

Direct chondrotoxicity of the toxin in a controlled animal experiment in which T-2 toxin was given without a selenium-deficient arm.

Iodine deficiency and hypothyroidism

iodine_deficiency ALTERNATIVE

Evidence balance 3 support

The Tibetan arm of the etiology, and the one this entry previously omitted. Endemic areas around Lhasa are iodine-deficient as well as selenium-poor, and low urinary iodine - not low serum selenium - is the exposure that survived multivariate adjustment in the Tibetan survey. Correcting iodine, not selenium, was what let growth-retarded children recover height. Curated ALTERNATIVE: the epidemiological association is strong and replicated in an intervention, but no cartilage-level mechanism linking thyroid status to the growth-plate lesion is curated here.

Pathograph links

Iodine Deficiency and Hypothyroidism -> Symmetric Growth Arrest and Joint Deformity INDIRECT UNKNOWN INTERMEDIATES Recorded INDIRECT_UNKNOWN_INTERMEDIATES on purpose. Thyroid hormone is required for growth-plate maturation, but this entry curates no cartilage -level evidence connecting the two in this disease; what it has is an epidemiological association and a growth response to iodine replacement.

Show evidence (3 references)

PMID:9770558 SUPPORT Human Clinical

"In areas where severe selenium deficiency is endemic, iodine deficiency is a risk factor for Kashin-Beck disease."

The study's own conclusion, and the clearest statement of this hypothesis.

PMID:9770558 SUPPORT Human Clinical

"When age and sex were controlled for in a multivariate analysis, low urinary iodine, high serum thyrotropin, and low serum thyroxine-binding globulin values were associated with an increased risk of Kashin-Beck disease, but a low serum selenium concentration was not."

The multivariate result that separates the two deficiencies: iodine and thyroid markers survived adjustment and serum selenium did not.

PMID:11482536 SUPPORT Other

"Four factors have been convincingly associated with the disease: selenium deficiency, iodine deficiency, grain contamination with mycotoxin-producing fungi, and water pollution with organic material and fulvic acid."

The causality review's list of the four convincingly associated factors, which includes iodine deficiency alongside the three this entry already curated.

Organic drinking-water poisoning by fulvic acid

fulvic_acid_water ALTERNATIVE

Evidence balance 3 support

Humic and fulvic acids in shallow well water are proposed to generate free radicals that damage cartilage. The mechanistic work is old but real: fulvic acid enhances lipid peroxidation in cartilage cell culture, accumulates in bone and cartilage, and its toxicity falls when its hydroxy group is blocked. The intervention data keep it alive too - improving the water supply measurably reduces incidence, which a purely food-borne model does not predict.

Pathograph links

Fulvic Acid Free-Radical Generation in Cartilage -> Chondrocyte Oxidative Stress DIRECT

Show evidence (3 references)

PMID:35304334 SUPPORT Other

"Gradually, four etiological hypotheses have been formed, including water of organic poisoning hypothesis represented by fulvic acid (FA), biogeochemical hypothesis represented by selenium (Se) deficiency, food mycotoxin poisoning hypothesis represented by T-2 toxin poisoning and compound..."

Names the water organic-poisoning hypothesis and its representative agent.

PMID:10090708 SUPPORT Other

"We hypothesized that FA in drinking water is an etiological factor of Kashin-Beck disease and that the mechanism of action involves the oxy and hydroxy groups in FA for the generation of free radicals."

The hypothesis as its authors stated it, with the chemistry they proposed for it.

PMID:31490368 SUPPORT INDIRECT Human Clinical

"The pooled odds ratios (ORs) and confidence intervals (95% CIs) for primary prevention new incidence in healthy children following interventions to comprehensive measures, change of grain, salt-rich selenium, and improvements of water were 0.15 (0.02, 0.95), 0.15 (0.03, 0.70), 0.19 (0.09, 0.38),..."

Graded INDIRECT: water improvement reducing incidence is consistent with a waterborne agent but does not identify one, since changing the water supply changes more than its fulvic acid content.

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Discussions and Knowledge Gaps

3

Which environmental factor - selenium deficiency, iodine deficiency, T-2 toxin, a water constituent, or an obligate combination - actually causes Kashin-Beck disease?

CONTROVERSY kbd_etiology_unresolved

Attached to

pathophysiology#Chronic Dietary Selenium Deficiency pathophysiology#Dietary T-2 Toxin Exposure pathophysiology#Iodine Deficiency and Hypothyroidism pathophysiology#Fulvic Acid Free-Radical Generation in Cartilage mechanistic_hypotheses#compound_etiology

Seventy years of work has produced four standing single-factor hypotheses and no resolution, which is why this entry curates all of them alongside the compound reading rather than asserting one. Recorded as a CONTROVERSY rather than a knowledge gap: the positions are published and in live disagreement, not merely absent. Each has real support and a real problem. Selenium deficiency has the selenoprotein association data and the preventive trials - but soil selenium is as low in non-endemic villages, and a randomised trial found selenium useless for established disease once iodine was replaced. Iodine deficiency survives multivariate adjustment where selenium does not, and its replacement restored growth - but no cartilage-level mechanism connects it to the lesion. T-2 toxin has the best animal model and the most effective intervention - but the model needs a deficient diet alongside it, and the growth-plate lesion it produces is explicitly unlike the human one. Fulvic acid has the water-improvement result and a 1999 free-radical mechanism, and almost nothing since. The gap matters because the disease is being eliminated by measures that address all of them at once, so the natural experiment that would separate them is closing.

Show evidence (2 references)

PMID:11482536 SUPPORT Other

"Although none of the competing theories prevails when they are compared using a predefined and standard set of causality criteria (temporality, strength of the association, biological gradient, experimental evidence, biological plausibility, coherence, specificity and analogy), none should be discounted."

The causality review's verdict, which is the state this discussion records.

PMID:11482536 SUPPORT Other

"Well-conducted randomised intervention should be the priority of researchers as well as public health professionals to demonstrate what works and what does not."

And its recommendation, which is why the entry curates the preventive trial evidence in as much detail as the mechanistic evidence.

Is the chondrocyte death in Kashin-Beck disease apoptosis, necrosis, necroptosis, or ferroptosis?

INTERPRETATION kbd_death_mode

Attached to

pathophysiology#Mixed-Mode Chondrocyte Death in Deep and Middle Cartilage Zones pathophysiology#Ferroptotic Chondrocyte Death pathophysiology#Chondrocyte Mitochondrial Dysfunction pathophysiology#Smad2 and Smad3 Depletion

The answer appears to be "several, sorted by cartilage zone", which is unusual enough to be worth stating rather than smoothing. Caspase-3 is not raised in patient cartilage, so classic apoptosis is not the main event; RIP3 positivity puts necroptosis in the middle zone; ultrastructure shows frank necrosis in the deep zone; mitochondrial dysfunction with cytochrome c release and caspase-9 activation is measurable in cultured patient chondrocytes; and the ferroptosis work adds a further mode driven specifically by the toxin. The Smad2/Smad3 result supplies a mechanism for the split - the two proteins are lost together under oxidative stress and each loss produces a different death. This entry therefore curates one node for mixed-mode death plus separate ferroptosis and mitochondrial nodes, rather than choosing a mode.

Is the epiphyseal plate in Kashin-Beck disease under-vascularised or over-vascularised?

INTERPRETATION kbd_vascular_direction

Attached to

pathophysiology#Type H Vessel Proliferation at the Epiphyseal Plate pathophysiology#Endochondral Ossification Failure at the Growth Plate

Two curated observations point opposite ways, and this entry records both rather than choosing. The 2001 histology of phalanges from affected children found the proximal cartilage end plate unvascularised, and proposed that the disease develops from a failure of metaphyseal angiogenesis. The 2026 type H vessel work found the opposite in the rat - vessels proliferating at the epiphyseal plate, delivering more toxin, with the loop demonstrated pharmacologically in both directions. They are not necessarily in conflict: different species, different bones, different stages, and "vascularisation of the cartilage end plate" and "type H vessel density at the plate" are not the same measurement. But nothing curated here reconciles them, and the pathograph currently carries only the proliferative reading as an edge.

Show evidence (2 references)

PMID:11482529 SUPPORT Human Clinical

"These observations suggest that Kashin-Beck disease could develop from an alteration of the angiogenesis of the metaphyseal cartilage resulting in degeneration with consequent joint dysplasia, which may be associated with a decrease in growth of the diaphyseal bones."

The angiogenesis-failure reading, from human phalangeal histology.

PMID:42000119 REFUTE Model Organism

"Conversely, HF reduced type H vessel proliferation (MD: -3.70, 95%CI: -6.67, -0.73), decreased T-2 toxin levels and suppressed inflammation (MD: -0.17, 95%CI: -0.23, -0.11), while preserving proteoglycan content and cartilage morphology."

Graded REFUTE against the angiogenesis-failure reading: suppressing vessel proliferation protected the cartilage, which is the opposite of what a model of insufficient vascularisation predicts.

⚙

Pathophysiology

16

Chronic Dietary Selenium Deficiency

A child in an endemic area eats grain grown on selenium-poor soil, and circulating and cartilage selenium stay low through the years the growth plates are open. Curated as its own node rather than bundled with the toxin exposure, because the two have different exposure routes, different interventions, and different edges out of this graph.

Biogeochemical selenium deficiency Compound etiology - no single sufficient cause

Downstream

Selenoenzyme Antioxidant Capacity Deficit

Selenoprotein S Loss and Wnt Derepression

Show evidence (2 references)

PMID:31548049 SUPPORT Human Clinical

"Multivariate regression analysis suggested that etiology of the KBD was food-related factors such as fungal contamination of grains, selenium deficiency, imbalance of protein intake, etc."

The multivariate epidemiological result naming selenium deficiency among the food-related factors.

PMID:41272335 SUPPORT Human Clinical

"The results showed that the average soil selenium content in both endemic and non-endemic villages across the six provinces was below 0.2 mg/kg."

Curated because it complicates the exposure rather than confirming it: soil selenium was low in endemic and non-endemic villages alike.

Dietary T-2 Toxin Exposure

The other half of the initiating state: T-2 toxin from Fusarium growing on damp-stored grain, ingested over years. Separated from the selenium node because the experimental evidence separates them - T-2 toxin alone degrades articular cartilage in the rat, and the deep-zone lesion that actually resembles the human disease is the one that needs both.

Compound etiology - no single sufficient cause Food mycotoxin poisoning by Fusarium T-2 toxin

Animal models

Rhesus monkey fed endemic water and grain Rhesus monkey recapitulates Reproduces the disease using the endemic exposure itself rather than a reconstructed one.

Downstream

Chondrocyte Oxidative Stress

Ferroptotic Chondrocyte Death The toxin reaches ferroptosis without going through the selenium arm, which is why the two hypotheses can each stand alone and also combine.

Show evidence (2 references)

PMID:35304334 SUPPORT Other

"The main etiological mechanism for Kashin-Beck disease (KBD) is deep chondrocyte necrosis induced by environmental risk factors (ERFs)."

States the field's summary of what initiates the disease - environmental risk factors producing deep chondrocyte necrosis.

PMID:42103195 SUPPORT Model Organism

"T-2 toxin exposure induced severe articular cartilage degradation, accompanied by intracellular iron overload lipid peroxidation, oxidative stress and distinctive mitochondrial damage characteristic of ferroptosis."

The toxin alone degrading articular cartilage in a controlled experiment.

Iodine Deficiency and Hypothyroidism

In the Tibetan endemic area iodine deficiency is severe enough to produce goitre in nearly half of children and biochemical hypothyroidism in a quarter of those with the disease, and it is the exposure that survives multivariate adjustment where serum selenium does not. Curated as an initiating node because the interventional evidence points the same way - growth-retarded children recovered height when iodine was replaced, whether or not they also received selenium.

Iodine deficiency and hypothyroidism

Downstream

Symmetric Growth Arrest and Joint Deformity Recorded INDIRECT_UNKNOWN_INTERMEDIATES on purpose. Thyroid hormone is required for growth-plate maturation, but this entry curates no cartilage -level evidence connecting the two in this disease; what it has is an epidemiological association and a growth response to iodine replacement.

Show evidence (2 references)

PMID:9770558 SUPPORT Human Clinical

"Among the 575 subjects, 280 (49 percent) had Kashin-Beck disease, 267 (46 percent) had goiter"

The co-occurrence of the disease and goitre in the same survey population.

PMID:9770558 SUPPORT Human Clinical

"When age and sex were controlled for in a multivariate analysis, low urinary iodine, high serum thyrotropin, and low serum thyroxine-binding globulin values were associated with an increased risk of Kashin-Beck disease, but a low serum selenium concentration was not."

The result this node rests on - low urinary iodine associated with the disease after adjustment, low serum selenium not.

Fulvic Acid Free-Radical Generation in Cartilage

The mechanism proposed for the water-organic-poisoning hypothesis: oxy and hydroxy groups on fulvic acid interact with the chondrocyte membrane and drive lipid peroxidation, and fulvic acid concentrates in the two tissues selenium does not reach. Curated as a node so the ALTERNATIVE hypothesis tags a real edge rather than standing outside the graph, and because the water-improvement intervention now has somewhere to point.

Organic drinking-water poisoning by fulvic acid

Downstream

Chondrocyte Oxidative Stress

Show evidence (2 references)

PMID:10090708 SUPPORT In Vitro

"Cartilage cell culture experiments indicated that the oxy or hydroxy functional groups in FA may interfere with the cell membrane and result in enhancement of lipid peroxidation."

The cartilage cell-culture result behind the free-radical mechanism.

PMID:10090708 SUPPORT Model Organism

"FA accumulated in bone and cartilage, where selenium rarely concentrates."

The tissue distribution that makes the proposal specific to this disease - fulvic acid reaches bone and cartilage, where selenium does not.

Selenoenzyme Antioxidant Capacity Deficit

Without selenium the selenoproteins cannot be made, and chondrocytes lose the antioxidant capacity they rely on. Measured directly in the rat model as reduced total antioxidant capacity, catalase, superoxide dismutase and glutathione peroxidase in serum and cartilage, at both activity and mRNA level, and in patient cartilage as loss of GPx6 from the deep zone.

Biogeochemical selenium deficiency

GPX6 hgnc:4558

cellular oxidant detoxification GO:0098869 ↓ DECREASED

glutathione peroxidase activity GO:0004602 ↓ DECREASED

Animal models

T-2 toxin plus selenium-deficient diet rat Rat recapitulates The model reproduces the biochemical deficit directly: antioxidant enzyme activity and mRNA down, lipid peroxidation up, in both serum and cartilage.

Downstream

Chondrocyte Oxidative Stress

Show evidence (3 references)

PMID:22294316 SUPPORT Model Organism

"The levels of thiobarbituric acid reactive substances (TBARS), indicative of lipid peroxidation in serum and cartilage, were significantly increased in all experimental groups compared to the normal diet group, while the levels of antioxidants, measured as total antioxidant capacity (T-AOC),..."

The measurement this node is named for - antioxidant capacity down and lipid peroxidation up in serum and cartilage of the model.

PMID:22294316 SUPPORT Model Organism

"The mRNA expression of those antioxidants in cartilage tissue was significantly reduced by T-2 toxin alone or by selenium-deficient diet plus T-2 toxin treatment."

The loss is transcriptional as well as functional, and the toxin alone is enough to produce it.

PMID:42384133 SUPPORT Human Clinical

"In articular cartilage from children with KBD, GPx6 expression was markedly reduced"

The same deficit in patient cartilage, and zone-matched to where the chondrocytes die.

Selenoprotein S Loss and Wnt Derepression

Selenoprotein S loss de-represses Wnt/beta-catenin signalling and derails terminal chondrocyte differentiation. Curated as its own node rather than folded into the antioxidant deficit above, because it is a different lesion with a different route out of the graph: it reaches the growth plate through failed differentiation rather than through oxidant damage.

Biogeochemical selenium deficiency

SELENOS hgnc:30396

canonical Wnt signaling pathway GO:0060070 ↑ INCREASED terminal chondrocyte differentiation GO:0002062 ↓ DECREASED

Downstream

Endochondral Ossification Failure at the Growth Plate

Show evidence (1 reference)

PMID:42275919 SUPPORT Model Organism

"SelS deficiency activates Wnt/β-catenin, impairing terminal differentiation and contributing to selenium-deficiency cartilage injury."

Establishes the selenoprotein-to-cartilage link with a knockout, and names the specific pathway it runs through.

Chondrocyte Oxidative Stress

The convergence point of every arm of the etiology. Oxidant load rises in chondrocytes because their selenoenzyme defences are depleted, because the toxin generates radicals, because fulvic acid drives membrane lipid peroxidation, or in some combination.

Food mycotoxin poisoning by Fusarium T-2 toxin

chondrocyte CL:0000138

response to oxidative stress GO:0006979 ↑ INCREASED

Downstream

Smad2 and Smad3 Depletion

Chondrocyte Mitochondrial Dysfunction

Ferroptotic Chondrocyte Death

Show evidence (3 references)

PMID:33769459 SUPPORT Other

"The occurrence and development of an endemic OA, Kashin-Beck disease (KBD), is closely related to oxidative stress induced by free radicals."

The framing the paper opens with. Graded OTHER: it states the field's position rather than the study's own measurement.

PMID:33769459 SUPPORT Other

"These studies reveal that oxidative stress causes necrosis of hypertrophic chondrocytes by downregulating Smad2 protein, which increases the pathogenesis of KBD cartilage."

The paper's conclusion, which is the edge from this node to the next one. Graded OTHER because the conclusion rests on in vitro and in vivo results together and no single evidence source describes it.

PMID:22294316 SUPPORT Model Organism

"The levels of thiobarbituric acid reactive substances (TBARS), indicative of lipid peroxidation in serum and cartilage, were significantly increased in all experimental groups compared to the normal diet group, while the levels of antioxidants, measured as total antioxidant capacity (T-AOC),..."

The oxidant load measured directly in cartilage of the compound rat model.

Chondrocyte Mitochondrial Dysfunction

Respiratory chain complexes II to V run at reduced activity in chondrocytes taken from adult patients, ATP falls, membrane potential collapses and cytochrome c is released with caspase-9 and caspase-3 activation. This is the intrinsic apoptotic route into the mixed cell death below, and the one measured in human cells rather than inferred from a model.

chondrocyte CL:0000138

mitochondrial electron transport chain activity GO:0022900 ↓ DECREASED

Downstream

Mixed-Mode Chondrocyte Death in Deep and Middle Cartilage Zones

Show evidence (4 references)

PMID:20650322 SUPPORT In Vitro

"Activities of complexes II, III, IV and V were reduced in KBD articular chondrocytes compared with cells from normal controls."

The respiratory-chain measurement this node records, in chondrocytes cultured from patients.

PMID:20650322 SUPPORT In Vitro

"Cultured KBD chondrocytes had a reduction of cellular ATP levels and contained a higher proportion of cells with de-energized mitochondria."

The functional consequence - less ATP, and more de-energized mitochondria.

PMID:20650322 SUPPORT In Vitro

"Mitochondrial cytochrome c release and activation of caspase-9 and 3 were also observed."

The intrinsic apoptotic route out of this node, which is the edge to the mixed-mode death below.

+ 1 more reference

Smad2 and Smad3 Depletion

Oxidative stress strips Smad2 and Smad3 from hypertrophic chondrocytes, and the two losses produce different deaths - Smad2 loss necrosis, Smad3 loss apoptosis. This is the cleanest molecular account of why the cell death in this disease is mixed rather than of one type.

hypertrophic chondrocyte CL:0000743

Downstream

Mixed-Mode Chondrocyte Death in Deep and Middle Cartilage Zones

Show evidence (2 references)

PMID:33769459 SUPPORT In Vitro

"Reduction of Smad2 protein induced necrotic death of hypertrophic chondrocytes, while reduction of Smad3 protein induced apoptosis."

The dissociation this node records: two related proteins, two different modes of death.

PMID:33769459 SUPPORT Human Clinical

"In the cartilage of KBD patients, the expression of Smad2 and Smad3 proteins in the middle and deep zone was significantly decreased with an observed full deletion in the deep zone of some samples."

The same depletion in patient cartilage, zone by zone, which is what makes the in vitro result relevant to the human disease.

Ferroptotic Chondrocyte Death

T-2 toxin drives iron overload and lipid peroxidation in articular chondrocytes by suppressing the Nrf2/xCT/GPX4 axis, and loss of GPx6 sits upstream of the same axis in patient cartilage. Curated as its own node because it is pharmacologically separable: an iron chelator reverses it.

ferroptosis GO:0097707 ↑ INCREASED

Downstream

Mixed-Mode Chondrocyte Death in Deep and Middle Cartilage Zones

Show evidence (3 references)

PMID:42103195 SUPPORT Model Organism

"Our findings demonstrate that T-2 toxin induces ferroptosis in articular chondrocytes, at least partially, through the suppression of the Nrf2/xCT/GPX4 axis."

The mechanism and the axis it runs through.

PMID:42103195 SUPPORT Model Organism

"T-2 toxin exposure induced severe articular cartilage degradation, accompanied by intracellular iron overload lipid peroxidation, oxidative stress and distinctive mitochondrial damage characteristic of ferroptosis."

The phenotype, including the mitochondrial morphology that identifies ferroptosis.

PMID:42384133 SUPPORT Model Organism

"Gpx6 knockout mice exhibited signs of ECM degradation in articular cartilage, along with an enhanced susceptibility to T-2 toxin exposure."

A knockout of the selenoenzyme that sits upstream of the axis reproduces matrix degradation and sensitises the animal to the toxin, which links the selenium arm to this toxin-driven node.

Mixed-Mode Chondrocyte Death in Deep and Middle Cartilage Zones

Chondrocytes die by several mechanisms at once and the mechanisms sort by cartilage zone: necroptosis dominates the middle zone in children, frank necrosis the deep zone. Caspase-3 is not raised, so classic apoptosis is not the whole story. This entry does not force a single mode.

chondrocyte CL:0000138

necroptotic process GO:0070266 ↑ INCREASED apoptotic process GO:0006915 ↑ INCREASED

Animal models

T-2 toxin plus selenium-deficient diet rat Rat recapitulates Apoptosis and necroptosis co-exist in the middle zone of the model's cartilage, as they do in children with the disease, and the deep-zone chondronecrosis is described as very similar to the human lesion.

Downstream

Endochondral Ossification Failure at the Growth Plate

Articular Cartilage Matrix Degradation

Type H Vessel Proliferation at the Epiphyseal Plate The inflammation accompanying chondrocyte injury upregulates IL-6 and SELE, which drives the vascular response.

Show evidence (3 references)

PMID:30680829 SUPPORT Human Clinical

"Immunohistochemistry failed to detect significant differences in caspase-3 levels in KBD children compared to controls, suggesting that beside apoptosis necroptosis dominates as a cell death mechanism in the middle zone of cartilage from KBD children."

The negative caspase-3 result and the RIP3 positivity together, which is what makes this node "mixed-mode" rather than apoptotic.

PMID:30680829 SUPPORT Human Clinical

"Ultrastructural analysis of chondrocyte from deep cartilage revealed abnormal cells with numerous morphological changes, such as plasma membrane breakdown, generalized swelling of the cytoplasm and loss of identifiable organelles."

The ultrastructural necrosis in the deep zone, distinct from the middle-zone picture. The cached full text places this analysis in the children's cartilage (Figure 5), not in the rat arm the abstract describes immediately before it.

PMID:30680829 SUPPORT Other

"Chondrocyte death plays a key role in either the initiation or the progression of KBD pathogenesis."

Places this node at the centre of the disease rather than downstream of it. Graded OTHER: the sentence is the paper's closing interpretation rather than one of its measurements.

Type H Vessel Proliferation at the Epiphyseal Plate

Type H vessels multiply in the growing epiphyseal plate and carry more T-2 toxin to it, so the vascular response feeds the injury that provoked it. The loop is demonstrated in both directions pharmacologically, which is unusually strong for a feedback claim.

epiphyseal plate UBERON:0002516

Downstream

Mixed-Mode Chondrocyte Death in Deep and Middle Cartilage Zones The amplifying limb: more vessels, more toxin delivered to the plate, more chondrocyte death.

Show evidence (2 references)

PMID:42000119 SUPPORT Model Organism

"Conversely, HF reduced type H vessel proliferation (MD: -3.70, 95%CI: -6.67, -0.73), decreased T-2 toxin levels and suppressed inflammation (MD: -0.17, 95%CI: -0.23, -0.11), while preserving proteoglycan content and cartilage morphology."

The mirror-image experiment: inhibiting the vessels reduced toxin, inflammation and cartilage damage. Two-directional pharmacology is what makes this node causal rather than associated.

PMID:42000119 SUPPORT Model Organism

"Single-cell RNA sequencing, qPCR and explants revealed that T-2 toxin-induced inflammation upregulated IL-6 and SELE, promoting type H vessels proliferation."

The signalling route from chondrocyte injury to the vascular response.

Articular Cartilage Matrix Degradation

Alongside the growth-plate lesion, the articular matrix itself is degraded: matrix metalloproteinases rise, type II collagen and proteoglycan fall. TSG-6 is over-expressed through all three cartilage zones in patients and, when silenced, takes the metalloproteinases down with it - so it is a driver of the degradation rather than a marker of it.

TSG-6 hgnc:11898

extracellular matrix disassembly GO:0022617 ↑ INCREASED

articular cartilage UBERON:0010996

Downstream

Secondary Degenerative Arthropathy

Show evidence (4 references)

PMID:36468025 SUPPORT Human Clinical

"TSG-6 was upregulated in KBD chondrocytes at the mRNA level and upregulated in the superficial, middle, and deep zones of KBD cartilage."

The expression finding in patient cartilage, zone by zone.

PMID:36468025 SUPPORT In Vitro

"Compared with the blank control group, the expression of MMPs was increased in the intervention group of HT-2 toxin, while the expression of proteoglycan and COL2A1 decreased (p < 0.05)."

The toxin metabolite reproducing the matrix picture in chondrocyte culture - metalloproteinases up, collagen and proteoglycan down.

PMID:36468025 SUPPORT In Vitro

"After TSG-6 silencing, the expression of MMP1, MMP3, MMP13, and proteoglycan was significantly decreased while COL2A1 expression was significantly increased, which was reversed after the overexpression of TSG-6 induced by TNF-α (p < 0.05)."

The silencing and rescue experiment, which is what makes TSG-6 a driver of the degradation here rather than a marker of it.

+ 1 more reference

Endochondral Ossification Failure at the Growth Plate

Where the chondrocytes die, the growth plate cannot convert cartilage to bone, and ossification becomes irregular. The oldest histology of the disease describes the same failure from a different angle: the proximal cartilage end plate of the phalanx is unvascularised, with epiphyseal bone formation altered around it.

ossification GO:0001503 ↓ DECREASED

epiphyseal plate UBERON:0002516

Animal models

T-2 toxin plus selenium-deficient diet rat Rat fails to recapitulate The rat's growth-plate chondronecrosis is explicitly not similar to the human lesion, which is the failure this entry records rather than smooths over. The primary report attributes it to the rat's growth plates never closing.

Low-nutrition diet plus T-2 toxin rat Rat partially recapitulates Blurred, thin and irregular epiphyseal plates with chondrocyte necrosis and shortened tibias, which the authors read as closely matching the human bone changes.

Downstream

Symmetric Growth Arrest and Joint Deformity

Show evidence (3 references)

PMID:42000119 SUPPORT Other

"Kashin-Beck disease (KBD) primarily impairs the epiphyseal plate in children and adolescents, resulting in enlarged bone ends and short stature."

States the target tissue and the growth consequence. Graded OTHER: the sentence is the paper's framing of the disease rather than its own result.

PMID:11482529 SUPPORT Human Clinical

"The prevailing characteristic of the samples is the absence of vascularisation within the proximal cartilage end plate of the phalanx associated with an alteration of the epiphyseal bone formation."

The histological finding in patient phalanges - no vascularisation of the cartilage end plate, and altered epiphyseal bone formation with it.

PMID:23701828 SUPPORT Model Organism

"In group D, all epiphyseal plates were blurred, thin, and irregular."

The radiographic plate change in the low-nutrition plus T-2 toxin rat - blurred, thin and irregular plates, with shortened tibias.

Symmetric Growth Arrest and Joint Deformity

Because the growth plates fail while the child is still growing, the shortening is symmetric and affects the most actively growing bones. The clinical result is the triad the disease is recognised by: enlarged finger joints, shortened fingers, and short stature.

Show evidence (2 references)

PMID:31335683 SUPPORT Other

"Kashin-Beck disease (KBD) is known for some typical characters like finger joint enlargement, shortened fingers, and dwarfism."

The clinical triad this node produces. Graded OTHER: the sentence is a case report's framing of the disease rather than a study result.

PMID:23701828 SUPPORT Model Organism

"A rat model of KBD induced by a low-nutrition diet and T-2 toxin exposure demonstrated radiographic and histopathological abnormalities of the proximal epiphyseal plate and the tibial metaphysis that are very similar to the bone changes found in patients with KBD."

The model's own account of the same outcome - plate and metaphyseal changes matching those in patients.

Secondary Degenerative Arthropathy

The articular cartilage damage does not stop when growth does. Adults carry a deforming arthropathy with pain and restricted movement, graded radiographically much as primary osteoarthritis is - which is also why the disease is easy to mistake for it outside endemic areas.

articular cartilage UBERON:0010996

Show evidence (1 reference)

PMID:41342918 SUPPORT Human Clinical

"The X-ray grading of adult KBD ankles was conducted using the Kellgren-Lawrence grading as a reference."

That the adult disease is graded on the standard osteoarthritis scale is the evidence for treating this as a degenerative arthropathy.

✶

Histopathology

3

Deep-Zone Acellular Areas with Surrounding Chondrocyte Clusters

The characteristic cartilage picture: patches in the deep zone emptied of chondrocytes, ringed by clusters of surviving cells, with the remaining cells staining palely. The clustering is the cartilage's attempt to repopulate what the necrosis removed.

Show evidence (1 reference)

PMID:30680829 SUPPORT Human Clinical

"In KBD cartilage chondrocyte death was characterized by paler staining of the cells. Multiple chondral cell clusters surrounded the areas lacking cells in the deep zone."

The finding this record names, in patient cartilage.

Zone-Dependent Cell Death Markers

TUNEL and RIP3 positivity concentrate in the middle zone while frank necrotic ultrastructure sits in the deep zone - the histological basis for this entry treating chondrocyte death as mixed-mode and zone-sorted rather than uniform.

Show evidence (2 references)

PMID:30680829 SUPPORT Human Clinical

"The per cent of TUNEL-positive and RIP3-positive chondrocytes were higher in the middle zones of KBD samples"

The zonal distribution of the death markers.

PMID:30680829 SUPPORT Human Clinical

"Ultrastructural analysis of chondrocyte from deep cartilage revealed abnormal cells with numerous morphological changes, such as plasma membrane breakdown, generalized swelling of the cytoplasm and loss of identifiable organelles."

The deep-zone ultrastructure, which is a different picture from the middle zone. The cached full text places the transmission electron microscopy in cartilage from affected children (Figure 5), not in the rat arm.

Absent Vascularisation of the Phalangeal Cartilage End Plate

In supernumerary fingers removed from affected children and in intra-articular bodies from advanced cases, the proximal cartilage end plate of the phalanx carries no vascularisation, and epiphyseal bone formation around it is altered.

Show evidence (1 reference)

PMID:11482529 SUPPORT Human Clinical

"The prevailing characteristic of the samples is the absence of vascularisation within the proximal cartilage end plate of the phalanx associated with an alteration of the epiphyseal bone formation."

The finding this record names, and the observation behind the angiogenesis-failure reading discussed under `kbd_vascular_direction`.

⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

●

Phenotypes

7

Limbs 1

Brachydactyly HP:0001156

An earlier draft of this record called brachydactyly the earliest sign because the phalangeal growth plates are affected first. Neither half of that is supported by anything cited here, and it has been removed rather than left standing on a plausible-sounding argument.

Show evidence (2 references)

PMID:31335683 SUPPORT Other

"Kashin-Beck disease (KBD) is known for some typical characters like finger joint enlargement, shortened fingers, and dwarfism."

Names shortened fingers among the typical characters of the disease. Graded OTHER: a case report's framing rather than a study result.

PMID:29459762 SUPPORT INDIRECT Human Clinical

"When screening for Kashin-Beck disease (KBD) in children, hand X-ray examination is the most important measure."

Graded INDIRECT: that hand radiography is the primary screening measure is why the digital findings are treated as the index feature, but the sentence does not itself describe shortened fingers.

Musculoskeletal 3

Enlarged Joints HP:0003037

Show evidence (2 references)

PMID:42000119 SUPPORT Other

"Kashin-Beck disease (KBD) primarily impairs the epiphyseal plate in children and adolescents, resulting in enlarged bone ends and short stature."

Names enlarged bone ends as a consequence of the epiphyseal-plate lesion. Graded OTHER as the paper's framing rather than its own measurement.

PMID:31335683 SUPPORT Other

"Kashin-Beck disease (KBD) is known for some typical characters like finger joint enlargement, shortened fingers, and dwarfism."

Names finger joint enlargement among the typical characters of the disease.

Joint Stiffness and Restricted Movement HP:0001387

Show evidence (1 reference)

PMID:12816783 SUPPORT Human Clinical

"The frequencies of joint pain, decreased joint mobility, and radiologic abnormalities were not significantly different between the 3 groups at 12 mo."

Decreased joint mobility is one of the three outcomes the Tibetan supplementation trial measured, which is the evidence that it is a standard manifestation. The sentence also records the trial's negative result on it.

Sarcopenia Risk Skeletal muscle atrophy HP:0003202

Bound to the closest available HP term. `HP:0003202` names muscle atrophy; what was measured is a SARC-F screening score, which is a risk instrument rather than a confirmed diagnosis, and `preferred_term` carries that distinction.

Show evidence (1 reference)

PMID:39770964 SUPPORT Human Clinical

"KBD as an independent risk factor increased the risk of sarcopenia for patients."

The independent association this record names, after propensity-score matching within the endemic area.

Nervous System 1

Depression HP:0000716

Show evidence (2 references)

PMID:40963707 SUPPORT Human Clinical

"Depression was present in 53.2% of patients in our KBD samples."

The measured prevalence on PHQ-9 in a field survey of 440 subjects in endemic areas of northwest China.

PMID:40963707 SUPPORT Human Clinical

"Being male (odds ratio [OR]: 0.296, 95% confidence interval [CI]: 0.180-0.486, p < 0.001) was an independent protective factor for depression, while the presence of comorbid chronic diseases (OR: 4.701, 95% CI: 2.292-9.640, p < 0.001), and a higher visual analog scale (VAS) pain level (OR:..."

The associated factors this record names, from the same logistic regression.

Constitutional 1

Joint Pain Arthralgia HP:0002829

Show evidence (2 references)

PMID:41342918 SUPPORT Human Clinical

"This paper aims to establish an X-ray imaging grading for assessing ankle joints in adult Kashin-Beck disease (KBD) and investigate its correlation with clinical grading of finger and ankle pain."

Establishes pain as the clinical endpoint the radiographic grading is correlated against.

PMID:31376086 SUPPORT Human Clinical

"In adults, chondroitin plus glucosamine was the best for pain (standardised mean difference 1.46, 95% CI 1.07-1.85), followed by intra-articular injection of hyaluronic acid (IAH) (1.09, 0.70-1.48), chondroitin (0.84, 0.47-1.21), diclofenac (0.63, 1.18-1.08), naproxen (0.55, 0.12-0.98),..."

Pain is the primary outcome of the adult treatment literature, which is the strongest evidence that it is the dominant adult manifestation.

Growth 1

Short Stature HP:0004322

Onset: CHILDHOOD; 3-12y

Show evidence (2 references)

PMID:42000119 SUPPORT Other

"Kashin-Beck disease (KBD) primarily impairs the epiphyseal plate in children and adolescents, resulting in enlarged bone ends and short stature."

Names short stature as a direct consequence of the growth-plate lesion. Graded OTHER as the paper's framing rather than its own measurement.

PMID:40963707 SUPPORT Other

"Kashin-Beck disease (KBD) is an endemic osteoarthropathy, which occurs in children aged 3-12, with similarity to osteoarthritis (OA)."

The onset window recorded on this phenotype. Graded OTHER: a background sentence rather than the study's own result.

🧬

Genetic Associations

5

SELENOS susceptibility variant

Gene: SELENOS hgnc:30396 relationship_type: SUSCEPTIBILITY variant_origin: GERMLINE

Show evidence (3 references)

PMID:33844169 SUPPORT Human Clinical

"We conclude that the DIO2 (rs225014), SEPS1 (-105G>A), and Sep15 (rs5859) gene polymorphism are associated with susceptibility to KBD."

The meta-analysis conclusion naming this locus among the three associated ones.

PMID:33844169 SUPPORT Human Clinical

"The OR and 95%CI for SEPS1 (-105G>A) were 2.47 (1.85, 3.29), 9.36 (4.58, 19.12), 2.17 (1.53, 3.08), and 8.60 (4.25, 17.38) in the allele, homozygote, dominant, and recessive models, respectively."

The pooled effect estimates this record's `frequency` reports.

PMID:33844169 SUPPORT Human Clinical

"There were a total of eight included case-control studies covering 2025 KBD patients and 1962 controls."

The size of the pooled sample behind those estimates.

SELENOF susceptibility variant

Gene: SELENOF hgnc:17705 relationship_type: SUSCEPTIBILITY variant_origin: GERMLINE

Show evidence (2 references)

PMID:33844169 SUPPORT Human Clinical

"We conclude that the DIO2 (rs225014), SEPS1 (-105G>A), and Sep15 (rs5859) gene polymorphism are associated with susceptibility to KBD."

The meta-analysis conclusion naming this locus among the three associated ones.

PMID:33844169 SUPPORT Human Clinical

"In addition, the OR and 95%CI for Sep15 (rs5859) were 2.05 (1.06, 3.96) in the allele model."

The pooled estimate, and the one with the widest interval of the three - it only just clears 1.

DIO2 variant

Gene: DIO2 hgnc:2884 relationship_type: PROTECTIVE variant_origin: GERMLINE

Show evidence (4 references)

PMID:33844169 SUPPORT Human Clinical

"We conclude that the DIO2 (rs225014), SEPS1 (-105G>A), and Sep15 (rs5859) gene polymorphism are associated with susceptibility to KBD."

The meta-analysis conclusion naming this locus among the three associated ones. Read with the numbers, not the wording: the sentence says "susceptibility" for all three loci together, while all three of its pooled DIO2 estimates run below 1. This record follows the estimates, which is why it is PROTECTIVE rather than SUSCEPTIBILITY.

PMID:33844169 SUPPORT Human Clinical

"Meta-analysis results show that the pooled odds ratios (OR) and 95% confidence intervals (CI) for DIO2 (rs225014) were 0.69 (0.52, 0.91), 0.69 (0.50, 0.96), and 0.72 (0.52, 0.99) in the allele, heterozygote, and dominant models, respectively."

The pooled estimates, all three below 1, which is what makes this record PROTECTIVE rather than SUSCEPTIBILITY.

PMID:24058403 REFUTE Human Clinical

"In this study, we showed that single SNPs in the genes GPX1 (rs1050450, rs1800668 and rs3811699), TrxR2 (rs5748469), and DIO2 (rs225014) may not be significantly associated with KBD in a Tibetan population."

The replication failure in a Tibetan population, which is why this record says the effect is not established rather than reporting the pooled estimate alone.

+ 1 more reference

ADAM12 susceptibility variants

Gene: ADAM12 hgnc:190 relationship_type: SUSCEPTIBILITY variant_origin: GERMLINE

Show evidence (3 references)

PMID:27545300 SUPPORT Human Clinical

"In the BGWAS, ADAM12 gene achieved the most significant association (rs1278300 p-value = 9.25 × 10(-9)) with the KBD."

The discovery association from a two-stage bivariate genome-wide scan in 2,417 subjects.

PMID:27545300 SUPPORT Human Clinical

"Immunohistochemistry revealed significantly decreased expression level of ADAM12 protein in the KBD articular cartilage (average positive chondrocyte rate = 47.59 ± 7.79%) compared to healthy articular cartilage (average positive chondrocyte rate = 64.73 ± 5.05%)."

The protein-level follow-up in patient cartilage, which is what makes this a mechanistic lead rather than a bare association signal.

PMID:33844169 NO_EVIDENCE Human Clinical

"PubMed, Google Scholar, Cochrane library, and Chinese National Knowledge Infrastructure (CNKI) were electronically searched using the terms "selenoprotein" and "Kashin-Beck disease" or "KBD" with a search time from the establishment of the database to January 2021."

Graded NO_EVIDENCE and curated here on purpose: the selenoprotein meta-analysis searched on the two terms "selenoprotein" and "Kashin-Beck disease", so it bears on this gene not at all and could not have found it. That is the reason the retracted claim about selenoprotein genes versus cartilage genes was never supportable from it.

Selenoprotein loci tested and not associated

Gene: GPX1 hgnc:4553 relationship_type: DISPUTED variant_origin: GERMLINE

Show evidence (2 references)

PMID:33844169 REFUTE Human Clinical

"For GPX1 (rs1050450, rs1800668, rs3811699), DIO2 (rs225014, rs1352815, rs1388382), TrxR2 (rs1139793, rs5746841), GPX4 (rs713041, rs4807542), and SEPP1 (rs7579, 25191g/a), there was no significant statistical difference between the KBD and control groups (P>0.05)."

Graded REFUTE against this record's own claim, which is the claim that these loci confer susceptibility. The meta-analysis tested them and found no difference between cases and controls.

PMID:24058403 REFUTE Human Clinical

"In this study, we showed that single SNPs in the genes GPX1 (rs1050450, rs1800668 and rs3811699), TrxR2 (rs5748469), and DIO2 (rs225014) may not be significantly associated with KBD in a Tibetan population."

The same negative result in an independent Tibetan population.

💊

Medical Actions

10

Grain Replacement

Action: replacement of the contaminated staple grain supply Ontology label: Preventive Intervention NCIT:C15843

Platform: Behavioral / lifestyle

Replacing the locally grown, mycotoxin-contaminated staple grain with grain from outside the endemic area. Tied with comprehensive multi-component programmes as the most effective primary prevention tested, at a pooled odds ratio of 0.15 for new incidence in healthy children.

Mechanism Target:

Dietary T-2 Toxin Exposure — Acts on the toxin exposure directly by removing the contaminated food source.

Show evidence (2 references)

PMID:31490368 SUPPORT Human Clinical

"The pooled odds ratios (ORs) and confidence intervals (95% CIs) for primary prevention new incidence in healthy children following interventions to comprehensive measures, change of grain, salt-rich selenium, and improvements of water were 0.15 (0.02, 0.95), 0.15 (0.03, 0.70), 0.19 (0.09, 0.38),..."

The pooled effect estimates for all four interventions in one sentence - grain change at OR 0.15 for new incidence.

PMID:31490368 SUPPORT Human Clinical

"Comprehensive measures and change of grain were the most effective measures in preventing new case, whereas improvement of water and salt-rich selenium resulted in clinical improvements in children KBD."

The meta-analysis' own ranking, and the useful distinction it draws: grain change prevents new cases, while water and selenium improve existing ones.

Selenium Supplementation

Action: selenium supplementation Ontology label: Nutritional Support NCIT:C15433

Agent: selenium CHEBI:27568

Platform: Small molecule

Selenium-enriched salt and other selenium supplementation. The evidence pulls in two directions and both halves are curated here: two meta-analyses find it prevents new cases and improves radiographic structure in children, while the one randomised trial done in Tibet found it did nothing for established disease, growth or thyroid function once iodine deficiency was corrected. That last result is a real constraint on reading selenium deficiency as the whole story.

Mechanism Target:

Selenoenzyme Antioxidant Capacity Deficit — Restoring selenium restores the substrate for selenoprotein synthesis, which is the node this treatment targets.

Show evidence (5 references)

PMID:31490368 SUPPORT Human Clinical

"The pooled odds ratios (ORs) and confidence intervals (95% CIs) for primary prevention new incidence in healthy children following interventions to comprehensive measures, change of grain, salt-rich selenium, and improvements of water were 0.15 (0.02, 0.95), 0.15 (0.03, 0.70), 0.19 (0.09, 0.38),..."

The primary-prevention estimate for selenium-rich salt, OR 0.19.

PMID:18693119 SUPPORT Human Clinical

"The pooled Peto-OR and NNT favoring selenium supplement was 0.13 (95% CI: 0.04-0.47) and 21 in RCTs, and 0.16 (95% CI: 0.09-0.30) and 26 in non-RCTs."

An independent meta-analysis of the preventive effect, with a number needed to treat of 21 in the randomised trials.

PMID:31376086 SUPPORT Human Clinical

"In children or adolescents, selenium (risk ratio 1.88, 95% confidence interval (CI) 1.51-2.33), vitamin C (2.03, 1.40-2.95) and aspirin (2.14, 1.12-4.08) were effective for radiographic structure improvement."

The network meta-analysis result for radiographic structure improvement in children, alongside vitamin C and aspirin.

+ 2 more references

Drinking Water Improvement

Action: improvement of the drinking water supply Ontology label: Preventive Intervention NCIT:C15843

Platform: Other

Replacing shallow-well water with a cleaner supply. It works - and it is the intervention the food-borne hypotheses do not predict, which is why the water-organic-poisoning hypothesis is curated as ALTERNATIVE rather than retired.

Mechanism Target:

Fulvic Acid Free-Radical Generation in Cartilage — Curated against the fulvic-acid node, which is the mechanism the intervention is supposed to interrupt. The link is hypothesised rather than demonstrated: replacing a water supply changes more than its organic content.

Show evidence (2 references)

PMID:31490368 SUPPORT Human Clinical

"The pooled odds ratios (ORs) and confidence intervals (95% CIs) for primary prevention new incidence in healthy children following interventions to comprehensive measures, change of grain, salt-rich selenium, and improvements of water were 0.15 (0.02, 0.95), 0.15 (0.03, 0.70), 0.19 (0.09, 0.38),..."

The primary-prevention estimate for water improvement, OR 0.20.

PMID:31490368 SUPPORT Human Clinical

"Comprehensive measures and change of grain were the most effective measures in preventing new case, whereas improvement of water and salt-rich selenium resulted in clinical improvements in children KBD."

Places water improvement among the measures that improve existing disease.

Iodine Replacement

Action: iodine supplementation Ontology label: Nutritional Support NCIT:C15433

Agent: iodine CHEBI:24859

Platform: Small molecule

Iodised oil in the Tibetan endemic area. The one intervention in this entry that produced a measured growth response: children who received iodine recovered height-for-age, and unsupplemented controls did not.

Mechanism Target:

Iodine Deficiency and Hypothyroidism — Corrects the deficiency this node describes.

Show evidence (1 reference)

PMID:12816783 SUPPORT Human Clinical

"Height-for-age z scores increased significantly in the subjects who received placebo and iodine or selenium and iodine. In contrast, unsupplemented control subjects did not recover from growth retardation."

Evidence for the link: every arm that received iodine recovered height-for-age and the unsupplemented controls did not, which is the treatment acting on this node rather than on the disease as a whole.

Show evidence (2 references)

PMID:12816783 SUPPORT Human Clinical

"Height-for-age z scores increased significantly in the subjects who received placebo and iodine or selenium and iodine. In contrast, unsupplemented control subjects did not recover from growth retardation."

The growth response, and its control arm. Note the trial was not designed to test iodine against no iodine - every supplemented arm received it - so the comparison is with unsupplemented controls.

PMID:9770558 SUPPORT INDIRECT Human Clinical

"In areas where severe selenium deficiency is endemic, iodine deficiency is a risk factor for Kashin-Beck disease."

Graded INDIRECT: the observational study establishes the risk factor this treatment addresses, not the treatment's effect.

Chondroitin and Glucosamine

Action: Pharmacotherapy NCIT:C15986

Agent: chondroitin sulfate CHEBI:37397 glucosamine CHEBI:5417

Platform: Small molecule

The best-performing symptomatic treatment for adults in the network meta-analysis of KBD treatments, on a standardised mean difference of 1.46 for pain against placebo. An earlier draft of this entry recorded no adult treatment at all, which was wrong.

Mechanism Target:

MODULATES Secondary Degenerative Arthropathy — Symptomatic: it treats the adult arthropathy without acting on any upstream node in this graph.

Show evidence (2 references)

PMID:31376086 SUPPORT Human Clinical

"In adults, chondroitin plus glucosamine was the best for pain (standardised mean difference 1.46, 95% CI 1.07-1.85), followed by intra-articular injection of hyaluronic acid (IAH) (1.09, 0.70-1.48), chondroitin (0.84, 0.47-1.21), diclofenac (0.63, 1.18-1.08), naproxen (0.55, 0.12-0.98),..."

The ranked effect estimates, with this combination at the top.

PMID:31376086 SUPPORT Human Clinical

"Chondroitin, glucosamine, IAH and nonsteroid anti-inflammatory drugs are effective for symptom improvements of KBD in adults."

The review's own conclusion for adult symptomatic treatment.

Intra-Articular Hyaluronic Acid

Action: intra-articular hyaluronic acid injection Ontology label: Pharmacotherapy NCIT:C15986

Agent: hyaluronic acid CHEBI:16336

Platform: Small molecule

Ranked second for adult pain in the network meta-analysis, at a standardised mean difference of 1.09 against placebo.

Mechanism Target:

MODULATES Secondary Degenerative Arthropathy — Symptomatic treatment of the adult joint, delivered into the joint itself.

Show evidence (1 reference)

PMID:31376086 SUPPORT Human Clinical

"In adults, chondroitin plus glucosamine was the best for pain (standardised mean difference 1.46, 95% CI 1.07-1.85), followed by intra-articular injection of hyaluronic acid (IAH) (1.09, 0.70-1.48), chondroitin (0.84, 0.47-1.21), diclofenac (0.63, 1.18-1.08), naproxen (0.55, 0.12-0.98),..."

The ranked effect estimates, with intra-articular hyaluronic acid second.

Nonsteroidal Anti-Inflammatory Drugs

Action: Pharmacotherapy NCIT:C15986

Agent: nonsteroidal anti-inflammatory drug NCIT:C257 diclofenac CHEBI:47381 naproxen CHEBI:7476 meloxicam CHEBI:6741

Platform: Small molecule

Diclofenac, naproxen and meloxicam all beat placebo for adult pain in the network meta-analysis, with smaller effects than the nutraceuticals above.

Mechanism Target:

MODULATES Secondary Degenerative Arthropathy — Symptomatic analgesia for the adult arthropathy.

Show evidence (2 references)

PMID:31376086 SUPPORT Human Clinical

"In adults, chondroitin plus glucosamine was the best for pain (standardised mean difference 1.46, 95% CI 1.07-1.85), followed by intra-articular injection of hyaluronic acid (IAH) (1.09, 0.70-1.48), chondroitin (0.84, 0.47-1.21), diclofenac (0.63, 1.18-1.08), naproxen (0.55, 0.12-0.98),..."

The three individual agents and their effect estimates against placebo.

PMID:31376086 SUPPORT Human Clinical

"Chondroitin, glucosamine, IAH and nonsteroid anti-inflammatory drugs are effective for symptom improvements of KBD in adults."

The review's conclusion grouping them with the nutraceuticals as effective for adult symptoms.

Vitamin C and Aspirin for Radiographic Structure in Children

Action: Pharmacotherapy NCIT:C15986

Agent: vitamin C CHEBI:22652 aspirin CHEBI:15365

Platform: Small molecule

Both improved radiographic structure in children in the network meta-analysis, and the same review says the evidence for both is not established. Curated with that contradiction visible rather than resolved.

Mechanism Target:

MODULATES Endochondral Ossification Failure at the Growth Plate — Radiographic structure improvement is a readout of the growth-plate lesion, which is the node this points at. No mechanism is proposed for either agent here.

Show evidence (2 references)

PMID:31376086 SUPPORT Human Clinical

"In children or adolescents, selenium (risk ratio 1.88, 95% confidence interval (CI) 1.51-2.33), vitamin C (2.03, 1.40-2.95) and aspirin (2.14, 1.12-4.08) were effective for radiographic structure improvement."

The effect estimates for both agents on radiographic structure in children.

PMID:31376086 REFUTE Human Clinical

"Evidence of surgical and complementary treatments for symptoms and aspirin and vitamin C for structure has yet to be established."

The same review's key-points list says the efficacy of aspirin and vitamin C has not been established. Graded REFUTE against this record's own claim and curated alongside the positive estimate, because a reader who saw only one of the two sentences would be misled.

Arthrodesis and Reconstructive Surgery of the Damaged Joint

Action: tibiotalocalcaneal arthrodesis Ontology label: Arthrodesis NCIT:C52007

Platform: Surgery

Surgical salvage of an end-stage joint. The curated case is a conservative tibiotalocalcaneal fusion for talar avascular necrosis with ankle and subtalar arthritis in a 50-year-old patient, achieving bony union and a plantigrade foot at four months. Recorded because a disease whose adult burden is fixed joint deformity has a surgical arm, and this entry previously had none.

Mechanism Target:

BYPASSES Secondary Degenerative Arthropathy — Recorded BYPASSES rather than INHIBITS: fusing the joint removes the painful articulation instead of acting on the cartilage degeneration that destroyed it.

Show evidence (1 reference)

PMID:31335683 SUPPORT Human Clinical

"Conservative tibiotalocalcaneal fusion could help preserving much more viable talar body, maintaining most structural integrity of the ankle joint, and achieving a stable and plantigrade foot postoperatively."

Evidence for the link itself rather than for the treatment: what the procedure is credited with is a stable, plantigrade foot and preserved structural integrity, which is the arthropathy being bypassed rather than reversed.

Show evidence (3 references)

PMID:31335683 SUPPORT Human Clinical

"A conservative tibiotalocalcaneal fusion attempting to preserve as much viable talar body as possible was performed using a humeral locking plate and 2 cannulated compression screws."

The procedure this record names, as performed.

PMID:31335683 SUPPORT Human Clinical

"Bone union proved by CT scan and a good alignment of the left limb were achieved at 4-month follow-up postoperatively."

The reported outcome, at four months.

PMID:31376086 REFUTE Human Clinical

"Evidence of surgical and complementary treatments for symptoms and aspirin and vitamin C for structure has yet to be established."

Graded REFUTE against the strength of this record, not against its existence. The network meta-analysis of 44 randomised trials says the efficacy of surgical treatment for this disease has not been established, so what is curated above is a single case report of a technique in use, not evidence that it works.

Conservative Orthotic Management and Activity Restriction

Action: rigid orthosis and activity restriction Ontology label: Rehabilitation NCIT:C15315

Platform: Device

Non-operative management of the painful end-stage joint with a rigid orthosis and reduced loading. Curated with the result it produced in the one case recorded here, which was failure - it is the step that preceded surgery rather than an alternative to it.

Mechanism Target:

MODULATES Secondary Degenerative Arthropathy — Aimed at the pain and loading of the degenerate joint; no mechanism upstream of it is addressed.

Show evidence (1 reference)

PMID:31335683 SUPPORT Human Clinical

"A 50-year-old woman presented with severe pain and limited range of motion in her left ankle and subtalar joint while walking for 2 years."

Evidence for the link: the pain and restricted range of motion in the degenerate ankle and subtalar joint are what the orthosis and activity restriction were applied to.

Show evidence (2 references)

PMID:31335683 REFUTE Human Clinical

"Conservative treatment with rigid orthosis and activity restriction could not help reduce the pain in the left foot."

Graded REFUTE: in the one case curated here the conservative approach did not relieve the pain, which is why the record exists at all. A single case cannot establish that orthotic management is generally ineffective, and this record does not claim it does.

PMID:31335683 SUPPORT Human Clinical

"A 50-year-old woman presented with severe pain and limited range of motion in her left ankle and subtalar joint while walking for 2 years."

The presentation the conservative measures were applied to.

🌍

Environmental Factors

4

Habitual consumption of grain contaminated with Fusarium T-2 trichothecene mycotoxin

Hazard type: BIOLOGICAL

Route: ORAL

Duration: CHRONIC

Exposome domain: SPECIFIC EXTERNAL

No IARC group is recorded: IARC has not classified T-2 toxin in a group this entry would be entitled to assert, and Kashin-Beck disease is not a neoplastic outcome.

Grain grown and stored in endemic highland areas carries T-2 toxin from Fusarium species. The toxin is directly chondrotoxic, and replacing the grain supply is the single most effective preventive measure tested - which is the strongest practical argument that this exposure is doing real causal work rather than travelling with something else.

Show evidence (2 references)

PMID:35304334 SUPPORT Other

"Gradually, four etiological hypotheses have been formed, including water of organic poisoning hypothesis represented by fulvic acid (FA), biogeochemical hypothesis represented by selenium (Se) deficiency, food mycotoxin poisoning hypothesis represented by T-2 toxin poisoning and compound..."

Names the food mycotoxin hypothesis and its representative agent.

PMID:41272335 SUPPORT Other

"Although Kashin-Beck disease (KBD) in China has been effectively controlled through comprehensive measures such as selenium supplementation and grain replacement, the underlying environmental risk factors may still persist."

Establishes that the exposure is monitored as a live risk rather than a historical one, which is why it is curated as a current exposure. Graded OTHER for consistency with the other background sentences quoted here.

Mechanism Target:

TRIGGERS Dietary T-2 Toxin Exposure — Ingested T-2 toxin is the exposure this initiating node describes.

Show evidence (1 reference)

PMID:42103195 SUPPORT Model Organism

"T-2 toxin exposure induced severe articular cartilage degradation, accompanied by intracellular iron overload lipid peroxidation, oxidative stress and distinctive mitochondrial damage characteristic of ferroptosis."

The controlled demonstration that the toxin alone damages articular cartilage.

Residence on selenium-poor soil with correspondingly low dietary selenium

Hazard type: CHEMICAL

Route: ORAL

Duration: CHRONIC

Exposome domain: GENERAL EXTERNAL

`exposure_term` is left unbound. ECTO was searched for a selenium-deficiency exposure and has none: `ECTO:0900038` (exposure to selenium via ingestion), `ECTO:9000950` (exposure to selenium) and `ECTO:9000192` (exposure to selenium ion) all denote the presence of the element, which is the opposite of the exposure here. ECTO does carry the pattern this needs elsewhere - `ECTO:0400019` is "exposure to decreased protein in food" - so an "exposure to decreased selenium in food" term is the natural new-term request, and that template is recorded here so the next curator does not have to rediscover it. A wrong binding would be worse than none.

Endemic areas sit on soils low in selenium, and the population eats what grows there. This is an exposure by absence, which is why it is curated separately from the mycotoxin rather than folded into a single "endemic diet" entry - the interventions that address it, selenium salt and supplementation, are different interventions.

Show evidence (2 references)

PMID:35304334 SUPPORT Other

"Gradually, four etiological hypotheses have been formed, including water of organic poisoning hypothesis represented by fulvic acid (FA), biogeochemical hypothesis represented by selenium (Se) deficiency, food mycotoxin poisoning hypothesis represented by T-2 toxin poisoning and compound..."

Names the biogeochemical selenium-deficiency hypothesis.

PMID:41272335 SUPPORT Human Clinical

"The results showed that the average soil selenium content in both endemic and non-endemic villages across the six provinces was below 0.2 mg/kg."

Curated because it complicates the exposure rather than confirming it: soil selenium was low in endemic *and* non-endemic villages alike, so soil selenium by itself does not mark out where the disease occurs.

Mechanism Target:

PREDISPOSES Chronic Dietary Selenium Deficiency — Recorded PREDISPOSES rather than TRIGGERS: low selenium sets the susceptible state, and the best-characterised animal model needs the toxin on top of it to produce the deep-zone lesion that resembles the human disease.

Show evidence (1 reference)

PMID:22258458 SUPPORT Model Organism

"Chondronecrosis in deep zone of articular cartilage of knee joints was seen in both the low and high T-2 toxin plus selenium-deficient diet groups, these chondronecrotic lesions being very similar to chondronecrosis observed in human KBD."

The lesion that matches human cartilage appears only in the groups given both the toxin and the selenium-deficient diet, which is the evidence for the predisposing rather than triggering role.

Residence in an iodine-deficient highland area

Hazard type: CHEMICAL

Route: ORAL

Duration: CHRONIC

Exposome domain: GENERAL EXTERNAL

`exposure_term` is unbound for the same reason as the selenium entry: `ECTO:9000084` is "exposure to iodine", which denotes the presence of the element rather than its absence, and no decreased-iodine term exists.

In the Tibetan endemic area iodine deficiency is severe and near-universal, and it is the deficiency that survives multivariate adjustment against the disease where serum selenium does not. Curated as a separate exposure because it has its own intervention - iodised oil - with its own measured effect on growth.

Show evidence (2 references)

PMID:9770558 SUPPORT Human Clinical

"In areas where severe selenium deficiency is endemic, iodine deficiency is a risk factor for Kashin-Beck disease."

The study's conclusion naming iodine deficiency as a risk factor for the disease.

PMID:11482536 SUPPORT Other

"Four factors have been convincingly associated with the disease: selenium deficiency, iodine deficiency, grain contamination with mycotoxin-producing fungi, and water pollution with organic material and fulvic acid."

Lists iodine deficiency among the four convincingly associated factors.

Mechanism Target:

PREDISPOSES Iodine Deficiency and Hypothyroidism — The dietary exposure behind the biochemical state this node records.

Show evidence (1 reference)

PMID:9770558 SUPPORT Human Clinical

"When age and sex were controlled for in a multivariate analysis, low urinary iodine, high serum thyrotropin, and low serum thyroxine-binding globulin values were associated with an increased risk of Kashin-Beck disease, but a low serum selenium concentration was not."

Low urinary iodine as an independently associated exposure, with the thyroid markers that go with it.

Fluoride exposure modifying T-2 toxin detoxification

Hazard type: CHEMICAL

Route: ORAL

Duration: CHRONIC

Exposome domain: SPECIFIC EXTERNAL

Fluoride suppresses carboxylesterase 1, the enzyme that hydrolyses T-2 toxin to its less toxic metabolites. Where fluoride exposure is high, the same dietary toxin dose reaches chondrocytes in its most toxic form. Curated as a modifying exposure rather than an initiating one: nothing here says fluoride alone causes the disease.

Show evidence (1 reference)

PMID:35990316 SUPPORT Other

"This study reveals that CES1 is responsible for the hydrolysis of T-2 toxin, and that fluoride impairs CES1-mediated T-2 toxin detoxification to increase its chondrocyte toxicity."

The authors' conclusion across the enzymology and the chondrocyte toxicity assays. Graded OTHER as a conclusion drawn across both.

Mechanism Target:

EXACERBATES Dietary T-2 Toxin Exposure — Acts on the toxin exposure node by blocking its detoxification rather than by adding to the dose.

Show evidence (1 reference)

PMID:35990316 SUPPORT In Vitro

"We identified that recombinant human CES1 was involved in T-2 toxin hydrolysis to generate HT-2 toxin, but not NEO, and NaF repressed the formation of HT-2 toxin."

The biochemical result: recombinant CES1 hydrolyses the toxin and sodium fluoride represses that hydrolysis.

🔬

Biochemical Markers

5

Serum selenium (Decreased)

Pathograph Readouts

Readout Of Chronic Dietary Selenium Deficiency Negative Diagnostic

Low serum selenium reports the dietary deficiency directly. It does not discriminate affected from unaffected residents of the same endemic area.

Show evidence (2 references)

PMID:9770558 SUPPORT Human Clinical

"Severe selenium deficiency was documented in all villages; 38 percent of subjects had serum concentrations of less than 5 ng per milliliter (64 nmol per liter; normal, 60 to 105 ng per milliliter [762 to 1334 nmol per liter])."

The deficiency measured directly, with the reference interval it is measured against - 38% of children below 5 ng/mL against a normal 60-105 ng/mL.

PMID:9770558 REFUTE Human Clinical

"When age and sex were controlled for in a multivariate analysis, low urinary iodine, high serum thyrotropin, and low serum thyroxine-binding globulin values were associated with an increased risk of Kashin-Beck disease, but a low serum selenium concentration was not."

Graded REFUTE against this marker as a diagnostic readout for the disease rather than for the deficiency: in multivariate analysis a low serum selenium was *not* associated with the disease, while the iodine and thyroid markers were. This is the load-bearing negative behind curating an iodine arm at all.

Reference Ranges

60.0–105.0 ng/mL (general assay reference interval quoted by the source; not derived from or stratified to the study cohort)

`loinc_term` is absent: no LOINC lookup was performed for this analyte, and the slot is `recommended` rather than required. The bounds and unit are taken from the cited sentence, not from a laboratory manual. `population` says what this interval is and is not: the source quotes it as the assay's normal range to measure its subjects against, so it is not a Tibetan-children-specific interval and must not be read as one, even though the study that quotes it measured children aged 5 to 15 in rural Tibet.

Show evidence (1 reference)

PMID:9770558 SUPPORT Human Clinical

"Severe selenium deficiency was documented in all villages; 38 percent of subjects had serum concentrations of less than 5 ng per milliliter (64 nmol per liter; normal, 60 to 105 ng per milliliter [762 to 1334 nmol per liter])."

The interval is quoted verbatim in the same sentence as the deficiency measurement - "normal, 60 to 105 ng per milliliter".

Show evidence (1 reference)

PMID:9770558 SUPPORT Human Clinical

"Severe selenium deficiency was documented in all villages; 38 percent of subjects had serum concentrations of less than 5 ng per milliliter (64 nmol per liter; normal, 60 to 105 ng per milliliter [762 to 1334 nmol per liter])."

The measurement, its threshold, and the reference range.

Hair selenium (Decreased)

Pathograph Readouts

Readout Of Chronic Dietary Selenium Deficiency Negative Monitoring

Used to monitor whether the exposure is returning in areas where the disease was controlled. Note it separated endemic from non-endemic villages in only one of six provinces surveyed.

Show evidence (2 references)

PMID:41272335 SUPPORT Human Clinical

"To dynamically assess the selenium exposure levels in humans (using children’s hair selenium as a biomarker) and the selenium status in the external environment (soil selenium and grain selenium) in historical severe endemic areas and adjacent non-endemic areas in China"

States the surveillance use this readout records - children's hair selenium as the human exposure biomarker.

PMID:41272335 SUPPORT INDIRECT Human Clinical

"The overall selenium status in children was at a moderate level; however, hair selenium levels in endemic villages of Sichuan were significantly lower than those in non-endemic villages."

Graded INDIRECT and curated for what it complicates: hair selenium was lower in endemic than non-endemic villages in Sichuan alone, so it tracks the exposure without cleanly marking out where the disease occurs.

Show evidence (1 reference)

PMID:41272335 SUPPORT Human Clinical

"Particularly in Tibet and Sichuan, grain selenium levels remain critically low"

The dietary source the hair measurement integrates - grain selenium still critically low in Tibet and Sichuan.

Urinary iodine (Decreased)

Pathograph Readouts

Readout Of Iodine Deficiency and Hypothyroidism Negative Diagnostic

Low urinary iodine reports the deficiency and, unlike serum selenium, remained associated with the disease after adjustment for age and sex.

Show evidence (2 references)

PMID:9770558 SUPPORT Human Clinical

"When age and sex were controlled for in a multivariate analysis, low urinary iodine, high serum thyrotropin, and low serum thyroxine-binding globulin values were associated with an increased risk of Kashin-Beck disease, but a low serum selenium concentration was not."

The multivariate result this readout rests on.

PMID:9770558 SUPPORT Human Clinical

"hypothyroidism was more frequent (23 percent vs. 4 percent, P=0.01)."

The clinical consequence measured alongside it - hypothyroidism nearly six times as frequent in affected children as in controls.

Reference Ranges

5.0–25.0 ug/dL (general assay reference interval quoted by the source; not derived from or stratified to the study cohort)

Unit recorded in UCUM notation as `ug/dL`; the source writes it "microg per deciliter". `loinc_term` is absent for the same reason as the serum selenium range - no LOINC lookup was performed and the slot is `recommended`. As there, `population` records that this is the assay's general normal range quoted by the source, not an interval derived from the Tibetan cohort it was applied to.

Show evidence (1 reference)

PMID:9770558 SUPPORT Human Clinical

"Of the 557 subjects in whom urinary iodine was measured, 66 percent had a urinary iodine concentration of less than 2 microg per deciliter (157 nmol per liter; normal, 5 to 25 microg per deciliter [394 to 1968 nmol per liter])."

The interval is quoted verbatim in the same sentence as the deficiency measurement - "normal, 5 to 25 microg per deciliter".

Show evidence (1 reference)

PMID:9770558 SUPPORT Human Clinical

"Of the 557 subjects in whom urinary iodine was measured, 66 percent had a urinary iodine concentration of less than 2 microg per deciliter (157 nmol per liter; normal, 5 to 25 microg per deciliter [394 to 1968 nmol per liter])."

The population distribution and the reference interval - two thirds of children below 2 microg/dL against a normal 5-25.

Serum thyrotropin (Increased)

Pathograph Readouts

Readout Of Iodine Deficiency and Hypothyroidism Positive Diagnostic

High serum thyrotropin reports the hypothyroid state this node describes and was independently associated with the disease.

Show evidence (1 reference)

PMID:9770558 SUPPORT Human Clinical

"When age and sex were controlled for in a multivariate analysis, low urinary iodine, high serum thyrotropin, and low serum thyroxine-binding globulin values were associated with an increased risk of Kashin-Beck disease, but a low serum selenium concentration was not."

Names high serum thyrotropin among the independently associated markers.

Show evidence (1 reference)

PMID:9770558 SUPPORT INDIRECT Human Clinical

"hypothyroidism was more frequent (23 percent vs. 4 percent, P=0.01)."

Graded INDIRECT: the sentence reports the hypothyroidism rate rather than the thyrotropin value, and a raised thyrotropin is what defines hypothyroidism here.

Serum thyroxine-binding globulin (Decreased)

Pathograph Readouts

Correlates With Iodine Deficiency and Hypothyroidism Negative Diagnostic

Recorded CORRELATES_WITH rather than READOUT_OF: it was independently associated with the disease in the same model, but this entry curates no account of what it is measuring here.

Show evidence (1 reference)

PMID:9770558 SUPPORT Human Clinical

"When age and sex were controlled for in a multivariate analysis, low urinary iodine, high serum thyrotropin, and low serum thyroxine-binding globulin values were associated with an increased risk of Kashin-Beck disease, but a low serum selenium concentration was not."

Names low serum thyroxine-binding globulin among the independently associated markers.

Show evidence (1 reference)

PMID:9770558 SUPPORT Human Clinical

"When age and sex were controlled for in a multivariate analysis, low urinary iodine, high serum thyrotropin, and low serum thyroxine-binding globulin values were associated with an increased risk of Kashin-Beck disease, but a low serum selenium concentration was not."

The multivariate result, which is the only evidence this entry has for this marker.

🔬

Diagnosis

3

Hand Radiography in Children

Hand radiography is the primary screening measure in endemic areas, and its weak point is specificity: a large survey of 3,193 children found several normal-variant and developmental signs that are read as positive, the commonest being closure reaction of the metaphysis-epiphysis at 14%.

Show evidence (4 references)

PMID:29459762 SUPPORT Human Clinical

"When screening for Kashin-Beck disease (KBD) in children, hand X-ray examination is the most important measure."

States the role of hand radiography in screening, which is what this record describes.

PMID:29459762 SUPPORT Human Clinical

"However, there is high rate of misdiagnosis because of confusing X-ray signs."

The misdiagnosis problem this record records as the method's limitation.

PMID:29459762 SUPPORT Human Clinical

"The confusing X-ray signs included closure reaction of metaphysis-epiphysis (CRME, 14.28%), thumb variation (0.22%), little finger variation (8.89%), the second metacarpal-phalangeal variation (0.13%) and cystic change (3.85%)."

The specific confusing signs and their frequencies in the surveyed children.

+ 1 more reference

Radiographic Grading of the Adult Ankle

In adults the ankle is graded radiographically against the Kellgren-Lawrence scale used for primary osteoarthritis. The grading correlates well with ankle pain and only weakly with the clinical finger grading, so the two scales are not interchangeable.

The same paper reports that ankle radiographic grade correlates only weakly with the clinical grading of the fingers, and that ankle pain and finger grading are essentially uncorrelated. That is recorded here rather than in the description because it qualifies the method rather than describing it.

Show evidence (2 references)

PMID:41342918 SUPPORT Human Clinical

"The study involved 160 adult KBD patients (a total of 320 ankles) as the case group and 170 matched healthy subjects (a total of 340 ankles) as the control group."

The case-control design behind the ankle grading scheme.

PMID:41342918 SUPPORT Human Clinical

"The X-ray grading of adult KBD ankles was conducted using the Kellgren-Lawrence grading as a reference."

The grading standard, and incidentally the reason the adult disease is mistaken for primary osteoarthritis outside endemic areas.

National Diagnostic Standard WS/T 207-2010

China publishes a national diagnostic standard for the disease, and contemporary field studies recruit against it rather than against study-specific criteria.

The standard's own content is not curated here - the text of WS/T 207-2010 was not obtained, and this record cites only the fact of its use. The clinical grading it defines is referred to as degrees I to III in the burden and quality-of-life literature quoted elsewhere in this entry.

Show evidence (1 reference)

PMID:39770964 SUPPORT Human Clinical

"Patients with KBD were enrolled in the KBD group based on a diagnosis of national criteria WS/T 207-2010."

Names the standard and shows it in use as the recruitment criterion.

📈

Progression

2

Childhood Growth-Plate Phase

While the growth plates are open, the disease produces its defining lesions - brachydactyly, enlarged joints, short stature. This is the phase intervention can prevent, and the phase in which selenium and water measures show clinical improvement.

Show evidence (2 references)

PMID:31490368 SUPPORT Human Clinical

"Comprehensive measures and change of grain were the most effective measures in preventing new case, whereas improvement of water and salt-rich selenium resulted in clinical improvements in children KBD."

That the intervention literature is entirely about children is the evidence for treating this as the modifiable phase.

PMID:40963707 SUPPORT Other

"Kashin-Beck disease (KBD) is an endemic osteoarthropathy, which occurs in children aged 3-12, with similarity to osteoarthritis (OA)."

The age window this phase covers.

Adult Degenerative Phase

After growth stops the skeletal deformity is fixed and what continues is joint degeneration - pain, stiffness, and radiographic change graded like osteoarthritis. Adult management is symptomatic: chondroitin, glucosamine, intra-articular hyaluronic acid and NSAIDs relieve symptoms, and every adult treatment curated here targets the arthropathy node rather than anything upstream of it.

Show evidence (2 references)

PMID:41342918 SUPPORT Human Clinical

"This paper aims to establish an X-ray imaging grading for assessing ankle joints in adult Kashin-Beck disease (KBD) and investigate its correlation with clinical grading of finger and ankle pain."

The adult phase as its own clinical problem, with its own grading need.

PMID:31376086 SUPPORT Human Clinical

"Chondroitin, glucosamine, IAH and nonsteroid anti-inflammatory drugs are effective for symptom improvements of KBD in adults."

The adult treatment literature is symptomatic throughout - this is the evidence for the claim in the notes, which an earlier draft asserted without one.

📊

Prevalence

2

China, national surveillance

Annual Incidence 180.0 per 100,000 per year >1 in 1,000 per year

The 2015 national figure of 0.18%, the end point of a twenty-five-year decline from 22.1% in 1990. 0.18% is 180 per 100,000, which is the ABOVE_1_IN_1000 band. The source calls this an incidence, and it is recorded as one: it is a detection rate among the at-risk population under surveillance, so `rate_denominator` is POPULATION_PER_YEAR rather than person-years. Any single year is a snapshot of a disease being actively eliminated.

Show evidence (1 reference)

PMID:31548049 SUPPORT Human Clinical

"National incidences were 22.1% in 1990, 16.0% in 1995, 12.3% in 2000, 5.5% in 2005, 0.38% in 2010, and 0.18 in 2015, respectively."

The full national series, which is more informative than any one year of it.

Endemic areas of China, 2016

Point Prevalence 2548.0 per 100,000 >1 in 1,000

574,925 prevalent patients among the 22,567,600 inhabitants of endemic areas, which is 2,548 per 100,000 or about 2.5%. The denominator is the endemic-area population, not the national one. This is the residual burden and it is the point: incidence has collapsed while the people already damaged remain.

Show evidence (1 reference)

PMID:31548049 SUPPORT Human Clinical

"Although new patients were annually decreased, it still affected 22,567,600 inhabitants and there were 574,925 patients in 2016."

The residual prevalent burden against the at-risk denominator.

🌍

Epidemiology

1

Early-Onset Endemic Distribution with Family Aggregation

The disease starts in childhood, usually between three and twelve years of age, affects both sexes equally, clusters in agricultural areas and within families, and fluctuates year to year. The family clustering is a gene-environment ambiguity rather than a genetic finding: families share genes and also share grain stores and wells.

Show evidence (2 references)

PMID:31548049 SUPPORT Human Clinical

"Epidemiology of the KBD was characterized by early-onset, gender equality, agricultural area, regional discrepancy, family aggregation, annual fluctuation, etc."

The epidemiological signature this record names, in the source's own list.

PMID:40963707 SUPPORT Other

"Kashin-Beck disease (KBD) is an endemic osteoarthropathy, which occurs in children aged 3-12, with similarity to osteoarthritis (OA)."

The onset window. Graded OTHER: a background sentence rather than the study's own result.

⚖️

Clinical Burden

High

The skeletal deformity is permanent and acquired in childhood, and the adult treatment literature is symptomatic throughout - nothing curated here modifies the underlying lesion. Measured quality of life is lower than in osteoarthritis on every domain but economics; depression is present in half of patients; and the national economic burden is quantified. The burden is high on functional impact and duration rather than on mortality.

Show evidence (5 references)

PMID:37143055 SUPPORT Human Clinical

"The QOL of KBD patients was significantly lower than that of OA patients and healthy people."

The comparison this assessment rests on - worse than osteoarthritis, in the same region.

PMID:37143055 SUPPORT Human Clinical

"The average scores for physical functions, activity limitations, support of society, mental health and general health were significantly lower in KBD patients than that in OA patients and healthy people except for economics."

The domain-by-domain result, including the one domain that did not differ.

PMID:40963707 SUPPORT Human Clinical

"Depression was present in 53.2% of patients in our KBD samples."

The mental-health component of the burden.

+ 2 more references

🔀

Differential Diagnoses

2

Conditions with similar clinical presentations that must be differentiated from Kashin-Beck Disease:

Primary Osteoarthritis

Overlapping Features In an adult presenting outside an endemic area, the joint findings are hard to separate from primary osteoarthritis - the same radiographic scale grades both. The discriminators are the childhood onset, the symmetry, the short stature and brachydactyly, and the endemic-area residence history.

Show evidence (2 references)

PMID:41342918 SUPPORT INDIRECT Human Clinical

"The X-ray grading of adult KBD ankles was conducted using the Kellgren-Lawrence grading as a reference."

Graded INDIRECT: that the standard osteoarthritis scale applies is the basis for the confusion, but the sentence does not itself compare the two diagnoses.

PMID:42000119 SUPPORT Other

"Kashin-Beck disease (KBD) primarily impairs the epiphyseal plate in children and adolescents, resulting in enlarged bone ends and short stature."

The discriminating half: a growth-plate disease of childhood, which primary osteoarthritis is not.

Normal Metaphyseal-Epiphyseal Variants on Hand Radiography

Overlapping Features The practical differential in children is not another disease but normal variation. Closure reaction of the metaphysis-epiphysis, little-finger and thumb variation, and cystic change are all read as positive for the disease in population screening, and the commonest of them occurs in one child in seven.

Show evidence (2 references)

PMID:29459762 SUPPORT Human Clinical

"The confusing X-ray signs included closure reaction of metaphysis-epiphysis (CRME, 14.28%), thumb variation (0.22%), little finger variation (8.89%), the second metacarpal-phalangeal variation (0.13%) and cystic change (3.85%)."

The confusing signs and their frequencies, from a survey of 3,193 children.

PMID:29459762 SUPPORT Human Clinical

"However, there is high rate of misdiagnosis because of confusing X-ray signs."

Why they matter - they are the stated cause of the high misdiagnosis rate.

📊

Related Datasets

4

Integration of miRNA in exosomes and single-cell RNA-seq profiles in endemic osteoarthritis, Kashin-Beck disease geo:GSE246097

Serum and chondrocyte exosomal miRNA sequencing integrated with single-cell RNA-seq of patient chondrocytes - the only single-cell resource this session identified for the disease. Typed MULTI_OMICS because it is two assay types analysed together rather than either one alone.

human MULTI OMICS

PMID:38156801

Show evidence (2 references)

GEO:GSE246097 SUPPORT Other

"We isolated serum and chondrocytes-derived exosomes, miRNA sequencing revealed exosomes miRNA profiles and differentially expressed miRNAs (DE-miRNAs) were identified."

The exosomal miRNA half of the series, from GEO's own summary. Graded OTHER: a repository record describing its contents, not a study result.

GEO:GSE246097 SUPPORT Other

"Single-cell RNA sequencing (scRNA-seq) was performed to identify chondrocyte clusters and their gene signatures in KBD."

The single-cell half, which is what makes this series the only one of its kind here.

Comprehensive expression profiles of mRNAs, lncRNAs and miRNAs in Kashin-Beck Disease identified by RNA-sequencing geo:GSE186593

mRNA, lncRNA and miRNA expression profiles from Kashin-Beck disease cartilage.

human BULK RNA SEQ

PMID:34913457

Show evidence (1 reference)

GEO:GSE186593 SUPPORT Other

"RNA‐seq technology to detect the differentially expressed mRNAs, lncRNAs and miRNAs in KBD patients."

The assay and the three RNA classes profiled, from GEO's own summary. Graded OTHER as a repository record rather than a study result.

Human Peripheral blood mononuclear cells (PBMCs): Control vs. Kashin-Beck Disease geo:GSE59446

Peripheral blood mononuclear cell expression profiling, cases versus controls, and the largest of the available series at 200 samples.

human MICROARRAY

The cached record says only "Gene expression analysis", so the assay type is not readable from it, and neither quoted snippet above names it. MICROARRAY is recorded on the GEO series metadata itself, which types the series as "Expression profiling by array" on platform GPL18887.

Show evidence (2 references)

GEO:GSE59446 SUPPORT Other

"Gene expression analysis was conducted of peripheral blood samples from 100 patients with KBD and 100 controls randomly chosen from two KBD-endemic areas"

The design and the sample count. Graded OTHER as a repository record rather than a study result.

GEO:GSE59446 SUPPORT Other

"Objective:To identify an accurate blood-based gene signature for early detection of Kashin-Beck disease (KBD)."

The stated purpose of the series - an early-detection blood signature.

Effects of Selenium-mediated RUNX2 Overexpression and its Transcriptome Alterations on Chondrocyte Injury in Kashin Beck disease geo:GSE311894

RNA-seq of human chondrocytes with lentiviral RUNX2 overexpression versus controls. Note this is an engineered cell model, not patient material: the series title names the disease but the experiment manipulates RUNX2 directly.

human BULK RNA SEQ

PMID:41425094

Listed as a resource, not as support for a claim. The entry curates no RUNX2 pathophysiology node: the series is a lentiviral overexpression model in cultured chondrocytes whose connection to the disease is the authors' own inference, and this entry does not quote the accompanying paper.

Show evidence (2 references)

GEO:GSE311894 SUPPORT Other

"we established a RUNX2 overexpression model using lentiviral transfection in human chondrocytes."

What the experiment actually is, quoted so the caveat in `notes` below is checkable from the record rather than taken on trust. Graded OTHER as a repository record.

GEO:GSE311894 NO_EVIDENCE Other

"These results provide a comprehensive transcriptomic resource for understanding RUNX2-mediated signaling in cartilage degeneration and may contribute to elucidating the molecular pathogenesis of osteoarthropathy such as Kashin-Beck disease."

Graded NO_EVIDENCE deliberately. This is the sentence that connects the series to the disease, and it claims only that the data "may contribute to elucidating" the pathogenesis of osteoarthropathy "such as" Kashin-Beck disease - a resource claim, not a finding about this disease. Recording it as NO_EVIDENCE is why the series carries no pathophysiology node.

🐁

Animal Models

3

T-2 toxin plus selenium-deficient diet rat

Sprague-Dawley rats fed a selenium-deficient diet for four weeks and then exposed to T-2 toxin for four more. The field's workhorse model, and the one that makes the compound-etiology hypothesis tractable: the deep-zone lesion that resembles the human disease appears only in the groups given both.

Species

Rat

Genotype

Wild type

Publication

PMID:22258458

Pathograph links

Mixed-Mode Chondrocyte Death in Deep and Middle Cartilage Zones recapitulates fidelity: moderate observes: tissue Apoptosis and necroptosis co-exist in the middle zone of the model's cartilage, as they do in children with the disease, and the deep-zone chondronecrosis is described as very similar to the human lesion.

Limitations: A four-week rodent exposure is not a childhood in an endemic village, and the model delivers a fixed toxin dose rather than the variable, seasonal contamination of a real grain store. It also cannot address the fulvic-acid or iodine hypotheses, since neither water composition nor iodine status is a variable in it.

Divergences from the human mechanism

temporal scope qualifying

Weeks of controlled feeding stand in for years of intermittent childhood exposure during active growth; the model compresses the timescale the disease is defined on.

boundary omission qualifying

Drinking-water composition and iodine status are outside the model, so it cannot speak to two of the four hypotheses this entry curates.

Show evidence (2 references)

PMID:30680829 SUPPORT Model Organism

"Apoptosis and necroptosis co-existed in the middle zone in this rat KBD model."

The specific correspondence between model and human cartilage - the same two death modes in the same zone.

+ 1 more reference

Endochondral Ossification Failure at the Growth Plate fails to recapitulate fidelity: low observes: tissue The rat's growth-plate chondronecrosis is explicitly not similar to the human lesion, which is the failure this entry records rather than smooths over. The primary report attributes it to the rat's growth plates never closing.

Limitations: The rat does not close its growth plates, so the epiphyseal closure that defines the human childhood disease cannot occur. Any inference from this model to the growth-plate node is therefore unsafe, and the model's value is at the articular cartilage instead.

Divergences from the human mechanism

species mismatch invalidating

Rat epiphyseal growth plates remain open through life. The human disease is defined by damage to a plate that then closes early, and the model has no counterpart to that event.

Show evidence (2 references)

PMID:22258458 REFUTE Model Organism

"However, the chondronecrosis observed in the rat epiphyseal growth plates of animals treated with T-2 toxin alone or T-2 toxin plus selenium-deficient diets were not similar to that found in human KBD."

The negative result stated by the model's own authors, in both the toxin-alone and the combined groups.

+ 1 more reference

Selenoenzyme Antioxidant Capacity Deficit recapitulates fidelity: moderate observes: molecular The model reproduces the biochemical deficit directly: antioxidant enzyme activity and mRNA down, lipid peroxidation up, in both serum and cartilage.

Limitations: The measurements are of the model's own biochemistry; no matching serum or cartilage antioxidant panel from patients is curated in this entry, so the correspondence to human tissue is assumed rather than shown here.

Show evidence (1 reference)

PMID:22294316 SUPPORT Model Organism

"The levels of thiobarbituric acid reactive substances (TBARS), indicative of lipid peroxidation in serum and cartilage, were significantly increased in all experimental groups compared to the normal diet group, while the levels of antioxidants, measured as total antioxidant capacity (T-AOC),..."

The antioxidant and lipid-peroxidation measurements this link rests on.

Show evidence (1 reference)

PMID:35304334 SUPPORT Model Organism

"In conclusion, the rhesus monkeys administrated endemic water and grain were susceptible animals to replicate KBD. The rats treated with T-2 toxin combined with Se/nutrition deficiency could be a suitable and widely used animal model."

The review's assessment of this model as the suitable and widely used one.

Low-nutrition diet plus T-2 toxin rat

A variant of the workhorse model in which the deficient diet is low in protein, iodine and selenium together rather than in selenium alone - which makes it the only model in this entry that includes the iodine arm.

Species

Rat

Genotype

Wild type

Publication

PMID:23701828

Pathograph links

Endochondral Ossification Failure at the Growth Plate partially recapitulates fidelity: moderate observes: tissue Blurred, thin and irregular epiphyseal plates with chondrocyte necrosis and shortened tibias, which the authors read as closely matching the human bone changes.

Limitations: Recorded PARTIALLY_RECAPITULATES rather than RECAPITULATES because the companion model above found rat growth-plate chondronecrosis explicitly unlike the human lesion, and this study does not address that objection. The diet also varies three nutrients at once, so it cannot separate the iodine, protein and selenium contributions it bundles.

Divergences from the human mechanism

species mismatch qualifying

As with the selenium-deficient model, the rat growth plate does not close, so the human disease's defining endpoint has no counterpart.

boundary omission qualifying

Three dietary deficiencies are applied together and no arm varies them independently, so the model cannot attribute its effect to any one.

Show evidence (2 references)

PMID:23701828 SUPPORT Model Organism

"In group D, all epiphyseal plates were blurred, thin, and irregular."

The radiographic plate finding in the combined group.

+ 1 more reference

Rhesus monkey fed endemic water and grain

Monkeys given the actual water and grain from endemic villages, rather than isolated candidate agents. Assessed as the most susceptible species for replicating the disease - and the design is the point: it tests the endemic environment as a whole instead of pre-judging which constituent matters.

Species

Rhesus monkey

Genotype

Wild type

Publication

PMID:35304334

Pathograph links

Dietary T-2 Toxin Exposure recapitulates fidelity: moderate observes: organism Reproduces the disease using the endemic exposure itself rather than a reconstructed one.

Limitations: Because it delivers the whole environment, it cannot say which constituent is responsible - the same strength and weakness. The only source curated for it here is a methods review; the primary reports of the original monkey experiments were not obtained, so the experimental detail is not curated.

Divergences from the human mechanism

contested assumption qualifying

The model assumes the causative agent is present in the endemic water and grain. That is the hypothesis under test, so a positive result supports the compound etiology without discriminating among its parts.

Show evidence (1 reference)

PMID:35304334 SUPPORT Model Organism

"In conclusion, the rhesus monkeys administrated endemic water and grain were susceptible animals to replicate KBD. The rats treated with T-2 toxin combined with Se/nutrition deficiency could be a suitable and widely used animal model."

The review's assessment of the rhesus monkey as the susceptible species.

{ }

Source YAML

click to show

name: Kashin-Beck Disease
creation_date: "2026-09-07T00:00:00Z"
category: Environmental Osteochondropathy
parents:
- Osteochondropathy
- Environmental Disease
disease_term:
  preferred_term: Kashin-Beck disease
  term:
    id: MONDO:0005610
    label: Kashin-Beck disease
synonyms:
- KBD
- Endemic osteoarthropathy
- Big bone disease
description: >-
  Kashin-Beck disease is an endemic osteochondropathy of children and
  adolescents in a narrow belt running from Siberia through northern and
  western China into Tibet. Chondrocytes die in the deep and middle zones of
  the growth plate and articular cartilage; endochondral ossification fails
  where they die, and the result is symmetric shortening of the fingers and
  limbs, enlarged joints, and a degenerative arthropathy that persists for
  life. Onset is in childhood, usually between three and twelve years of age.
  The cause is environmental and, after seventy years, still unsettled: the
  factors most consistently associated with the disease are selenium
  deficiency, iodine deficiency, grain contaminated by the Fusarium
  trichothecene T-2 toxin, and organic matter - chiefly fulvic acid - in
  drinking water, and no single one of them has been shown to be sufficient.
  What is not disputed is that the disease is preventable: changing the grain
  supply, supplementing selenium and improving the water supply each cut
  incidence sharply, and China's national incidence fell from 22.1% in 1990 to
  0.18% in 2015.

mappings:
  icd11f_mappings:
  - term:
      id: icd11f:211396970
      label: Kashin-Beck disease
    mapping_predicate: skos:exactMatch
    mapping_source: MONDO:0005610
    mapping_justification: >-
      MONDO asserts `icd11f:211396970` as a `skos:exactMatch` of MONDO:0005610, and the
      two carry the same label.
  icd10cm_mappings:
  - term:
      id: ICD10CM:M12.1
      label: Kaschin-Beck disease
    mapping_predicate: skos:exactMatch
    mapping_justification: >-
      Curator-asserted, not inherited: MONDO records no ICD-10-CM cross-reference for
      MONDO:0005610 (its coding xrefs are ICD9:716.00/716.06/716.08 and the ICD-11
      Foundation term above). `ICD10CM:M12.1` names this disease under the older
      "Kaschin-Beck" transliteration, which is why the `label` here does not match the
      entry name character for character - it is ICD-10-CM's canonical label and is
      copied exactly.

mechanistic_hypotheses:
- hypothesis_group_id: compound_etiology
  hypothesis_label: Compound etiology - no single sufficient cause
  status: CANONICAL
  description: >-
    The position that the disease requires a combination - most often low
    selenium plus mycotoxin exposure plus a nutritionally marginal diet - and
    that no single factor is sufficient. Curated as the CANONICAL reading
    because it is the one the reproducible animal models and the multivariate
    epidemiology both land on, and because the four single-factor hypotheses
    below are best understood as its components rather than as its rivals.
    Its weakness is the obvious one: it fits everything and predicts least.
  evidence:
  - reference: PMID:35304334
    reference_title: "Animal models of Kashin-Beck disease exposed to environmental risk factors: Methods and comparisons."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Gradually, four etiological hypotheses have been formed, including water of organic poisoning hypothesis represented by fulvic acid (FA), biogeochemical hypothesis represented by selenium (Se) deficiency, food mycotoxin poisoning hypothesis represented by T-2 toxin poisoning and compound etiology theory hypothesis."
    explanation: Names the compound hypothesis as a standing position in its own right.
  - reference: PMID:11482536
    reference_title: "Kashin-Beck disease: from etiology to prevention or from prevention to etiology?"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "This is an indication that a comprehensive and unifying theory is most likely to be multifactorial."
    explanation: >-
      The review's own conclusion after scoring every competing theory against
      a standard set of causality criteria.
  - reference: PMID:11482536
    reference_title: "Kashin-Beck disease: from etiology to prevention or from prevention to etiology?"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Although none of the competing theories prevails when they are compared using a predefined and standard set of causality criteria (temporality, strength of the association, biological gradient, experimental evidence, biological plausibility, coherence, specificity and analogy), none should be discounted."
    explanation: >-
      Why the single-factor hypotheses below are curated as ALTERNATIVE rather
      than retired: none prevails, and none is discountable.
  - reference: PMID:31548049
    reference_title: "Endemic Kashin-Beck disease: A food-sourced osteoarthropathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Multivariate regression analysis suggested that etiology of the KBD was food-related factors such as fungal contamination of grains, selenium deficiency, imbalance of protein intake, etc."
    explanation: >-
      The epidemiological analysis behind it - several food-related factors
      emerging together rather than one dominating.
  - reference: PMID:35304334
    reference_title: "Animal models of Kashin-Beck disease exposed to environmental risk factors: Methods and comparisons."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In conclusion, the rhesus monkeys administrated endemic water and grain were susceptible animals to replicate KBD. The rats treated with T-2 toxin combined with Se/nutrition deficiency could be a suitable and widely used animal model."
    explanation: >-
      The two most successful models are both compound - endemic water plus
      endemic grain in monkeys, and T-2 plus selenium deficiency in rats.

- hypothesis_group_id: selenium_deficiency
  hypothesis_label: Biogeochemical selenium deficiency
  status: ALTERNATIVE
  description: >-
    Endemic areas sit on selenium-poor soils, and low selenium starves the
    selenoenzymes - glutathione peroxidases, thioredoxin reductases,
    selenoprotein S - that defend chondrocytes against oxidative injury.
    Curated ALTERNATIVE rather than CANONICAL because it is a component of the
    compound reading above, not a competitor to it. Its own weaknesses are
    specific: soil selenium is as low in non-endemic villages as in endemic
    ones, and a randomised trial in Tibet found selenium had no effect on
    established disease once iodine deficiency was corrected.
  evidence:
  - reference: PMID:35304334
    reference_title: "Animal models of Kashin-Beck disease exposed to environmental risk factors: Methods and comparisons."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Gradually, four etiological hypotheses have been formed, including water of organic poisoning hypothesis represented by fulvic acid (FA), biogeochemical hypothesis represented by selenium (Se) deficiency, food mycotoxin poisoning hypothesis represented by T-2 toxin poisoning and compound etiology theory hypothesis."
    explanation: Names this hypothesis and the three it competes with.
  - reference: PMID:42275919
    reference_title: "Selenoprotein S deficiency activates Wnt/β-catenin signaling causing impaired terminal chondrocyte differentiation in Kashin-Beck disease."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "SelS deficiency activates Wnt/β-catenin, impairing terminal differentiation and contributing to selenium-deficiency cartilage injury."
    explanation: >-
      A specific selenoprotein loss producing a specific cartilage lesion, which
      is what turns "low selenium" from a correlation into a mechanism.
  - reference: PMID:12816783
    reference_title: "Selenium and iodine supplementation of rural Tibetan children affected by Kashin-Beck osteoarthropathy."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "However, selenium supplementation had no effect on established Kashin-Beck disease, growth, or thyroid function once iodine deficiency was corrected."
    explanation: >-
      Graded REFUTE against the strong form of this hypothesis: in a randomised
      trial in Tibetan children, selenium did nothing for established disease,
      growth or thyroid function once iodine was replaced. It does not refute a
      preventive role, which the same paper is explicit about.

- hypothesis_group_id: t2_mycotoxin
  hypothesis_label: Food mycotoxin poisoning by Fusarium T-2 toxin
  status: ALTERNATIVE
  description: >-
    T-2 toxin, a trichothecene produced by Fusarium species growing on grain
    stored damp, is directly chondrotoxic. It is the arm with the most
    tractable experimental model and the most effective intervention - grain
    replacement. Curated ALTERNATIVE for the same reason as the selenium arm:
    the workhorse rat model needs a selenium-deficient or low-nutrition diet
    alongside the toxin, which is the compound reading rather than this one.
  evidence:
  - reference: PMID:35304334
    reference_title: "Animal models of Kashin-Beck disease exposed to environmental risk factors: Methods and comparisons."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Gradually, four etiological hypotheses have been formed, including water of organic poisoning hypothesis represented by fulvic acid (FA), biogeochemical hypothesis represented by selenium (Se) deficiency, food mycotoxin poisoning hypothesis represented by T-2 toxin poisoning and compound etiology theory hypothesis."
    explanation: Names this hypothesis alongside the others.
  - reference: PMID:42103195
    reference_title: "Deferoxamine alleviates T-2 toxin-induced articular chondrocyte ferroptosis via the Nrf2/xCT/GPX4 axis: Implications for Kashin-Beck disease pathology."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "T-2 toxin exposure induced severe articular cartilage degradation, accompanied by intracellular iron overload lipid peroxidation, oxidative stress and distinctive mitochondrial damage characteristic of ferroptosis."
    explanation: >-
      Direct chondrotoxicity of the toxin in a controlled animal experiment in
      which T-2 toxin was given without a selenium-deficient arm.

- hypothesis_group_id: iodine_deficiency
  hypothesis_label: Iodine deficiency and hypothyroidism
  status: ALTERNATIVE
  description: >-
    The Tibetan arm of the etiology, and the one this entry previously omitted.
    Endemic areas around Lhasa are iodine-deficient as well as selenium-poor,
    and low urinary iodine - not low serum selenium - is the exposure that
    survived multivariate adjustment in the Tibetan survey. Correcting iodine, not
    selenium, was what let growth-retarded children recover height. Curated
    ALTERNATIVE: the epidemiological association is strong and replicated in an
    intervention, but no cartilage-level mechanism linking thyroid status to
    the growth-plate lesion is curated here.
  evidence:
  - reference: PMID:9770558
    reference_title: "Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In areas where severe selenium deficiency is endemic, iodine deficiency is a risk factor for Kashin-Beck disease."
    explanation: The study's own conclusion, and the clearest statement of this hypothesis.
  - reference: PMID:9770558
    reference_title: "Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "When age and sex were controlled for in a multivariate analysis, low urinary iodine, high serum thyrotropin, and low serum thyroxine-binding globulin values were associated with an increased risk of Kashin-Beck disease, but a low serum selenium concentration was not."
    explanation: >-
      The multivariate result that separates the two deficiencies: iodine and
      thyroid markers survived adjustment and serum selenium did not.
  - reference: PMID:11482536
    reference_title: "Kashin-Beck disease: from etiology to prevention or from prevention to etiology?"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Four factors have been convincingly associated with the disease: selenium deficiency, iodine deficiency, grain contamination with mycotoxin-producing fungi, and water pollution with organic material and fulvic acid."
    explanation: >-
      The causality review's list of the four convincingly associated factors,
      which includes iodine deficiency alongside the three this entry already
      curated.

- hypothesis_group_id: fulvic_acid_water
  hypothesis_label: Organic drinking-water poisoning by fulvic acid
  status: ALTERNATIVE
  description: >-
    Humic and fulvic acids in shallow well water are proposed to generate free
    radicals that damage cartilage. The mechanistic work is old but real: fulvic
    acid enhances lipid peroxidation in cartilage cell culture, accumulates in
    bone and cartilage, and its toxicity falls when its hydroxy group is
    blocked. The intervention data keep it alive too - improving the water
    supply measurably reduces incidence, which a purely food-borne model does
    not predict.
  evidence:
  - reference: PMID:35304334
    reference_title: "Animal models of Kashin-Beck disease exposed to environmental risk factors: Methods and comparisons."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Gradually, four etiological hypotheses have been formed, including water of organic poisoning hypothesis represented by fulvic acid (FA), biogeochemical hypothesis represented by selenium (Se) deficiency, food mycotoxin poisoning hypothesis represented by T-2 toxin poisoning and compound etiology theory hypothesis."
    explanation: Names the water organic-poisoning hypothesis and its representative agent.
  - reference: PMID:10090708
    reference_title: "The role of humic substances in drinking water in Kashin-Beck disease in China."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "We hypothesized that FA in drinking water is an etiological factor of Kashin-Beck disease and that the mechanism of action involves the oxy and hydroxy groups in FA for the generation of free radicals."
    explanation: The hypothesis as its authors stated it, with the chemistry they proposed for it.
  - reference: PMID:31490368
    reference_title: "Prevention and control strategies for children Kashin-Beck disease in China: A systematic review and meta-analysis."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "The pooled odds ratios (ORs) and confidence intervals (95% CIs) for primary prevention new incidence in healthy children following interventions to comprehensive measures, change of grain, salt-rich selenium, and improvements of water were 0.15 (0.02, 0.95), 0.15 (0.03, 0.70), 0.19 (0.09, 0.38), and 0.20 (0.09, 0.42), respectively."
    explanation: >-
      Graded INDIRECT: water improvement reducing incidence is consistent with a
      waterborne agent but does not identify one, since changing the water
      supply changes more than its fulvic acid content.

pathophysiology:
- name: Chronic Dietary Selenium Deficiency
  description: >-
    A child in an endemic area eats grain grown on selenium-poor soil, and
    circulating and cartilage selenium stay low through the years the growth
    plates are open. Curated as its own node rather than bundled with the
    toxin exposure, because the two have different exposure routes, different
    interventions, and different edges out of this graph.
  biological_scale: ORGANISM
  downstream:
  - target: Selenoenzyme Antioxidant Capacity Deficit
    causal_link_type: DIRECT
    hypothesis_groups:
    - selenium_deficiency
    - compound_etiology
  - target: Selenoprotein S Loss and Wnt Derepression
    causal_link_type: DIRECT
    hypothesis_groups:
    - selenium_deficiency
  evidence:
  - reference: PMID:31548049
    reference_title: "Endemic Kashin-Beck disease: A food-sourced osteoarthropathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Multivariate regression analysis suggested that etiology of the KBD was food-related factors such as fungal contamination of grains, selenium deficiency, imbalance of protein intake, etc."
    explanation: The multivariate epidemiological result naming selenium deficiency among the food-related factors.
  - reference: PMID:41272335
    reference_title: "Investigation of Selenium and T-2 Toxin Exposure Levels in the Internal and External Environments of Key Areas of Kashin Beck Disease in China."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The results showed that the average soil selenium content in both endemic and non-endemic villages across the six provinces was below 0.2 mg/kg."
    explanation: >-
      Curated because it complicates the exposure rather than confirming it:
      soil selenium was low in endemic and non-endemic villages alike.

- name: Dietary T-2 Toxin Exposure
  description: >-
    The other half of the initiating state: T-2 toxin from Fusarium growing on
    damp-stored grain, ingested over years. Separated from the selenium node
    because the experimental evidence separates them - T-2 toxin alone degrades
    articular cartilage in the rat, and the deep-zone lesion that actually
    resembles the human disease is the one that needs both.
  biological_scale: ORGANISM
  downstream:
  - target: Chondrocyte Oxidative Stress
    causal_link_type: DIRECT
    hypothesis_groups:
    - t2_mycotoxin
    - compound_etiology
  - target: Ferroptotic Chondrocyte Death
    causal_link_type: DIRECT
    hypothesis_groups:
    - t2_mycotoxin
    description: >-
      The toxin reaches ferroptosis without going through the selenium arm,
      which is why the two hypotheses can each stand alone and also combine.
  evidence:
  - reference: PMID:35304334
    reference_title: "Animal models of Kashin-Beck disease exposed to environmental risk factors: Methods and comparisons."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The main etiological mechanism for Kashin-Beck disease (KBD) is deep chondrocyte necrosis induced by environmental risk factors (ERFs)."
    explanation: >-
      States the field's summary of what initiates the disease - environmental
      risk factors producing deep chondrocyte necrosis.
  - reference: PMID:42103195
    reference_title: "Deferoxamine alleviates T-2 toxin-induced articular chondrocyte ferroptosis via the Nrf2/xCT/GPX4 axis: Implications for Kashin-Beck disease pathology."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "T-2 toxin exposure induced severe articular cartilage degradation, accompanied by intracellular iron overload lipid peroxidation, oxidative stress and distinctive mitochondrial damage characteristic of ferroptosis."
    explanation: The toxin alone degrading articular cartilage in a controlled experiment.

- name: Iodine Deficiency and Hypothyroidism
  description: >-
    In the Tibetan endemic area iodine deficiency is severe enough to produce
    goitre in nearly half of children and biochemical hypothyroidism in a
    quarter of those with the disease, and it is the exposure that survives
    multivariate adjustment where serum selenium does not. Curated as an
    initiating node because the interventional evidence points the same way -
    growth-retarded children recovered height when iodine was replaced, whether
    or not they also received selenium.
  biological_scale: ORGANISM
  downstream:
  - target: Symmetric Growth Arrest and Joint Deformity
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - iodine_deficiency
    description: >-
      Recorded INDIRECT_UNKNOWN_INTERMEDIATES on purpose. Thyroid hormone is
      required for growth-plate maturation, but this entry curates no cartilage
      -level evidence connecting the two in this disease; what it has is an
      epidemiological association and a growth response to iodine replacement.
    evidence:
    - reference: PMID:12816783
      reference_title: "Selenium and iodine supplementation of rural Tibetan children affected by Kashin-Beck osteoarthropathy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Height-for-age z scores increased significantly in the subjects who received placebo and iodine or selenium and iodine. In contrast, unsupplemented control subjects did not recover from growth retardation."
      explanation: >-
        The growth response tracks iodine, not selenium: every arm that received
        iodine gained height and the unsupplemented controls did not.
  evidence:
  - reference: PMID:9770558
    reference_title: "Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Among the 575 subjects, 280 (49 percent) had Kashin-Beck disease, 267 (46 percent) had goiter"
    explanation: The co-occurrence of the disease and goitre in the same survey population.
  - reference: PMID:9770558
    reference_title: "Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "When age and sex were controlled for in a multivariate analysis, low urinary iodine, high serum thyrotropin, and low serum thyroxine-binding globulin values were associated with an increased risk of Kashin-Beck disease, but a low serum selenium concentration was not."
    explanation: >-
      The result this node rests on - low urinary iodine associated with the
      disease after adjustment, low serum selenium not.

- name: Fulvic Acid Free-Radical Generation in Cartilage
  description: >-
    The mechanism proposed for the water-organic-poisoning hypothesis: oxy and
    hydroxy groups on fulvic acid interact with the chondrocyte membrane and
    drive lipid peroxidation, and fulvic acid concentrates in the two tissues
    selenium does not reach. Curated as a node so the ALTERNATIVE hypothesis
    tags a real edge rather than standing outside the graph, and because the
    water-improvement intervention now has somewhere to point.
  biological_scale: MOLECULAR
  downstream:
  - target: Chondrocyte Oxidative Stress
    causal_link_type: DIRECT
    hypothesis_groups:
    - fulvic_acid_water
  evidence:
  - reference: PMID:10090708
    reference_title: "The role of humic substances in drinking water in Kashin-Beck disease in China."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Cartilage cell culture experiments indicated that the oxy or hydroxy functional groups in FA may interfere with the cell membrane and result in enhancement of lipid peroxidation."
    explanation: The cartilage cell-culture result behind the free-radical mechanism.
  - reference: PMID:10090708
    reference_title: "The role of humic substances in drinking water in Kashin-Beck disease in China."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "FA accumulated in bone and cartilage, where selenium rarely concentrates."
    explanation: >-
      The tissue distribution that makes the proposal specific to this disease -
      fulvic acid reaches bone and cartilage, where selenium does not.
  notes: >-
    The supporting work is from 1999 and has not been replicated with modern
    methods, which is why the hypothesis it serves is curated ALTERNATIVE. It is
    recorded here rather than omitted because the alternative - a hypothesis
    group that tags no edge - hides the disagreement this entry exists to show.

- name: Selenoenzyme Antioxidant Capacity Deficit
  description: >-
    Without selenium the selenoproteins cannot be made, and chondrocytes lose
    the antioxidant capacity they rely on. Measured directly in the rat model as
    reduced total antioxidant capacity, catalase, superoxide dismutase and
    glutathione peroxidase in serum and cartilage, at both activity and mRNA
    level, and in patient cartilage as loss of GPx6 from the deep zone.
  biological_scale: MOLECULAR
  biological_processes:
  - preferred_term: cellular oxidant detoxification
    modifier: DECREASED
    term:
      id: GO:0098869
      label: cellular oxidant detoxification
  molecular_functions:
  - preferred_term: glutathione peroxidase activity
    modifier: DECREASED
    term:
      id: GO:0004602
      label: glutathione peroxidase activity
  genes:
  - preferred_term: GPX6
    term:
      id: hgnc:4558
      label: GPX6
  downstream:
  - target: Chondrocyte Oxidative Stress
    causal_link_type: DIRECT
    hypothesis_groups:
    - selenium_deficiency
  evidence:
  - reference: PMID:22294316
    reference_title: "Oxidant damage in Kashin-Beck disease and a rat Kashin-Beck disease model by employing T-2 toxin treatment under selenium deficient conditions."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The levels of thiobarbituric acid reactive substances (TBARS), indicative of lipid peroxidation in serum and cartilage, were significantly increased in all experimental groups compared to the normal diet group, while the levels of antioxidants, measured as total antioxidant capacity (T-AOC), catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidases (GPX), in serum and cartilage were significantly lower than that in the normal diet group."
    explanation: >-
      The measurement this node is named for - antioxidant capacity down and
      lipid peroxidation up in serum and cartilage of the model.
  - reference: PMID:22294316
    reference_title: "Oxidant damage in Kashin-Beck disease and a rat Kashin-Beck disease model by employing T-2 toxin treatment under selenium deficient conditions."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The mRNA expression of those antioxidants in cartilage tissue was significantly reduced by T-2 toxin alone or by selenium-deficient diet plus T-2 toxin treatment."
    explanation: >-
      The loss is transcriptional as well as functional, and the toxin alone is
      enough to produce it.
  - reference: PMID:42384133
    reference_title: "GPx6 downregulation drives ferroptosis in Kashin-Beck disease chondrocytes via the SLC7A11/GPx4 axis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In articular cartilage from children with KBD, GPx6 expression was markedly reduced"
    explanation: >-
      The same deficit in patient cartilage, and zone-matched to where the
      chondrocytes die.

- name: Selenoprotein S Loss and Wnt Derepression
  description: >-
    Selenoprotein S loss de-represses Wnt/beta-catenin signalling and derails
    terminal chondrocyte differentiation. Curated as its own node rather than
    folded into the antioxidant deficit above, because it is a different lesion
    with a different route out of the graph: it reaches the growth plate through
    failed differentiation rather than through oxidant damage.
  biological_scale: MOLECULAR
  biological_processes:
  - preferred_term: canonical Wnt signaling pathway
    modifier: INCREASED
    term:
      id: GO:0060070
      label: canonical Wnt signaling pathway
  - preferred_term: terminal chondrocyte differentiation
    modifier: DECREASED
    term:
      id: GO:0002062
      label: chondrocyte differentiation
  genes:
  - preferred_term: SELENOS
    term:
      id: hgnc:30396
      label: SELENOS
  downstream:
  - target: Endochondral Ossification Failure at the Growth Plate
    causal_link_type: DIRECT
    hypothesis_groups:
    - selenium_deficiency
  evidence:
  - reference: PMID:42275919
    reference_title: "Selenoprotein S deficiency activates Wnt/β-catenin signaling causing impaired terminal chondrocyte differentiation in Kashin-Beck disease."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "SelS deficiency activates Wnt/β-catenin, impairing terminal differentiation and contributing to selenium-deficiency cartilage injury."
    explanation: >-
      Establishes the selenoprotein-to-cartilage link with a knockout, and names
      the specific pathway it runs through.
  notes: >-
    `GO:0002062` (chondrocyte differentiation) is broader than the claim - GO has no
    term for the terminal, hypertrophic step alone - so the specificity is carried in
    `preferred_term` rather than manufactured in the binding.

- name: Chondrocyte Oxidative Stress
  description: >-
    The convergence point of every arm of the etiology. Oxidant load rises in
    chondrocytes because their selenoenzyme defences are depleted, because the
    toxin generates radicals, because fulvic acid drives membrane lipid
    peroxidation, or in some combination.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: chondrocyte
    term:
      id: CL:0000138
      label: chondrocyte
  biological_processes:
  - preferred_term: response to oxidative stress
    modifier: INCREASED
    term:
      id: GO:0006979
      label: response to oxidative stress
  downstream:
  - target: Smad2 and Smad3 Depletion
    causal_link_type: DIRECT
  - target: Chondrocyte Mitochondrial Dysfunction
    causal_link_type: DIRECT
  - target: Ferroptotic Chondrocyte Death
    causal_link_type: DIRECT
    hypothesis_groups:
    - t2_mycotoxin
  evidence:
  - reference: PMID:33769459
    reference_title: "Reduction of Smad2 caused by oxidative stress leads to necrotic death of hypertrophic chondrocytes associated with an endemic osteoarthritis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The occurrence and development of an endemic OA, Kashin-Beck disease (KBD), is closely related to oxidative stress induced by free radicals."
    explanation: >-
      The framing the paper opens with. Graded OTHER: it states the field's
      position rather than the study's own measurement.
  - reference: PMID:33769459
    reference_title: "Reduction of Smad2 caused by oxidative stress leads to necrotic death of hypertrophic chondrocytes associated with an endemic osteoarthritis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "These studies reveal that oxidative stress causes necrosis of hypertrophic chondrocytes by downregulating Smad2 protein, which increases the pathogenesis of KBD cartilage."
    explanation: >-
      The paper's conclusion, which is the edge from this node to the next one.
      Graded OTHER because the conclusion rests on in vitro and in vivo results
      together and no single evidence source describes it.
  - reference: PMID:22294316
    reference_title: "Oxidant damage in Kashin-Beck disease and a rat Kashin-Beck disease model by employing T-2 toxin treatment under selenium deficient conditions."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The levels of thiobarbituric acid reactive substances (TBARS), indicative of lipid peroxidation in serum and cartilage, were significantly increased in all experimental groups compared to the normal diet group, while the levels of antioxidants, measured as total antioxidant capacity (T-AOC), catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidases (GPX), in serum and cartilage were significantly lower than that in the normal diet group."
    explanation: The oxidant load measured directly in cartilage of the compound rat model.

- name: Chondrocyte Mitochondrial Dysfunction
  description: >-
    Respiratory chain complexes II to V run at reduced activity in chondrocytes
    taken from adult patients, ATP falls, membrane potential collapses and
    cytochrome c is released with caspase-9 and caspase-3 activation. This is
    the intrinsic apoptotic route into the mixed cell death below, and the one
    measured in human cells rather than inferred from a model.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: chondrocyte
    term:
      id: CL:0000138
      label: chondrocyte
  biological_processes:
  - preferred_term: mitochondrial electron transport chain activity
    modifier: DECREASED
    term:
      id: GO:0022900
      label: electron transport chain
  downstream:
  - target: Mixed-Mode Chondrocyte Death in Deep and Middle Cartilage Zones
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:20650322
    reference_title: "Mitochondrial function is altered in articular chondrocytes of an endemic osteoarthritis, Kashin-Beck disease."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Activities of complexes II, III, IV and V were reduced in KBD articular chondrocytes compared with cells from normal controls."
    explanation: >-
      The respiratory-chain measurement this node records, in chondrocytes
      cultured from patients.
  - reference: PMID:20650322
    reference_title: "Mitochondrial function is altered in articular chondrocytes of an endemic osteoarthritis, Kashin-Beck disease."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Cultured KBD chondrocytes had a reduction of cellular ATP levels and contained a higher proportion of cells with de-energized mitochondria."
    explanation: The functional consequence - less ATP, and more de-energized mitochondria.
  - reference: PMID:20650322
    reference_title: "Mitochondrial function is altered in articular chondrocytes of an endemic osteoarthritis, Kashin-Beck disease."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Mitochondrial cytochrome c release and activation of caspase-9 and 3 were also observed."
    explanation: >-
      The intrinsic apoptotic route out of this node, which is the edge to the
      mixed-mode death below.
  - reference: PMID:20650322
    reference_title: "Mitochondrial function is altered in articular chondrocytes of an endemic osteoarthritis, Kashin-Beck disease."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "These findings suggest the involvement of mitochondrial function and apoptotic cell death in the pathophysiology of KBD."
    explanation: >-
      The authors' own placement of the finding in the disease. Graded OTHER as
      an interpretation rather than a measurement.
  notes: >-
    `GO:0022900` (electron transport chain) is not mitochondrion-specific and is
    therefore broader than the claim; the measurement is of respiratory complexes II-V
    in chondrocyte mitochondria, and that specificity is carried in `preferred_term`.

- name: Smad2 and Smad3 Depletion
  description: >-
    Oxidative stress strips Smad2 and Smad3 from hypertrophic chondrocytes, and
    the two losses produce different deaths - Smad2 loss necrosis, Smad3 loss
    apoptosis. This is the cleanest molecular account of why the cell death in
    this disease is mixed rather than of one type.
  biological_scale: MOLECULAR
  cell_types:
  - preferred_term: hypertrophic chondrocyte
    term:
      id: CL:0000743
      label: hypertrophic chondrocyte
  downstream:
  - target: Mixed-Mode Chondrocyte Death in Deep and Middle Cartilage Zones
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:33769459
    reference_title: "Reduction of Smad2 caused by oxidative stress leads to necrotic death of hypertrophic chondrocytes associated with an endemic osteoarthritis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Reduction of Smad2 protein induced necrotic death of hypertrophic chondrocytes, while reduction of Smad3 protein induced apoptosis."
    explanation: >-
      The dissociation this node records: two related proteins, two different
      modes of death.
  - reference: PMID:33769459
    reference_title: "Reduction of Smad2 caused by oxidative stress leads to necrotic death of hypertrophic chondrocytes associated with an endemic osteoarthritis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In the cartilage of KBD patients, the expression of Smad2 and Smad3 proteins in the middle and deep zone was significantly decreased with an observed full deletion in the deep zone of some samples."
    explanation: >-
      The same depletion in patient cartilage, zone by zone, which is what makes
      the in vitro result relevant to the human disease.

- name: Ferroptotic Chondrocyte Death
  description: >-
    T-2 toxin drives iron overload and lipid peroxidation in articular
    chondrocytes by suppressing the Nrf2/xCT/GPX4 axis, and loss of GPx6 sits
    upstream of the same axis in patient cartilage. Curated as its own node
    because it is pharmacologically separable: an iron chelator reverses it.
  biological_scale: CELLULAR
  biological_processes:
  - preferred_term: ferroptosis
    modifier: INCREASED
    term:
      id: GO:0097707
      label: ferroptosis
  downstream:
  - target: Mixed-Mode Chondrocyte Death in Deep and Middle Cartilage Zones
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:42103195
    reference_title: "Deferoxamine alleviates T-2 toxin-induced articular chondrocyte ferroptosis via the Nrf2/xCT/GPX4 axis: Implications for Kashin-Beck disease pathology."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Our findings demonstrate that T-2 toxin induces ferroptosis in articular chondrocytes, at least partially, through the suppression of the Nrf2/xCT/GPX4 axis."
    explanation: The mechanism and the axis it runs through.
  - reference: PMID:42103195
    reference_title: "Deferoxamine alleviates T-2 toxin-induced articular chondrocyte ferroptosis via the Nrf2/xCT/GPX4 axis: Implications for Kashin-Beck disease pathology."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "T-2 toxin exposure induced severe articular cartilage degradation, accompanied by intracellular iron overload lipid peroxidation, oxidative stress and distinctive mitochondrial damage characteristic of ferroptosis."
    explanation: The phenotype, including the mitochondrial morphology that identifies ferroptosis.
  - reference: PMID:42384133
    reference_title: "GPx6 downregulation drives ferroptosis in Kashin-Beck disease chondrocytes via the SLC7A11/GPx4 axis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Gpx6 knockout mice exhibited signs of ECM degradation in articular cartilage, along with an enhanced susceptibility to T-2 toxin exposure."
    explanation: >-
      A knockout of the selenoenzyme that sits upstream of the axis reproduces
      matrix degradation and sensitises the animal to the toxin, which links the
      selenium arm to this toxin-driven node.

- name: Mixed-Mode Chondrocyte Death in Deep and Middle Cartilage Zones
  description: >-
    Chondrocytes die by several mechanisms at once and the mechanisms sort by
    cartilage zone: necroptosis dominates the middle zone in children, frank
    necrosis the deep zone. Caspase-3 is not raised, so classic apoptosis is not
    the whole story. This entry does not force a single mode.
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: chondrocyte
    term:
      id: CL:0000138
      label: chondrocyte
  biological_processes:
  - preferred_term: necroptotic process
    modifier: INCREASED
    term:
      id: GO:0070266
      label: necroptotic process
  - preferred_term: apoptotic process
    modifier: INCREASED
    term:
      id: GO:0006915
      label: apoptotic process
  downstream:
  - target: Endochondral Ossification Failure at the Growth Plate
    causal_link_type: DIRECT
  - target: Articular Cartilage Matrix Degradation
    causal_link_type: DIRECT
  - target: Type H Vessel Proliferation at the Epiphyseal Plate
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      The inflammation accompanying chondrocyte injury upregulates IL-6 and
      SELE, which drives the vascular response.
  evidence:
  - reference: PMID:30680829
    reference_title: "Death of chondrocytes in Kashin-Beck disease: Apoptosis, necrosis or necroptosis?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Immunohistochemistry failed to detect significant differences in caspase-3 levels in KBD children compared to controls, suggesting that beside apoptosis necroptosis dominates as a cell death mechanism in the middle zone of cartilage from KBD children."
    explanation: >-
      The negative caspase-3 result and the RIP3 positivity together, which is
      what makes this node "mixed-mode" rather than apoptotic.
  - reference: PMID:30680829
    reference_title: "Death of chondrocytes in Kashin-Beck disease: Apoptosis, necrosis or necroptosis?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Ultrastructural analysis of chondrocyte from deep cartilage revealed abnormal cells with numerous morphological changes, such as plasma membrane breakdown, generalized swelling of the cytoplasm and loss of identifiable organelles."
    explanation: >-
      The ultrastructural necrosis in the deep zone, distinct from the
      middle-zone picture. The cached full text places this analysis in the
      children's cartilage (Figure 5), not in the rat arm the abstract describes
      immediately before it.
  - reference: PMID:30680829
    reference_title: "Death of chondrocytes in Kashin-Beck disease: Apoptosis, necrosis or necroptosis?"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Chondrocyte death plays a key role in either the initiation or the progression of KBD pathogenesis."
    explanation: >-
      Places this node at the centre of the disease rather than downstream of
      it. Graded OTHER: the sentence is the paper's closing interpretation
      rather than one of its measurements.

- name: Type H Vessel Proliferation at the Epiphyseal Plate
  description: >-
    Type H vessels multiply in the growing epiphyseal plate and carry more T-2
    toxin to it, so the vascular response feeds the injury that provoked it.
    The loop is demonstrated in both directions pharmacologically, which is
    unusually strong for a feedback claim.
  biological_scale: TISSUE
  locations:
  - preferred_term: epiphyseal plate
    term:
      id: UBERON:0002516
      label: epiphyseal plate
  downstream:
  - target: Mixed-Mode Chondrocyte Death in Deep and Middle Cartilage Zones
    causal_link_type: DIRECT
    description: >-
      The amplifying limb: more vessels, more toxin delivered to the plate, more
      chondrocyte death.
    evidence:
    - reference: PMID:42000119
      reference_title: "A self-perpetuating cycle of Type H vessel proliferation and T-2 induced inflammation drives KBD pathogenesis."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Roxadustat increased type H vessel density (Mean Difference (MD): 4.11, 95%CI: 0.19, 8.04), amplified T-2 toxin accumulation near the epiphyseal plate (MD: 0.16, 95%CI: 0.062, 0.25) and exacerbated chondrocyte apoptosis and necrosis."
      explanation: >-
        Promoting the vessels worsened toxin accumulation and cell death -
        the forward half of the loop, shown by intervention rather than
        correlation.
  evidence:
  - reference: PMID:42000119
    reference_title: "A self-perpetuating cycle of Type H vessel proliferation and T-2 induced inflammation drives KBD pathogenesis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Conversely, HF reduced type H vessel proliferation (MD: -3.70, 95%CI: -6.67, -0.73), decreased T-2 toxin levels and suppressed inflammation (MD: -0.17, 95%CI: -0.23, -0.11), while preserving proteoglycan content and cartilage morphology."
    explanation: >-
      The mirror-image experiment: inhibiting the vessels reduced toxin,
      inflammation and cartilage damage. Two-directional pharmacology is what
      makes this node causal rather than associated.
  - reference: PMID:42000119
    reference_title: "A self-perpetuating cycle of Type H vessel proliferation and T-2 induced inflammation drives KBD pathogenesis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Single-cell RNA sequencing, qPCR and explants revealed that T-2 toxin-induced inflammation upregulated IL-6 and SELE, promoting type H vessels proliferation."
    explanation: The signalling route from chondrocyte injury to the vascular response.

- name: Articular Cartilage Matrix Degradation
  description: >-
    Alongside the growth-plate lesion, the articular matrix itself is degraded:
    matrix metalloproteinases rise, type II collagen and proteoglycan fall.
    TSG-6 is over-expressed through all three cartilage zones in patients and,
    when silenced, takes the metalloproteinases down with it - so it is a
    driver of the degradation rather than a marker of it.
  biological_scale: TISSUE
  locations:
  - preferred_term: articular cartilage
    term:
      id: UBERON:0010996
      label: articular cartilage of joint
  biological_processes:
  - preferred_term: extracellular matrix disassembly
    modifier: INCREASED
    term:
      id: GO:0022617
      label: extracellular matrix disassembly
  genes:
  - preferred_term: TSG-6
    term:
      id: hgnc:11898
      label: TNFAIP6
  downstream:
  - target: Secondary Degenerative Arthropathy
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:36468025
    reference_title: "Abnormal expression of TSG-6 disturbs extracellular matrix homeostasis in chondrocytes from endemic osteoarthritis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "TSG-6 was upregulated in KBD chondrocytes at the mRNA level and upregulated in the superficial, middle, and deep zones of KBD cartilage."
    explanation: The expression finding in patient cartilage, zone by zone.
  - reference: PMID:36468025
    reference_title: "Abnormal expression of TSG-6 disturbs extracellular matrix homeostasis in chondrocytes from endemic osteoarthritis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Compared with the blank control group, the expression of MMPs was increased in the intervention group of HT-2 toxin, while the expression of proteoglycan and COL2A1 decreased (p < 0.05)."
    explanation: >-
      The toxin metabolite reproducing the matrix picture in chondrocyte
      culture - metalloproteinases up, collagen and proteoglycan down.
  - reference: PMID:36468025
    reference_title: "Abnormal expression of TSG-6 disturbs extracellular matrix homeostasis in chondrocytes from endemic osteoarthritis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "After TSG-6 silencing, the expression of MMP1, MMP3, MMP13, and proteoglycan was significantly decreased while COL2A1 expression was significantly increased, which was reversed after the overexpression of TSG-6 induced by TNF-α (p < 0.05)."
    explanation: >-
      The silencing and rescue experiment, which is what makes TSG-6 a driver of
      the degradation here rather than a marker of it.
  - reference: PMID:36468025
    reference_title: "Abnormal expression of TSG-6 disturbs extracellular matrix homeostasis in chondrocytes from endemic osteoarthritis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The upregulation of the TSG-6 gene may play a role in promoting the damage and degradation of the extracellular matrix in KBD chondrocytes under the exposure of HT-2 toxin."
    explanation: >-
      The authors' reading of their own silencing and overexpression
      experiments. Graded OTHER as a conclusion drawn across both.

- name: Endochondral Ossification Failure at the Growth Plate
  description: >-
    Where the chondrocytes die, the growth plate cannot convert cartilage to
    bone, and ossification becomes irregular. The oldest histology of the
    disease describes the same failure from a different
    angle: the proximal cartilage end plate of the phalanx is unvascularised,
    with epiphyseal bone formation altered around it.
  biological_scale: TISSUE
  locations:
  - preferred_term: epiphyseal plate
    term:
      id: UBERON:0002516
      label: epiphyseal plate
  biological_processes:
  - preferred_term: ossification
    modifier: DECREASED
    term:
      id: GO:0001503
      label: ossification
  downstream:
  - target: Symmetric Growth Arrest and Joint Deformity
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:42000119
    reference_title: "A self-perpetuating cycle of Type H vessel proliferation and T-2 induced inflammation drives KBD pathogenesis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Kashin-Beck disease (KBD) primarily impairs the epiphyseal plate in children and adolescents, resulting in enlarged bone ends and short stature."
    explanation: >-
      States the target tissue and the growth consequence. Graded OTHER: the
      sentence is the paper's framing of the disease rather than its own result.
  - reference: PMID:11482529
    reference_title: "Histology of Kashin-Beck lesions."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The prevailing characteristic of the samples is the absence of vascularisation within the proximal cartilage end plate of the phalanx associated with an alteration of the epiphyseal bone formation."
    explanation: >-
      The histological finding in patient phalanges - no vascularisation of the
      cartilage end plate, and altered epiphyseal bone formation with it.
  - reference: PMID:23701828
    reference_title: "An animal model of Kashin-Beck disease induced by a low-nutrition diet and exposure to T-2 toxin."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In group D, all epiphyseal plates were blurred, thin, and irregular."
    explanation: >-
      The radiographic plate change in the low-nutrition plus T-2 toxin rat -
      blurred, thin and irregular plates, with shortened tibias.

- name: Symmetric Growth Arrest and Joint Deformity
  description: >-
    Because the growth plates fail while the child is still growing, the
    shortening is symmetric and affects the most actively growing bones. The
    clinical result is the triad the disease is recognised by: enlarged finger
    joints, shortened fingers, and short stature.
  biological_scale: ORGANISM
  evidence:
  - reference: PMID:31335683
    reference_title: "Conservative tibiotalocalcaneal fusion for partial talar avascular necrosis in conjunction with ankle and subtalar joint osteoarthritis in Kashin-Beck disease: A case report."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Kashin-Beck disease (KBD) is known for some typical characters like finger joint enlargement, shortened fingers, and dwarfism."
    explanation: >-
      The clinical triad this node produces. Graded OTHER: the sentence is a
      case report's framing of the disease rather than a study result.
  - reference: PMID:23701828
    reference_title: "An animal model of Kashin-Beck disease induced by a low-nutrition diet and exposure to T-2 toxin."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "A rat model of KBD induced by a low-nutrition diet and T-2 toxin exposure demonstrated radiographic and histopathological abnormalities of the proximal epiphyseal plate and the tibial metaphysis that are very similar to the bone changes found in patients with KBD."
    explanation: >-
      The model's own account of the same outcome - plate and metaphyseal
      changes matching those in patients.

- name: Secondary Degenerative Arthropathy
  description: >-
    The articular cartilage damage does not stop when growth does. Adults carry
    a deforming arthropathy with pain and restricted movement, graded
    radiographically much as primary osteoarthritis is - which is also why the
    disease is easy to mistake for it outside endemic areas.
  biological_scale: ORGANISM
  locations:
  - preferred_term: articular cartilage
    term:
      id: UBERON:0010996
      label: articular cartilage of joint
  evidence:
  - reference: PMID:41342918
    reference_title: "Study on radiographic grading of ankle joint in adult patients with Kashin-Beck disease in Shaanxi and Gansu Province, China."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The X-ray grading of adult KBD ankles was conducted using the Kellgren-Lawrence grading as a reference."
    explanation: >-
      That the adult disease is graded on the standard osteoarthritis scale is
      the evidence for treating this as a degenerative arthropathy.

phenotypes:
- category: Skeletal
  name: Short Stature
  description: >-
    Reduced adult height from growth-plate failure during childhood. Severity
    tracks how early the disease started.
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
    onset:
      onset_category: CHILDHOOD
      min_age_years: 3
      max_age_years: 12
  reports_on:
  - target: Symmetric Growth Arrest and Joint Deformity
    relationship: READOUT_OF
  evidence:
  - reference: PMID:42000119
    reference_title: "A self-perpetuating cycle of Type H vessel proliferation and T-2 induced inflammation drives KBD pathogenesis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Kashin-Beck disease (KBD) primarily impairs the epiphyseal plate in children and adolescents, resulting in enlarged bone ends and short stature."
    explanation: >-
      Names short stature as a direct consequence of the growth-plate lesion.
      Graded OTHER as the paper's framing rather than its own measurement.
  - reference: PMID:40963707
    reference_title: "Prevalence and Risk Factors of Depression in Patients With Endemic Osteoarthritis Kashin-Beck Disease."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Kashin-Beck disease (KBD) is an endemic osteoarthropathy, which occurs in children aged 3-12, with similarity to osteoarthritis (OA)."
    explanation: >-
      The onset window recorded on this phenotype. Graded OTHER: a background
      sentence rather than the study's own result.

- category: Skeletal
  name: Brachydactyly
  description: >-
    Shortened, thickened fingers. With enlargement of the finger joints and
    short stature, this is the clinical triad the disease is recognised by, and
    the finger findings are what population screening grades.
  phenotype_term:
    preferred_term: Brachydactyly
    term:
      id: HP:0001156
      label: Brachydactyly
  diagnostic: true
  reports_on:
  - target: Symmetric Growth Arrest and Joint Deformity
    relationship: READOUT_OF
  evidence:
  - reference: PMID:31335683
    reference_title: "Conservative tibiotalocalcaneal fusion for partial talar avascular necrosis in conjunction with ankle and subtalar joint osteoarthritis in Kashin-Beck disease: A case report."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Kashin-Beck disease (KBD) is known for some typical characters like finger joint enlargement, shortened fingers, and dwarfism."
    explanation: >-
      Names shortened fingers among the typical characters of the disease.
      Graded OTHER: a case report's framing rather than a study result.
  - reference: PMID:29459762
    reference_title: "The characteristics of positive and confusing hand X-ray signs in diagnosing Kashin-Beck Disease in children in China."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "When screening for Kashin-Beck disease (KBD) in children, hand X-ray examination is the most important measure."
    explanation: >-
      Graded INDIRECT: that hand radiography is the primary screening measure
      is why the digital findings are treated as the index feature, but the
      sentence does not itself describe shortened fingers.
  notes: >-
    An earlier draft of this record called brachydactyly the earliest sign
    because the phalangeal growth plates are affected first. Neither half of
    that is supported by anything cited here, and it has been removed rather
    than left standing on a plausible-sounding argument.

- category: Skeletal
  name: Enlarged Joints
  description: >-
    Symmetric enlargement of the bone ends. Finger joint enlargement is what
    population screening grades in children; the ankle is the joint graded
    radiographically in adults.
  phenotype_term:
    preferred_term: enlarged bone ends
    term:
      id: HP:0003037
      label: Enlarged joints
  reports_on:
  - target: Endochondral Ossification Failure at the Growth Plate
    relationship: READOUT_OF
  evidence:
  - reference: PMID:42000119
    reference_title: "A self-perpetuating cycle of Type H vessel proliferation and T-2 induced inflammation drives KBD pathogenesis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Kashin-Beck disease (KBD) primarily impairs the epiphyseal plate in children and adolescents, resulting in enlarged bone ends and short stature."
    explanation: >-
      Names enlarged bone ends as a consequence of the epiphyseal-plate lesion.
      Graded OTHER as the paper's framing rather than its own measurement.
  - reference: PMID:31335683
    reference_title: "Conservative tibiotalocalcaneal fusion for partial talar avascular necrosis in conjunction with ankle and subtalar joint osteoarthritis in Kashin-Beck disease: A case report."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Kashin-Beck disease (KBD) is known for some typical characters like finger joint enlargement, shortened fingers, and dwarfism."
    explanation: Names finger joint enlargement among the typical characters of the disease.

- category: Musculoskeletal
  name: Joint Pain
  description: Chronic pain in the affected joints, and the symptom that brings adults to care.
  phenotype_term:
    preferred_term: Arthralgia
    term:
      id: HP:0002829
      label: Arthralgia
  reports_on:
  - target: Secondary Degenerative Arthropathy
    relationship: READOUT_OF
  evidence:
  - reference: PMID:41342918
    reference_title: "Study on radiographic grading of ankle joint in adult patients with Kashin-Beck disease in Shaanxi and Gansu Province, China."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This paper aims to establish an X-ray imaging grading for assessing ankle joints in adult Kashin-Beck disease (KBD) and investigate its correlation with clinical grading of finger and ankle pain."
    explanation: Establishes pain as the clinical endpoint the radiographic grading is correlated against.
  - reference: PMID:31376086
    reference_title: "The effectiveness of treatments for Kashin-Beck disease: a systematic review and network meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In adults, chondroitin plus glucosamine was the best for pain (standardised mean difference 1.46, 95% CI 1.07-1.85), followed by intra-articular injection of hyaluronic acid (IAH) (1.09, 0.70-1.48), chondroitin (0.84, 0.47-1.21), diclofenac (0.63, 1.18-1.08), naproxen (0.55, 0.12-0.98), meloxicam (0.52, 0.03-1.01) and glucosamine (0.40, 0.13-0.67) compared to placebo"
    explanation: >-
      Pain is the primary outcome of the adult treatment literature, which is
      the strongest evidence that it is the dominant adult manifestation.

- category: Musculoskeletal
  name: Joint Stiffness and Restricted Movement
  description: Limited range of motion from deformity and secondary degenerative change.
  phenotype_term:
    preferred_term: Joint stiffness
    term:
      id: HP:0001387
      label: Joint stiffness
  reports_on:
  - target: Secondary Degenerative Arthropathy
    relationship: READOUT_OF
  evidence:
  - reference: PMID:12816783
    reference_title: "Selenium and iodine supplementation of rural Tibetan children affected by Kashin-Beck osteoarthropathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The frequencies of joint pain, decreased joint mobility, and radiologic abnormalities were not significantly different between the 3 groups at 12 mo."
    explanation: >-
      Decreased joint mobility is one of the three outcomes the Tibetan
      supplementation trial measured, which is the evidence that it is a
      standard manifestation. The sentence also records the trial's negative
      result on it.

- category: Musculoskeletal
  name: Sarcopenia Risk
  description: >-
    Adults with the disease screen positive for sarcopenia risk more often than
    propensity-matched non-affected residents of the same endemic area, and the
    disease remains an independent risk factor in multivariate analysis.
  phenotype_term:
    preferred_term: reduced skeletal muscle mass and strength
    term:
      id: HP:0003202
      label: Skeletal muscle atrophy
  reports_on:
  - target: Secondary Degenerative Arthropathy
    relationship: READOUT_OF
  evidence:
  - reference: PMID:39770964
    reference_title: "Kashin-Beck Disease: A Risk Factor for Sarcopenia and Its Interaction with Selenium."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "KBD as an independent risk factor increased the risk of sarcopenia for patients."
    explanation: >-
      The independent association this record names, after propensity-score
      matching within the endemic area.
  notes: >-
    Bound to the closest available HP term. `HP:0003202` names muscle atrophy;
    what was measured is a SARC-F screening score, which is a risk instrument
    rather than a confirmed diagnosis, and `preferred_term` carries that
    distinction.

- category: Neuropsychiatric
  name: Depression
  description: >-
    Depressive symptoms are common in adults with the disease, and are
    associated with pain severity and with comorbid chronic disease.
  phenotype_term:
    preferred_term: Depression
    term:
      id: HP:0000716
      label: Depression
  evidence:
  - reference: PMID:40963707
    reference_title: "Prevalence and Risk Factors of Depression in Patients With Endemic Osteoarthritis Kashin-Beck Disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Depression was present in 53.2% of patients in our KBD samples."
    explanation: >-
      The measured prevalence on PHQ-9 in a field survey of 440 subjects in
      endemic areas of northwest China.
  - reference: PMID:40963707
    reference_title: "Prevalence and Risk Factors of Depression in Patients With Endemic Osteoarthritis Kashin-Beck Disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Being male (odds ratio [OR]: 0.296, 95% confidence interval [CI]: 0.180-0.486, p < 0.001) was an independent protective factor for depression, while the presence of comorbid chronic diseases (OR: 4.701, 95% CI: 2.292-9.640, p < 0.001), and a higher visual analog scale (VAS) pain level (OR: 5.275, 95% CI: 1.326-20.978, p=0.018) were independent risk factors for depression in KBD patients."
    explanation: The associated factors this record names, from the same logistic regression.

histopathology:
- name: Deep-Zone Acellular Areas with Surrounding Chondrocyte Clusters
  description: >-
    The characteristic cartilage picture: patches in the deep zone emptied of
    chondrocytes, ringed by clusters of surviving cells, with the remaining
    cells staining palely. The clustering is the cartilage's attempt to
    repopulate what the necrosis removed.
  finding_term:
    preferred_term: deep-zone chondronecrosis with peripheral chondrocyte clustering
  diagnostic: true
  notes: >-
    `finding_term` is left unbound. NCIT was searched under the Morphologic Finding
    branch and the closest term is `NCIT:C36184` (Necrosis), which names only one
    component of a three-part post-composition - the zone, the acellular patches and
    the compensatory clustering are all lost by it. Binding the bare necrosis term
    would make the record look grounded while discarding what identifies it. No term
    beats a bad one.
  evidence:
  - reference: PMID:30680829
    reference_title: "Death of chondrocytes in Kashin-Beck disease: Apoptosis, necrosis or necroptosis?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In KBD cartilage chondrocyte death was characterized by paler staining of the cells. Multiple chondral cell clusters surrounded the areas lacking cells in the deep zone."
    explanation: The finding this record names, in patient cartilage.

- name: Zone-Dependent Cell Death Markers
  description: >-
    TUNEL and RIP3 positivity concentrate in the middle zone while frank
    necrotic ultrastructure sits in the deep zone - the histological basis for
    this entry treating chondrocyte death as mixed-mode and zone-sorted rather
    than uniform.
  finding_term:
    preferred_term: middle-zone TUNEL and RIP3 positivity with deep-zone necrosis
  notes: >-
    Unbound for the same reason as the record above: this is a post-composition of two
    immunostain readouts and an ultrastructural finding across two cartilage zones, and
    NCIT has no single term for it.
  evidence:
  - reference: PMID:30680829
    reference_title: "Death of chondrocytes in Kashin-Beck disease: Apoptosis, necrosis or necroptosis?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The per cent of TUNEL-positive and RIP3-positive chondrocytes were higher in the middle zones of KBD samples"
    explanation: The zonal distribution of the death markers.
  - reference: PMID:30680829
    reference_title: "Death of chondrocytes in Kashin-Beck disease: Apoptosis, necrosis or necroptosis?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Ultrastructural analysis of chondrocyte from deep cartilage revealed abnormal cells with numerous morphological changes, such as plasma membrane breakdown, generalized swelling of the cytoplasm and loss of identifiable organelles."
    explanation: >-
      The deep-zone ultrastructure, which is a different picture from the middle
      zone. The cached full text places the transmission electron microscopy in
      cartilage from affected children (Figure 5), not in the rat arm.

- name: Absent Vascularisation of the Phalangeal Cartilage End Plate
  description: >-
    In supernumerary fingers removed from affected children and in
    intra-articular bodies from advanced cases, the proximal cartilage end plate
    of the phalanx carries no vascularisation, and epiphyseal bone formation
    around it is altered.
  finding_term:
    preferred_term: unvascularised proximal cartilage end plate of the phalanx
  notes: >-
    Unbound: NCIT's Morphologic Finding branch has no term for absent vascularisation of
    a named cartilage structure.
  evidence:
  - reference: PMID:11482529
    reference_title: "Histology of Kashin-Beck lesions."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The prevailing characteristic of the samples is the absence of vascularisation within the proximal cartilage end plate of the phalanx associated with an alteration of the epiphyseal bone formation."
    explanation: >-
      The finding this record names, and the observation behind the
      angiogenesis-failure reading discussed under `kbd_vascular_direction`.

environmental:
- name: Habitual consumption of grain contaminated with Fusarium T-2 trichothecene mycotoxin
  description: >-
    Grain grown and stored in endemic highland areas carries T-2 toxin from
    Fusarium species. The toxin is directly chondrotoxic, and replacing the
    grain supply is the single most effective preventive measure tested - which
    is the strongest practical argument that this exposure is doing real causal
    work rather than travelling with something else.
  exposure_term:
    preferred_term: dietary exposure to Fusarium T-2 trichothecene mycotoxin in stored grain
    term:
      id: ECTO:0000524
      label: exposure to mycotoxin
  exposure_classifications:
    hazard_agent_type:
    - classification_value: BIOLOGICAL
      notes: >-
        Classified biological because the agent is a fungal secondary
        metabolite, on the same reasoning that makes `Byssinosis` BIOLOGICAL for
        bacterial endotoxin, rather than CHEMICAL as for the mineral-dust
        entries.
    exposure_route:
    - classification_value: ORAL
    exposure_duration:
    - classification_value: CHRONIC
    exposome_domain:
    - classification_value: SPECIFIC_EXTERNAL
  influences_mechanisms:
  - target: Dietary T-2 Toxin Exposure
    environmental_effect: TRIGGERS
    causal_link_type: DIRECT
    description: >-
      Ingested T-2 toxin is the exposure this initiating node describes.
    evidence:
    - reference: PMID:42103195
      reference_title: "Deferoxamine alleviates T-2 toxin-induced articular chondrocyte ferroptosis via the Nrf2/xCT/GPX4 axis: Implications for Kashin-Beck disease pathology."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "T-2 toxin exposure induced severe articular cartilage degradation, accompanied by intracellular iron overload lipid peroxidation, oxidative stress and distinctive mitochondrial damage characteristic of ferroptosis."
      explanation: The controlled demonstration that the toxin alone damages articular cartilage.
  notes: >-
    No IARC group is recorded: IARC has not classified T-2 toxin in a group this
    entry would be entitled to assert, and Kashin-Beck disease is not a
    neoplastic outcome.
  evidence:
  - reference: PMID:35304334
    reference_title: "Animal models of Kashin-Beck disease exposed to environmental risk factors: Methods and comparisons."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Gradually, four etiological hypotheses have been formed, including water of organic poisoning hypothesis represented by fulvic acid (FA), biogeochemical hypothesis represented by selenium (Se) deficiency, food mycotoxin poisoning hypothesis represented by T-2 toxin poisoning and compound etiology theory hypothesis."
    explanation: Names the food mycotoxin hypothesis and its representative agent.
  - reference: PMID:41272335
    reference_title: "Investigation of Selenium and T-2 Toxin Exposure Levels in the Internal and External Environments of Key Areas of Kashin Beck Disease in China."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Although Kashin-Beck disease (KBD) in China has been effectively controlled through comprehensive measures such as selenium supplementation and grain replacement, the underlying environmental risk factors may still persist."
    explanation: >-
      Establishes that the exposure is monitored as a live risk rather than a
      historical one, which is why it is curated as a current exposure. Graded
      OTHER for consistency with the other background sentences quoted here.

- name: Residence on selenium-poor soil with correspondingly low dietary selenium
  description: >-
    Endemic areas sit on soils low in selenium, and the population eats what
    grows there. This is an exposure by absence, which is why it is curated
    separately from the mycotoxin rather than folded into a single "endemic
    diet" entry - the interventions that address it, selenium salt and
    supplementation, are different interventions.
  exposure_term:
    preferred_term: low dietary selenium intake from selenium-poor soil
  exposure_classifications:
    hazard_agent_type:
    - classification_value: CHEMICAL
      notes: >-
        Recorded CHEMICAL because the agent is an element, though the hazard is
        its absence rather than its presence - a case the vocabulary does not
        distinguish.
    exposure_route:
    - classification_value: ORAL
    exposure_duration:
    - classification_value: CHRONIC
    exposome_domain:
    - classification_value: GENERAL_EXTERNAL
      notes: >-
        Recorded GENERAL_EXTERNAL rather than SPECIFIC_EXTERNAL because the
        determinant is the regional geochemistry of the food supply, not a
        discrete personal exposure.
  influences_mechanisms:
  - target: Chronic Dietary Selenium Deficiency
    environmental_effect: PREDISPOSES
    causal_link_type: DIRECT
    description: >-
      Recorded PREDISPOSES rather than TRIGGERS: low selenium sets the
      susceptible state, and the best-characterised animal model needs the toxin
      on top of it to produce the deep-zone lesion that resembles the human
      disease.
    evidence:
    - reference: PMID:22258458
      reference_title: "Histopathology of chondronecrosis development in knee articular cartilage in a rat model of Kashin-Beck disease using T-2 toxin and selenium deficiency conditions."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Chondronecrosis in deep zone of articular cartilage of knee joints was seen in both the low and high T-2 toxin plus selenium-deficient diet groups, these chondronecrotic lesions being very similar to chondronecrosis observed in human KBD."
      explanation: >-
        The lesion that matches human cartilage appears only in the groups given
        both the toxin and the selenium-deficient diet, which is the evidence
        for the predisposing rather than triggering role.
  notes: >-
    `exposure_term` is left unbound. ECTO was searched for a selenium-deficiency
    exposure and has none: `ECTO:0900038` (exposure to selenium via ingestion),
    `ECTO:9000950` (exposure to selenium) and `ECTO:9000192` (exposure to
    selenium ion) all denote the presence of the element, which is the opposite
    of the exposure here. ECTO does carry the pattern this needs elsewhere -
    `ECTO:0400019` is "exposure to decreased protein in food" - so an
    "exposure to decreased selenium in food" term is the natural new-term
    request, and that template is recorded here so the next curator does not
    have to rediscover it. A wrong binding would be worse than none.
  evidence:
  - reference: PMID:35304334
    reference_title: "Animal models of Kashin-Beck disease exposed to environmental risk factors: Methods and comparisons."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Gradually, four etiological hypotheses have been formed, including water of organic poisoning hypothesis represented by fulvic acid (FA), biogeochemical hypothesis represented by selenium (Se) deficiency, food mycotoxin poisoning hypothesis represented by T-2 toxin poisoning and compound etiology theory hypothesis."
    explanation: Names the biogeochemical selenium-deficiency hypothesis.
  - reference: PMID:41272335
    reference_title: "Investigation of Selenium and T-2 Toxin Exposure Levels in the Internal and External Environments of Key Areas of Kashin Beck Disease in China."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The results showed that the average soil selenium content in both endemic and non-endemic villages across the six provinces was below 0.2 mg/kg."
    explanation: >-
      Curated because it complicates the exposure rather than confirming it:
      soil selenium was low in endemic *and* non-endemic villages alike, so
      soil selenium by itself does not mark out where the disease occurs.

- name: Residence in an iodine-deficient highland area
  description: >-
    In the Tibetan endemic area iodine deficiency is severe and near-universal,
    and it is the deficiency that survives multivariate adjustment against the
    disease where serum selenium does not. Curated as a separate exposure
    because it has its own intervention - iodised oil - with its own measured
    effect on growth.
  exposure_term:
    preferred_term: low dietary iodine intake in an iodine-deficient highland area
  exposure_classifications:
    hazard_agent_type:
    - classification_value: CHEMICAL
      notes: >-
        Recorded CHEMICAL on the same reasoning as the selenium entry: the agent
        is an element and the hazard is its absence.
    exposure_route:
    - classification_value: ORAL
    exposure_duration:
    - classification_value: CHRONIC
    exposome_domain:
    - classification_value: GENERAL_EXTERNAL
  influences_mechanisms:
  - target: Iodine Deficiency and Hypothyroidism
    environmental_effect: PREDISPOSES
    causal_link_type: DIRECT
    description: >-
      The dietary exposure behind the biochemical state this node records.
    evidence:
    - reference: PMID:9770558
      reference_title: "Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "When age and sex were controlled for in a multivariate analysis, low urinary iodine, high serum thyrotropin, and low serum thyroxine-binding globulin values were associated with an increased risk of Kashin-Beck disease, but a low serum selenium concentration was not."
      explanation: >-
        Low urinary iodine as an independently associated exposure, with the
        thyroid markers that go with it.
  notes: >-
    `exposure_term` is unbound for the same reason as the selenium entry:
    `ECTO:9000084` is "exposure to iodine", which denotes the presence of the
    element rather than its absence, and no decreased-iodine term exists.
  evidence:
  - reference: PMID:9770558
    reference_title: "Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In areas where severe selenium deficiency is endemic, iodine deficiency is a risk factor for Kashin-Beck disease."
    explanation: The study's conclusion naming iodine deficiency as a risk factor for the disease.
  - reference: PMID:11482536
    reference_title: "Kashin-Beck disease: from etiology to prevention or from prevention to etiology?"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Four factors have been convincingly associated with the disease: selenium deficiency, iodine deficiency, grain contamination with mycotoxin-producing fungi, and water pollution with organic material and fulvic acid."
    explanation: Lists iodine deficiency among the four convincingly associated factors.

- name: Fluoride exposure modifying T-2 toxin detoxification
  description: >-
    Fluoride suppresses carboxylesterase 1, the enzyme that hydrolyses T-2 toxin
    to its less toxic metabolites. Where fluoride exposure is high, the same
    dietary toxin dose reaches chondrocytes in its most toxic form. Curated as a
    modifying exposure rather than an initiating one: nothing here says fluoride
    alone causes the disease.
  exposure_term:
    preferred_term: exposure to fluoride
    term:
      id: ECTO:9000423
      label: exposure to fluoride
  exposure_classifications:
    hazard_agent_type:
    - classification_value: CHEMICAL
    exposure_route:
    - classification_value: ORAL
    exposure_duration:
    - classification_value: CHRONIC
    exposome_domain:
    - classification_value: SPECIFIC_EXTERNAL
  influences_mechanisms:
  - target: Dietary T-2 Toxin Exposure
    environmental_effect: EXACERBATES
    causal_link_type: DIRECT
    description: >-
      Acts on the toxin exposure node by blocking its detoxification rather than
      by adding to the dose.
    evidence:
    - reference: PMID:35990316
      reference_title: "Fluorine impairs carboxylesterase 1-mediated hydrolysis of T-2 toxin and increases its chondrocyte toxicity."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "We identified that recombinant human CES1 was involved in T-2 toxin hydrolysis to generate HT-2 toxin, but not NEO, and NaF repressed the formation of HT-2 toxin."
      explanation: >-
        The biochemical result: recombinant CES1 hydrolyses the toxin and sodium
        fluoride represses that hydrolysis.
  evidence:
  - reference: PMID:35990316
    reference_title: "Fluorine impairs carboxylesterase 1-mediated hydrolysis of T-2 toxin and increases its chondrocyte toxicity."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "This study reveals that CES1 is responsible for the hydrolysis of T-2 toxin, and that fluoride impairs CES1-mediated T-2 toxin detoxification to increase its chondrocyte toxicity."
    explanation: >-
      The authors' conclusion across the enzymology and the chondrocyte
      toxicity assays. Graded OTHER as a conclusion drawn across both.

genetic:
- name: SELENOS susceptibility variant
  gene_term:
    preferred_term: SELENOS
    term:
      id: hgnc:30396
      label: SELENOS
  relationship_type: SUSCEPTIBILITY
  variant_origin: GERMLINE
  frequency: pooled allele-model odds ratio 2.47 (1.85-3.29) in the meta-analysis
  notes: >-
    SEPS1 in the older literature. Curated as susceptibility, not causation -
    none of these variants produces the disease outside an endemic area.
  evidence:
  - reference: PMID:33844169
    reference_title: "Meta-analysis of Association Studies of Selenoprotein Gene Polymorphism and Kashin-Beck Disease: an Updated Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We conclude that the DIO2 (rs225014), SEPS1 (-105G>A), and Sep15 (rs5859) gene polymorphism are associated with susceptibility to KBD."
    explanation: The meta-analysis conclusion naming this locus among the three associated ones.
  - reference: PMID:33844169
    reference_title: "Meta-analysis of Association Studies of Selenoprotein Gene Polymorphism and Kashin-Beck Disease: an Updated Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The OR and 95%CI for SEPS1 (-105G>A) were 2.47 (1.85, 3.29), 9.36 (4.58, 19.12), 2.17 (1.53, 3.08), and 8.60 (4.25, 17.38) in the allele, homozygote, dominant, and recessive models, respectively."
    explanation: The pooled effect estimates this record's `frequency` reports.
  - reference: PMID:33844169
    reference_title: "Meta-analysis of Association Studies of Selenoprotein Gene Polymorphism and Kashin-Beck Disease: an Updated Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "There were a total of eight included case-control studies covering 2025 KBD patients and 1962 controls."
    explanation: The size of the pooled sample behind those estimates.

- name: SELENOF susceptibility variant
  gene_term:
    preferred_term: SELENOF
    term:
      id: hgnc:17705
      label: SELENOF
  relationship_type: SUSCEPTIBILITY
  variant_origin: GERMLINE
  frequency: pooled allele-model odds ratio 2.05 (1.06-3.96) in the meta-analysis
  notes: >-
    Sep15 in the older literature. Split into its own record so the three
    associated selenoprotein loci are individually queryable rather than hidden
    behind one gene binding.
  evidence:
  - reference: PMID:33844169
    reference_title: "Meta-analysis of Association Studies of Selenoprotein Gene Polymorphism and Kashin-Beck Disease: an Updated Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We conclude that the DIO2 (rs225014), SEPS1 (-105G>A), and Sep15 (rs5859) gene polymorphism are associated with susceptibility to KBD."
    explanation: The meta-analysis conclusion naming this locus among the three associated ones.
  - reference: PMID:33844169
    reference_title: "Meta-analysis of Association Studies of Selenoprotein Gene Polymorphism and Kashin-Beck Disease: an Updated Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In addition, the OR and 95%CI for Sep15 (rs5859) were 2.05 (1.06, 3.96) in the allele model."
    explanation: >-
      The pooled estimate, and the one with the widest interval of the three -
      it only just clears 1.

- name: DIO2 variant
  gene_term:
    preferred_term: DIO2
    term:
      id: hgnc:2884
      label: DIO2
  relationship_type: PROTECTIVE
  variant_origin: GERMLINE
  frequency: pooled allele-model odds ratio 0.69 (0.52-0.91) - the association runs in the protective direction
  notes: >-
    Recorded PROTECTIVE rather than SUSCEPTIBILITY because the pooled
    association runs below 1, and because DIO2 encodes the deiodinase that activates
    thyroid hormone - which puts it on the iodine arm of the etiology as much as
    the selenium one. A Tibetan replication study found no single-SNP
    association for rs225014, so the effect is not established across
    populations.
  evidence:
  - reference: PMID:33844169
    reference_title: "Meta-analysis of Association Studies of Selenoprotein Gene Polymorphism and Kashin-Beck Disease: an Updated Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We conclude that the DIO2 (rs225014), SEPS1 (-105G>A), and Sep15 (rs5859) gene polymorphism are associated with susceptibility to KBD."
    explanation: >-
      The meta-analysis conclusion naming this locus among the three associated ones.
      Read with the numbers, not the wording: the sentence says "susceptibility" for all
      three loci together, while all three of its pooled DIO2 estimates run below 1. This
      record follows the estimates, which is why it is PROTECTIVE rather than
      SUSCEPTIBILITY.
  - reference: PMID:33844169
    reference_title: "Meta-analysis of Association Studies of Selenoprotein Gene Polymorphism and Kashin-Beck Disease: an Updated Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Meta-analysis results show that the pooled odds ratios (OR) and 95% confidence intervals (CI) for DIO2 (rs225014) were 0.69 (0.52, 0.91), 0.69 (0.50, 0.96), and 0.72 (0.52, 0.99) in the allele, heterozygote, and dominant models, respectively."
    explanation: >-
      The pooled estimates, all three below 1, which is what makes this record
      PROTECTIVE rather than SUSCEPTIBILITY.
  - reference: PMID:24058403
    reference_title: "Association study of polymorphisms in selenoprotein genes and Kashin-Beck disease and serum selenium/iodine concentration in a Tibetan population."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "In this study, we showed that single SNPs in the genes GPX1 (rs1050450, rs1800668 and rs3811699), TrxR2 (rs5748469), and DIO2 (rs225014) may not be significantly associated with KBD in a Tibetan population."
    explanation: >-
      The replication failure in a Tibetan population, which is why this record
      says the effect is not established rather than reporting the pooled
      estimate alone.
  - reference: PMID:25072641
    reference_title: "Gene expression analysis suggests bone development-related genes GDF5 and DIO2 are involved in the development of Kashin-Beck disease in children rather than adults."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "In addition, bone development-related genes GDF5 (expression ratio = 2.14±0.02) and DIO2 (expression ratio = 0.11±0.05) may contribute to the development of KBD in children rather than in adults."
    explanation: >-
      Graded INDIRECT: an expression difference in patient blood cells is not an
      allelic association, but it is independent evidence that this gene is
      involved, and it is specific to affected children.

- name: ADAM12 susceptibility variants
  gene_term:
    preferred_term: ADAM12
    term:
      id: hgnc:190
      label: ADAM12
  relationship_type: SUSCEPTIBILITY
  variant_origin: GERMLINE
  frequency: rs1278300 reached p = 9.25e-9 in the discovery scan and replicated at p = 0.007
  notes: >-
    ADAM12 is a matrix metalloproteinase-family gene, not a selenoprotein, and
    it carries the strongest single association curated in this entry. It is
    recorded here because an earlier draft of this entry claimed that
    susceptibility maps to selenoprotein genes rather than to cartilage
    structural genes; that claim was drawn from a meta-analysis whose search
    strategy was the two terms "selenoprotein" and "Kashin-Beck disease", so it
    could not have found a cartilage gene had one existed. This is the
    counterexample.
  evidence:
  - reference: PMID:27545300
    reference_title: "A bivariate genome-wide association study identifies ADAM12 as a novel susceptibility gene for Kashin-Beck disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In the BGWAS, ADAM12 gene achieved the most significant association (rs1278300 p-value = 9.25 × 10(-9)) with the KBD."
    explanation: The discovery association from a two-stage bivariate genome-wide scan in 2,417 subjects.
  - reference: PMID:27545300
    reference_title: "A bivariate genome-wide association study identifies ADAM12 as a novel susceptibility gene for Kashin-Beck disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Immunohistochemistry revealed significantly decreased expression level of ADAM12 protein in the KBD articular cartilage (average positive chondrocyte rate = 47.59 ± 7.79%) compared to healthy articular cartilage (average positive chondrocyte rate = 64.73 ± 5.05%)."
    explanation: >-
      The protein-level follow-up in patient cartilage, which is what makes this
      a mechanistic lead rather than a bare association signal.
  - reference: PMID:33844169
    reference_title: "Meta-analysis of Association Studies of Selenoprotein Gene Polymorphism and Kashin-Beck Disease: an Updated Systematic Review."
    supports: NO_EVIDENCE
    evidence_source: HUMAN_CLINICAL
    snippet: "PubMed, Google Scholar, Cochrane library, and Chinese National Knowledge Infrastructure (CNKI) were electronically searched using the terms \"selenoprotein\" and \"Kashin-Beck disease\" or \"KBD\" with a search time from the establishment of the database to January 2021."
    explanation: >-
      Graded NO_EVIDENCE and curated here on purpose: the selenoprotein
      meta-analysis searched on the two terms "selenoprotein" and "Kashin-Beck
      disease", so it bears on this gene not at all and could not have found it.
      That is the reason the retracted claim about selenoprotein genes versus
      cartilage genes was never supportable from it.

- name: Selenoprotein loci tested and not associated
  gene_term:
    preferred_term: GPX1
    term:
      id: hgnc:4553
      label: GPX1
  relationship_type: DISPUTED
  variant_origin: GERMLINE
  notes: >-
    A negative record, kept on purpose, and recorded DISPUTED because that is
    the only value in the vocabulary that does not assert an association. GPX1,
    GPX4, SEPP1 and TrxR2 are exactly
    the selenoproteins a reader would expect to be implicated in a
    selenium-deficiency disease, and the meta-analysis found none of them
    associated. `gene_term` carries GPX1 as the representative locus; the others
    are named in the quoted result.
  evidence:
  - reference: PMID:33844169
    reference_title: "Meta-analysis of Association Studies of Selenoprotein Gene Polymorphism and Kashin-Beck Disease: an Updated Systematic Review."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "For GPX1 (rs1050450, rs1800668, rs3811699), DIO2 (rs225014, rs1352815, rs1388382), TrxR2 (rs1139793, rs5746841), GPX4 (rs713041, rs4807542), and SEPP1 (rs7579, 25191g/a), there was no significant statistical difference between the KBD and control groups (P>0.05)."
    explanation: >-
      Graded REFUTE against this record's own claim, which is the claim that
      these loci confer susceptibility. The meta-analysis tested them and found
      no difference between cases and controls.
  - reference: PMID:24058403
    reference_title: "Association study of polymorphisms in selenoprotein genes and Kashin-Beck disease and serum selenium/iodine concentration in a Tibetan population."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "In this study, we showed that single SNPs in the genes GPX1 (rs1050450, rs1800668 and rs3811699), TrxR2 (rs5748469), and DIO2 (rs225014) may not be significantly associated with KBD in a Tibetan population."
    explanation: The same negative result in an independent Tibetan population.

diagnosis:
- name: Hand Radiography in Children
  description: >-
    Hand radiography is the primary screening measure in endemic areas, and its
    weak point is specificity: a large survey of 3,193 children found several
    normal-variant and developmental signs that are read as positive, the
    commonest being closure reaction of the metaphysis-epiphysis at 14%.
  evidence:
  - reference: PMID:29459762
    reference_title: "The characteristics of positive and confusing hand X-ray signs in diagnosing Kashin-Beck Disease in children in China."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "When screening for Kashin-Beck disease (KBD) in children, hand X-ray examination is the most important measure."
    explanation: States the role of hand radiography in screening, which is what this record describes.
  - reference: PMID:29459762
    reference_title: "The characteristics of positive and confusing hand X-ray signs in diagnosing Kashin-Beck Disease in children in China."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "However, there is high rate of misdiagnosis because of confusing X-ray signs."
    explanation: The misdiagnosis problem this record records as the method's limitation.
  - reference: PMID:29459762
    reference_title: "The characteristics of positive and confusing hand X-ray signs in diagnosing Kashin-Beck Disease in children in China."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The confusing X-ray signs included closure reaction of metaphysis-epiphysis (CRME, 14.28%), thumb variation (0.22%), little finger variation (8.89%), the second metacarpal-phalangeal variation (0.13%) and cystic change (3.85%)."
    explanation: The specific confusing signs and their frequencies in the surveyed children.
  - reference: PMID:29459762
    reference_title: "The characteristics of positive and confusing hand X-ray signs in diagnosing Kashin-Beck Disease in children in China."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Images from 3,193 children were valid."
    explanation: The size of the screened population those frequencies are drawn from.

- name: Radiographic Grading of the Adult Ankle
  description: >-
    In adults the ankle is graded radiographically against the Kellgren-Lawrence
    scale used for primary osteoarthritis. The grading correlates well with
    ankle pain and only weakly with the clinical finger grading, so the two
    scales are not interchangeable.
  evidence:
  - reference: PMID:41342918
    reference_title: "Study on radiographic grading of ankle joint in adult patients with Kashin-Beck disease in Shaanxi and Gansu Province, China."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The study involved 160 adult KBD patients (a total of 320 ankles) as the case group and 170 matched healthy subjects (a total of 340 ankles) as the control group."
    explanation: The case-control design behind the ankle grading scheme.
  - reference: PMID:41342918
    reference_title: "Study on radiographic grading of ankle joint in adult patients with Kashin-Beck disease in Shaanxi and Gansu Province, China."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The X-ray grading of adult KBD ankles was conducted using the Kellgren-Lawrence grading as a reference."
    explanation: >-
      The grading standard, and incidentally the reason the adult disease is
      mistaken for primary osteoarthritis outside endemic areas.
  notes: >-
    The same paper reports that ankle radiographic grade correlates only weakly
    with the clinical grading of the fingers, and that ankle pain and finger
    grading are essentially uncorrelated. That is recorded here rather than in
    the description because it qualifies the method rather than describing it.

- name: National Diagnostic Standard WS/T 207-2010
  description: >-
    China publishes a national diagnostic standard for the disease, and
    contemporary field studies recruit against it rather than against
    study-specific criteria.
  evidence:
  - reference: PMID:39770964
    reference_title: "Kashin-Beck Disease: A Risk Factor for Sarcopenia and Its Interaction with Selenium."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients with KBD were enrolled in the KBD group based on a diagnosis of national criteria WS/T 207-2010."
    explanation: >-
      Names the standard and shows it in use as the recruitment criterion.
  notes: >-
    The standard's own content is not curated here - the text of WS/T 207-2010
    was not obtained, and this record cites only the fact of its use. The
    clinical grading it defines is referred to as degrees I to III in the
    burden and quality-of-life literature quoted elsewhere in this entry.

differential_diagnoses:
- name: Primary Osteoarthritis
  description: >-
    In an adult presenting outside an endemic area, the joint findings are hard
    to separate from primary osteoarthritis - the same radiographic scale
    grades both. The discriminators are the childhood onset, the symmetry, the
    short stature and brachydactyly, and the endemic-area residence history.
  evidence:
  - reference: PMID:41342918
    reference_title: "Study on radiographic grading of ankle joint in adult patients with Kashin-Beck disease in Shaanxi and Gansu Province, China."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "The X-ray grading of adult KBD ankles was conducted using the Kellgren-Lawrence grading as a reference."
    explanation: >-
      Graded INDIRECT: that the standard osteoarthritis scale applies is the
      basis for the confusion, but the sentence does not itself compare the two
      diagnoses.
  - reference: PMID:42000119
    reference_title: "A self-perpetuating cycle of Type H vessel proliferation and T-2 induced inflammation drives KBD pathogenesis."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Kashin-Beck disease (KBD) primarily impairs the epiphyseal plate in children and adolescents, resulting in enlarged bone ends and short stature."
    explanation: >-
      The discriminating half: a growth-plate disease of childhood, which
      primary osteoarthritis is not.

- name: Normal Metaphyseal-Epiphyseal Variants on Hand Radiography
  description: >-
    The practical differential in children is not another disease but normal
    variation. Closure reaction of the metaphysis-epiphysis, little-finger and
    thumb variation, and cystic change are all read as positive for the disease
    in population screening, and the commonest of them occurs in one child in
    seven.
  evidence:
  - reference: PMID:29459762
    reference_title: "The characteristics of positive and confusing hand X-ray signs in diagnosing Kashin-Beck Disease in children in China."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The confusing X-ray signs included closure reaction of metaphysis-epiphysis (CRME, 14.28%), thumb variation (0.22%), little finger variation (8.89%), the second metacarpal-phalangeal variation (0.13%) and cystic change (3.85%)."
    explanation: The confusing signs and their frequencies, from a survey of 3,193 children.
  - reference: PMID:29459762
    reference_title: "The characteristics of positive and confusing hand X-ray signs in diagnosing Kashin-Beck Disease in children in China."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "However, there is high rate of misdiagnosis because of confusing X-ray signs."
    explanation: Why they matter - they are the stated cause of the high misdiagnosis rate.

treatments:
- name: Grain Replacement
  description: >-
    Replacing the locally grown, mycotoxin-contaminated staple grain with grain
    from outside the endemic area. Tied with comprehensive multi-component
    programmes as the most effective primary prevention tested, at a pooled odds
    ratio of 0.15 for new incidence in healthy children.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: replacement of the contaminated staple grain supply
    term:
      id: NCIT:C15843
      label: Preventive Intervention
  target_mechanisms:
  - target: Dietary T-2 Toxin Exposure
    description: >-
      Acts on the toxin exposure directly by removing the contaminated food
      source.
  notes: >-
    `therapeutic_modality: BEHAVIORAL` deliberately, where `Drinking Water Improvement`
    below is `OTHER`: the enum's `BEHAVIORAL` description explicitly covers dietary
    intervention, and what the household eats changes here. Replacing a village water
    supply changes nothing about what anyone does.
  evidence:
  - reference: PMID:31490368
    reference_title: "Prevention and control strategies for children Kashin-Beck disease in China: A systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The pooled odds ratios (ORs) and confidence intervals (95% CIs) for primary prevention new incidence in healthy children following interventions to comprehensive measures, change of grain, salt-rich selenium, and improvements of water were 0.15 (0.02, 0.95), 0.15 (0.03, 0.70), 0.19 (0.09, 0.38), and 0.20 (0.09, 0.42), respectively."
    explanation: >-
      The pooled effect estimates for all four interventions in one sentence -
      grain change at OR 0.15 for new incidence.
  - reference: PMID:31490368
    reference_title: "Prevention and control strategies for children Kashin-Beck disease in China: A systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Comprehensive measures and change of grain were the most effective measures in preventing new case, whereas improvement of water and salt-rich selenium resulted in clinical improvements in children KBD."
    explanation: >-
      The meta-analysis' own ranking, and the useful distinction it draws:
      grain change prevents new cases, while water and selenium improve
      existing ones.

- name: Selenium Supplementation
  description: >-
    Selenium-enriched salt and other selenium supplementation. The evidence
    pulls in two directions and both halves are curated here: two meta-analyses
    find it prevents new cases and improves radiographic structure in children,
    while the one randomised trial done in Tibet found it did nothing for
    established disease, growth or thyroid function once iodine deficiency was
    corrected. That last result is a real constraint on reading selenium
    deficiency as the whole story.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: selenium supplementation
    term:
      id: NCIT:C15433
      label: Nutritional Support
    therapeutic_agent:
    - preferred_term: selenium
      term:
        id: CHEBI:27568
        label: selenium atom
  target_mechanisms:
  - target: Selenoenzyme Antioxidant Capacity Deficit
    description: >-
      Restoring selenium restores the substrate for selenoprotein synthesis,
      which is the node this treatment targets.
  evidence:
  - reference: PMID:31490368
    reference_title: "Prevention and control strategies for children Kashin-Beck disease in China: A systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The pooled odds ratios (ORs) and confidence intervals (95% CIs) for primary prevention new incidence in healthy children following interventions to comprehensive measures, change of grain, salt-rich selenium, and improvements of water were 0.15 (0.02, 0.95), 0.15 (0.03, 0.70), 0.19 (0.09, 0.38), and 0.20 (0.09, 0.42), respectively."
    explanation: The primary-prevention estimate for selenium-rich salt, OR 0.19.
  - reference: PMID:18693119
    reference_title: "Selenium for preventing Kashin-Beck osteoarthropathy in children: a meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The pooled Peto-OR and NNT favoring selenium supplement was 0.13 (95% CI: 0.04-0.47) and 21 in RCTs, and 0.16 (95% CI: 0.09-0.30) and 26 in non-RCTs."
    explanation: >-
      An independent meta-analysis of the preventive effect, with a number
      needed to treat of 21 in the randomised trials.
  - reference: PMID:31376086
    reference_title: "The effectiveness of treatments for Kashin-Beck disease: a systematic review and network meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In children or adolescents, selenium (risk ratio 1.88, 95% confidence interval (CI) 1.51-2.33), vitamin C (2.03, 1.40-2.95) and aspirin (2.14, 1.12-4.08) were effective for radiographic structure improvement."
    explanation: >-
      The network meta-analysis result for radiographic structure improvement in
      children, alongside vitamin C and aspirin.
  - reference: PMID:29511006
    reference_title: "Effects of five types of selenium supplementation for treatment of Kashin-Beck disease in children: a systematic review and network meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "NMAs showed that all five kinds of selenium supplementation had higher metaphysis X-ray improvement which were superior to placebo."
    explanation: >-
      All five formulations beat placebo on metaphyseal X-ray improvement; the
      same review is explicit that the evidence quality is too low to rank them.
  - reference: PMID:12816783
    reference_title: "Selenium and iodine supplementation of rural Tibetan children affected by Kashin-Beck osteoarthropathy."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "However, selenium supplementation had no effect on established Kashin-Beck disease, growth, or thyroid function once iodine deficiency was corrected."
    explanation: >-
      The negative randomised result in established disease, once iodine was
      replaced. Curated as REFUTE against the treatment claim rather than
      omitted, because it is the only individual randomised trial curated here
      - the other treatment references are meta-analyses.

- name: Drinking Water Improvement
  description: >-
    Replacing shallow-well water with a cleaner supply. It works - and it is the
    intervention the food-borne hypotheses do not predict, which is why the
    water-organic-poisoning hypothesis is curated as ALTERNATIVE rather than
    retired.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: improvement of the drinking water supply
    term:
      id: NCIT:C15843
      label: Preventive Intervention
  target_mechanisms:
  - target: Fulvic Acid Free-Radical Generation in Cartilage
    description: >-
      Curated against the fulvic-acid node, which is the mechanism the
      intervention is supposed to interrupt. The link is hypothesised rather
      than demonstrated: replacing a water supply changes more than its organic
      content.
  evidence:
  - reference: PMID:31490368
    reference_title: "Prevention and control strategies for children Kashin-Beck disease in China: A systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The pooled odds ratios (ORs) and confidence intervals (95% CIs) for primary prevention new incidence in healthy children following interventions to comprehensive measures, change of grain, salt-rich selenium, and improvements of water were 0.15 (0.02, 0.95), 0.15 (0.03, 0.70), 0.19 (0.09, 0.38), and 0.20 (0.09, 0.42), respectively."
    explanation: The primary-prevention estimate for water improvement, OR 0.20.
  - reference: PMID:31490368
    reference_title: "Prevention and control strategies for children Kashin-Beck disease in China: A systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Comprehensive measures and change of grain were the most effective measures in preventing new case, whereas improvement of water and salt-rich selenium resulted in clinical improvements in children KBD."
    explanation: Places water improvement among the measures that improve existing disease.
  notes: >-
    `therapeutic_modality` is OTHER rather than BEHAVIORAL. Replacing a village
    water supply is public-works engineering; nothing about the patient's
    behaviour changes.

- name: Iodine Replacement
  description: >-
    Iodised oil in the Tibetan endemic area. The one intervention in this entry
    that produced a measured growth response: children who received iodine
    recovered height-for-age, and unsupplemented controls did not.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: iodine supplementation
    term:
      id: NCIT:C15433
      label: Nutritional Support
    therapeutic_agent:
    - preferred_term: iodine
      term:
        id: CHEBI:24859
        label: iodine atom
  target_mechanisms:
  - target: Iodine Deficiency and Hypothyroidism
    description: Corrects the deficiency this node describes.
    evidence:
    - reference: PMID:12816783
      reference_title: "Selenium and iodine supplementation of rural Tibetan children affected by Kashin-Beck osteoarthropathy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Height-for-age z scores increased significantly in the subjects who received placebo and iodine or selenium and iodine. In contrast, unsupplemented control subjects did not recover from growth retardation."
      explanation: >-
        Evidence for the link: every arm that received iodine recovered height-for-age
        and the unsupplemented controls did not, which is the treatment acting on this
        node rather than on the disease as a whole.
  evidence:
  - reference: PMID:12816783
    reference_title: "Selenium and iodine supplementation of rural Tibetan children affected by Kashin-Beck osteoarthropathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Height-for-age z scores increased significantly in the subjects who received placebo and iodine or selenium and iodine. In contrast, unsupplemented control subjects did not recover from growth retardation."
    explanation: >-
      The growth response, and its control arm. Note the trial was not designed
      to test iodine against no iodine - every supplemented arm received it -
      so the comparison is with unsupplemented controls.
  - reference: PMID:9770558
    reference_title: "Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "In areas where severe selenium deficiency is endemic, iodine deficiency is a risk factor for Kashin-Beck disease."
    explanation: >-
      Graded INDIRECT: the observational study establishes the risk factor this
      treatment addresses, not the treatment's effect.

- name: Chondroitin and Glucosamine
  description: >-
    The best-performing symptomatic treatment for adults in the network
    meta-analysis of KBD treatments, on a standardised mean difference of 1.46
    for pain against placebo. An earlier draft of this entry recorded no adult
    treatment at all, which was wrong.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: chondroitin sulfate
      term:
        id: CHEBI:37397
        label: chondroitin sulfate
    - preferred_term: glucosamine
      term:
        id: CHEBI:5417
        label: glucosamine
  target_mechanisms:
  - target: Secondary Degenerative Arthropathy
    treatment_effect: MODULATES
    description: >-
      Symptomatic: it treats the adult arthropathy without acting on any
      upstream node in this graph.
  evidence:
  - reference: PMID:31376086
    reference_title: "The effectiveness of treatments for Kashin-Beck disease: a systematic review and network meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In adults, chondroitin plus glucosamine was the best for pain (standardised mean difference 1.46, 95% CI 1.07-1.85), followed by intra-articular injection of hyaluronic acid (IAH) (1.09, 0.70-1.48), chondroitin (0.84, 0.47-1.21), diclofenac (0.63, 1.18-1.08), naproxen (0.55, 0.12-0.98), meloxicam (0.52, 0.03-1.01) and glucosamine (0.40, 0.13-0.67) compared to placebo"
    explanation: The ranked effect estimates, with this combination at the top.
  - reference: PMID:31376086
    reference_title: "The effectiveness of treatments for Kashin-Beck disease: a systematic review and network meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Chondroitin, glucosamine, IAH and nonsteroid anti-inflammatory drugs are effective for symptom improvements of KBD in adults."
    explanation: The review's own conclusion for adult symptomatic treatment.
  notes: >-
    The same review is explicit that "the strength of most evidence was limited
    by the small number of trials with low to moderate quality", and this record
    should be read with that caveat.

- name: Intra-Articular Hyaluronic Acid
  description: >-
    Ranked second for adult pain in the network meta-analysis, at a standardised
    mean difference of 1.09 against placebo.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: intra-articular hyaluronic acid injection
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: hyaluronic acid
      term:
        id: CHEBI:16336
        label: hyaluronic acid
  target_mechanisms:
  - target: Secondary Degenerative Arthropathy
    treatment_effect: MODULATES
    description: Symptomatic treatment of the adult joint, delivered into the joint itself.
  evidence:
  - reference: PMID:31376086
    reference_title: "The effectiveness of treatments for Kashin-Beck disease: a systematic review and network meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In adults, chondroitin plus glucosamine was the best for pain (standardised mean difference 1.46, 95% CI 1.07-1.85), followed by intra-articular injection of hyaluronic acid (IAH) (1.09, 0.70-1.48), chondroitin (0.84, 0.47-1.21), diclofenac (0.63, 1.18-1.08), naproxen (0.55, 0.12-0.98), meloxicam (0.52, 0.03-1.01) and glucosamine (0.40, 0.13-0.67) compared to placebo"
    explanation: The ranked effect estimates, with intra-articular hyaluronic acid second.

- name: Nonsteroidal Anti-Inflammatory Drugs
  description: >-
    Diclofenac, naproxen and meloxicam all beat placebo for adult pain in the
    network meta-analysis, with smaller effects than the nutraceuticals above.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: nonsteroidal anti-inflammatory drug
      term:
        id: NCIT:C257
        label: Nonsteroidal Antiinflammatory Drug
    - preferred_term: diclofenac
      term:
        id: CHEBI:47381
        label: diclofenac
    - preferred_term: naproxen
      term:
        id: CHEBI:7476
        label: naproxen
    - preferred_term: meloxicam
      term:
        id: CHEBI:6741
        label: meloxicam
  target_mechanisms:
  - target: Secondary Degenerative Arthropathy
    treatment_effect: MODULATES
    description: Symptomatic analgesia for the adult arthropathy.
  evidence:
  - reference: PMID:31376086
    reference_title: "The effectiveness of treatments for Kashin-Beck disease: a systematic review and network meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In adults, chondroitin plus glucosamine was the best for pain (standardised mean difference 1.46, 95% CI 1.07-1.85), followed by intra-articular injection of hyaluronic acid (IAH) (1.09, 0.70-1.48), chondroitin (0.84, 0.47-1.21), diclofenac (0.63, 1.18-1.08), naproxen (0.55, 0.12-0.98), meloxicam (0.52, 0.03-1.01) and glucosamine (0.40, 0.13-0.67) compared to placebo"
    explanation: The three individual agents and their effect estimates against placebo.
  - reference: PMID:31376086
    reference_title: "The effectiveness of treatments for Kashin-Beck disease: a systematic review and network meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Chondroitin, glucosamine, IAH and nonsteroid anti-inflammatory drugs are effective for symptom improvements of KBD in adults."
    explanation: The review's conclusion grouping them with the nutraceuticals as effective for adult symptoms.

- name: Vitamin C and Aspirin for Radiographic Structure in Children
  description: >-
    Both improved radiographic structure in children in the network
    meta-analysis, and the same review says the evidence for both is not
    established. Curated with that contradiction visible rather than resolved.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: vitamin C
      term:
        id: CHEBI:22652
        label: ascorbic acid
    - preferred_term: aspirin
      term:
        id: CHEBI:15365
        label: acetylsalicylic acid
  target_mechanisms:
  - target: Endochondral Ossification Failure at the Growth Plate
    treatment_effect: MODULATES
    description: >-
      Radiographic structure improvement is a readout of the growth-plate
      lesion, which is the node this points at. No mechanism is proposed for
      either agent here.
  evidence:
  - reference: PMID:31376086
    reference_title: "The effectiveness of treatments for Kashin-Beck disease: a systematic review and network meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In children or adolescents, selenium (risk ratio 1.88, 95% confidence interval (CI) 1.51-2.33), vitamin C (2.03, 1.40-2.95) and aspirin (2.14, 1.12-4.08) were effective for radiographic structure improvement."
    explanation: The effect estimates for both agents on radiographic structure in children.
  - reference: PMID:31376086
    reference_title: "The effectiveness of treatments for Kashin-Beck disease: a systematic review and network meta-analysis."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "Evidence of surgical and complementary treatments for symptoms and aspirin and vitamin C for structure has yet to be established."
    explanation: >-
      The same review's key-points list says the efficacy of aspirin and vitamin
      C has not been established. Graded REFUTE against this record's own claim
      and curated alongside the positive estimate, because a reader who saw only
      one of the two sentences would be misled.

- name: Arthrodesis and Reconstructive Surgery of the Damaged Joint
  description: >-
    Surgical salvage of an end-stage joint. The curated case is a conservative
    tibiotalocalcaneal fusion for talar avascular necrosis with ankle and subtalar
    arthritis in a 50-year-old patient, achieving bony union and a plantigrade foot
    at four months. Recorded because a disease whose adult burden is fixed joint
    deformity has a surgical arm, and this entry previously had none.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: tibiotalocalcaneal arthrodesis
    term:
      id: NCIT:C52007
      label: Arthrodesis
  target_mechanisms:
  - target: Secondary Degenerative Arthropathy
    treatment_effect: BYPASSES
    description: >-
      Recorded BYPASSES rather than INHIBITS: fusing the joint removes the painful
      articulation instead of acting on the cartilage degeneration that destroyed it.
    evidence:
    - reference: PMID:31335683
      reference_title: "Conservative tibiotalocalcaneal fusion for partial talar avascular necrosis in conjunction with ankle and subtalar joint osteoarthritis in Kashin-Beck disease: A case report."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Conservative tibiotalocalcaneal fusion could help preserving much more viable talar body, maintaining most structural integrity of the ankle joint, and achieving a stable and plantigrade foot postoperatively."
      explanation: >-
        Evidence for the link itself rather than for the treatment: what the procedure
        is credited with is a stable, plantigrade foot and preserved structural
        integrity, which is the arthropathy being bypassed rather than reversed.
  evidence:
  - reference: PMID:31335683
    reference_title: "Conservative tibiotalocalcaneal fusion for partial talar avascular necrosis in conjunction with ankle and subtalar joint osteoarthritis in Kashin-Beck disease: A case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A conservative tibiotalocalcaneal fusion attempting to preserve as much viable talar body as possible was performed using a humeral locking plate and 2 cannulated compression screws."
    explanation: The procedure this record names, as performed.
  - reference: PMID:31335683
    reference_title: "Conservative tibiotalocalcaneal fusion for partial talar avascular necrosis in conjunction with ankle and subtalar joint osteoarthritis in Kashin-Beck disease: A case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Bone union proved by CT scan and a good alignment of the left limb were achieved at 4-month follow-up postoperatively."
    explanation: The reported outcome, at four months.
  - reference: PMID:31376086
    reference_title: "The effectiveness of treatments for Kashin-Beck disease: a systematic review and network meta-analysis."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "Evidence of surgical and complementary treatments for symptoms and aspirin and vitamin C for structure has yet to be established."
    explanation: >-
      Graded REFUTE against the strength of this record, not against its existence.
      The network meta-analysis of 44 randomised trials says the efficacy of surgical
      treatment for this disease has not been established, so what is curated above is
      a single case report of a technique in use, not evidence that it works.
  notes: >-
    `NCIT:C52007` (Arthrodesis) replaces the `NCIT:C16186` (Orthopedic Surgical
    Procedure) this record first carried. `C52007` sits directly under `C16186` and is
    reachable from `NCIT:C25218`, so it is the more specific term that still accurately
    represents the claim, which is what the ontology contract asks for. NCIT does carry
    `NCIT:C220188` (Tibiotalar Arthrodesis), but that names a tibia-talus fusion and
    the procedure here is tibiotalo*calcaneal* - a different, larger fusion, not a
    narrower case of it - so binding it would be wrong rather than merely specific. The
    full specificity stays in `preferred_term`.

    This is one patient. The evidence base for surgery in this disease is a case
    literature, which is exactly what the network meta-analysis says, and both are
    recorded here rather than only the encouraging half. The case is also unusual on
    its own terms - its authors note talar avascular necrosis is rarely reported in
    this disease - so it should not be read as the typical surgical indication.

- name: Conservative Orthotic Management and Activity Restriction
  description: >-
    Non-operative management of the painful end-stage joint with a rigid orthosis and
    reduced loading. Curated with the result it produced in the one case recorded
    here, which was failure - it is the step that preceded surgery rather than an
    alternative to it.
  therapeutic_modality: DEVICE
  treatment_term:
    preferred_term: rigid orthosis and activity restriction
    term:
      id: NCIT:C15315
      label: Rehabilitation
    qualifiers:
    - predicate:
        preferred_term: medical device
        term:
          id: NCIT:C16830
          label: Medical Device
      value:
        preferred_term: rigid orthosis
        term:
          id: NCIT:C86054
          label: Brace
  target_mechanisms:
  - target: Secondary Degenerative Arthropathy
    treatment_effect: MODULATES
    description: >-
      Aimed at the pain and loading of the degenerate joint; no mechanism upstream of
      it is addressed.
    evidence:
    - reference: PMID:31335683
      reference_title: "Conservative tibiotalocalcaneal fusion for partial talar avascular necrosis in conjunction with ankle and subtalar joint osteoarthritis in Kashin-Beck disease: A case report."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "A 50-year-old woman presented with severe pain and limited range of motion in her left ankle and subtalar joint while walking for 2 years."
      explanation: >-
        Evidence for the link: the pain and restricted range of motion in the
        degenerate ankle and subtalar joint are what the orthosis and activity
        restriction were applied to.
  evidence:
  - reference: PMID:31335683
    reference_title: "Conservative tibiotalocalcaneal fusion for partial talar avascular necrosis in conjunction with ankle and subtalar joint osteoarthritis in Kashin-Beck disease: A case report."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "Conservative treatment with rigid orthosis and activity restriction could not help reduce the pain in the left foot."
    explanation: >-
      Graded REFUTE: in the one case curated here the conservative approach did not
      relieve the pain, which is why the record exists at all. A single case cannot
      establish that orthotic management is generally ineffective, and this record does
      not claim it does.
  - reference: PMID:31335683
    reference_title: "Conservative tibiotalocalcaneal fusion for partial talar avascular necrosis in conjunction with ankle and subtalar joint osteoarthritis in Kashin-Beck disease: A case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A 50-year-old woman presented with severe pain and limited range of motion in her left ankle and subtalar joint while walking for 2 years."
    explanation: The presentation the conservative measures were applied to.
  notes: >-
    `therapeutic_modality: DEVICE` for the orthosis, bound to the closest NCIT clinical
    *action* term (`NCIT:C15315` Rehabilitation) rather than to a device term, per the
    `CLAUDE.md` rule that `TreatmentTerm` is rooted at Clinical Intervention or
    Procedure and cannot take an equipment term. The device concept is kept queryable
    the way that rule prescribes, as a `qualifiers` predicate-value pair with
    `NCIT:C16830` (Medical Device) as the predicate - the same carve-out the cochlear
    implant entries use. NCIT has no term for an orthosis as such; `NCIT:C86054`
    (Brace) is the closest device concept and is what a rigid ankle orthosis is.

prevalence:
- population: China, national surveillance
  measure_type: ANNUAL_INCIDENCE
  prevalence_class: ABOVE_1_IN_1000
  rate_per_100000: 180.0
  rate_denominator: POPULATION_PER_YEAR
  notes: >-
    The 2015 national figure of 0.18%, the end point of a twenty-five-year
    decline from 22.1% in 1990. 0.18% is 180 per 100,000, which is the
    ABOVE_1_IN_1000 band. The source calls this an incidence, and it is recorded
    as one: it is a detection rate among the at-risk population under
    surveillance, so `rate_denominator` is POPULATION_PER_YEAR rather than
    person-years. Any single year is a snapshot of a disease being actively
    eliminated.
  evidence:
  - reference: PMID:31548049
    reference_title: "Endemic Kashin-Beck disease: A food-sourced osteoarthropathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "National incidences were 22.1% in 1990, 16.0% in 1995, 12.3% in 2000, 5.5% in 2005, 0.38% in 2010, and 0.18 in 2015, respectively."
    explanation: The full national series, which is more informative than any one year of it.

- population: Endemic areas of China, 2016
  measure_type: POINT_PREVALENCE
  prevalence_class: ABOVE_1_IN_1000
  rate_per_100000: 2548.0
  rate_denominator: POPULATION
  notes: >-
    574,925 prevalent patients among the 22,567,600 inhabitants of endemic
    areas, which is 2,548 per 100,000 or about 2.5%. The denominator is the
    endemic-area population, not the national one. This is the residual burden
    and it is the point: incidence has collapsed while the people already
    damaged remain.
  evidence:
  - reference: PMID:31548049
    reference_title: "Endemic Kashin-Beck disease: A food-sourced osteoarthropathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Although new patients were annually decreased, it still affected 22,567,600 inhabitants and there were 574,925 patients in 2016."
    explanation: The residual prevalent burden against the at-risk denominator.

clinical_burden:
  burden_level: HIGH
  rationale: >-
    The skeletal deformity is permanent and acquired in childhood, and the
    adult treatment literature is symptomatic throughout - nothing curated here
    modifies the underlying lesion. Measured quality of life is lower than in osteoarthritis on every domain but
    economics; depression is present in half of patients; and the national
    economic burden is quantified. The burden is high on functional impact and
    duration rather than on mortality.
  evidence:
  - reference: PMID:37143055
    reference_title: "Health-related quality of life in patients with Kashin-Beck disease is lower than in those with osteoarthritis: a cross-sectional study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The QOL of KBD patients was significantly lower than that of OA patients and healthy people."
    explanation: The comparison this assessment rests on - worse than osteoarthritis, in the same region.
  - reference: PMID:37143055
    reference_title: "Health-related quality of life in patients with Kashin-Beck disease is lower than in those with osteoarthritis: a cross-sectional study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The average scores for physical functions, activity limitations, support of society, mental health and general health were significantly lower in KBD patients than that in OA patients and healthy people except for economics."
    explanation: The domain-by-domain result, including the one domain that did not differ.
  - reference: PMID:40963707
    reference_title: "Prevalence and Risk Factors of Depression in Patients With Endemic Osteoarthritis Kashin-Beck Disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Depression was present in 53.2% of patients in our KBD samples."
    explanation: The mental-health component of the burden.
  - reference: PMID:38250701
    reference_title: "Disease and Economic Burden of Kashin-Beck Disease - China, 2021‎."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The most substantial reduction in healthy life expectancy was observed among patients with degree II severity and those aged 60 years and older, resulting in a total indirect economic burden of 112.74 million Chinese Yuan (CNY)."
    explanation: >-
      The national economic burden and the demographic where healthy life
      expectancy is lost fastest.
  - reference: PMID:31376086
    reference_title: "The effectiveness of treatments for Kashin-Beck disease: a systematic review and network meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Chondroitin, glucosamine, IAH and nonsteroid anti-inflammatory drugs are effective for symptom improvements of KBD in adults."
    explanation: >-
      The management burden half of the assessment: the treatments with
      established adult efficacy are symptomatic ones.

biochemical:
- name: Serum selenium
  presence: Decreased
  biomarker_term:
    preferred_term: serum selenium concentration
    term:
      id: NCIT:C825
      label: Selenium
  notes: >-
    The marker the biogeochemical hypothesis is named for, and the one whose
    association does not survive adjustment. Both facts are curated here. The specimen
    is not machine-queryable: NCIT was searched and has no specimen-qualified selenium
    concept - `NCIT:C825` (Selenium) is the element, `NCIT:C187825` (Selenium
    Measurement) and `NCIT:C184458` (Dietary Selenium Measurement) name assays rather
    than analytes, and nothing distinguishes serum from hair. The distinction is
    load-bearing here, so it is carried in `preferred_term` and stated in these notes
    rather than left to be inferred.
  readouts:
  - target: Chronic Dietary Selenium Deficiency
    relationship: READOUT_OF
    direction: NEGATIVE
    endpoint_context: DIAGNOSTIC
    interpretation: >-
      Low serum selenium reports the dietary deficiency directly. It does not
      discriminate affected from unaffected residents of the same endemic area.
    evidence:
    - reference: PMID:9770558
      reference_title: "Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Severe selenium deficiency was documented in all villages; 38 percent of subjects had serum concentrations of less than 5 ng per milliliter (64 nmol per liter; normal, 60 to 105 ng per milliliter [762 to 1334 nmol per liter])."
      explanation: >-
        The deficiency measured directly, with the reference interval it is measured
        against - 38% of children below 5 ng/mL against a normal 60-105 ng/mL.
    - reference: PMID:9770558
      reference_title: "Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status."
      supports: REFUTE
      evidence_source: HUMAN_CLINICAL
      snippet: "When age and sex were controlled for in a multivariate analysis, low urinary iodine, high serum thyrotropin, and low serum thyroxine-binding globulin values were associated with an increased risk of Kashin-Beck disease, but a low serum selenium concentration was not."
      explanation: >-
        Graded REFUTE against this marker as a diagnostic readout for the disease
        rather than for the deficiency: in multivariate analysis a low serum selenium
        was *not* associated with the disease, while the iodine and thyroid markers
        were. This is the load-bearing negative behind curating an iodine arm at all.
  reference_ranges:
  - lower_bound: 60.0
    upper_bound: 105.0
    unit: ng/mL
    population: general assay reference interval quoted by the source; not derived from or stratified to the study cohort
    evidence:
    - reference: PMID:9770558
      reference_title: "Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Severe selenium deficiency was documented in all villages; 38 percent of subjects had serum concentrations of less than 5 ng per milliliter (64 nmol per liter; normal, 60 to 105 ng per milliliter [762 to 1334 nmol per liter])."
      explanation: >-
        The interval is quoted verbatim in the same sentence as the deficiency
        measurement - "normal, 60 to 105 ng per milliliter".
    notes: >-
      `loinc_term` is absent: no LOINC lookup was performed for this analyte, and
      the slot is `recommended` rather than required. The bounds and unit are taken
      from the cited sentence, not from a laboratory manual. `population` says what
      this interval is and is not: the source quotes it as the assay's normal range to
      measure its subjects against, so it is not a Tibetan-children-specific interval
      and must not be read as one, even though the study that quotes it measured
      children aged 5 to 15 in rural Tibet.
  evidence:
  - reference: PMID:9770558
    reference_title: "Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Severe selenium deficiency was documented in all villages; 38 percent of subjects had serum concentrations of less than 5 ng per milliliter (64 nmol per liter; normal, 60 to 105 ng per milliliter [762 to 1334 nmol per liter])."
    explanation: The measurement, its threshold, and the reference range.

- name: Hair selenium
  presence: Decreased
  biomarker_term:
    preferred_term: hair selenium concentration
    term:
      id: NCIT:C825
      label: Selenium
  notes: >-
    Recorded separately from serum selenium because it is a different specimen with a
    different time constant - hair integrates months of intake - and because it is the
    marker current Chinese surveillance actually uses for population monitoring. Both
    records bind `NCIT:C825` because NCIT has no specimen-qualified selenium term; see
    the note on the serum record for the search.
  readouts:
  - target: Chronic Dietary Selenium Deficiency
    relationship: READOUT_OF
    direction: NEGATIVE
    endpoint_context: MONITORING
    interpretation: >-
      Used to monitor whether the exposure is returning in areas where the disease was
      controlled. Note it separated endemic from non-endemic villages in only one of
      six provinces surveyed.
    evidence:
    - reference: PMID:41272335
      reference_title: "Investigation of Selenium and T-2 Toxin Exposure Levels in the Internal and External Environments of Key Areas of Kashin Beck Disease in China."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "To dynamically assess the selenium exposure levels in humans (using children’s hair selenium as a biomarker) and the selenium status in the external environment (soil selenium and grain selenium) in historical severe endemic areas and adjacent non-endemic areas in China"
      explanation: >-
        States the surveillance use this readout records - children's hair selenium as
        the human exposure biomarker.
    - reference: PMID:41272335
      reference_title: "Investigation of Selenium and T-2 Toxin Exposure Levels in the Internal and External Environments of Key Areas of Kashin Beck Disease in China."
      supports: SUPPORT
      directness: INDIRECT
      evidence_source: HUMAN_CLINICAL
      snippet: "The overall selenium status in children was at a moderate level; however, hair selenium levels in endemic villages of Sichuan were significantly lower than those in non-endemic villages."
      explanation: >-
        Graded INDIRECT and curated for what it complicates: hair selenium was lower in
        endemic than non-endemic villages in Sichuan alone, so it tracks the exposure
        without cleanly marking out where the disease occurs.
  evidence:
  - reference: PMID:41272335
    reference_title: "Investigation of Selenium and T-2 Toxin Exposure Levels in the Internal and External Environments of Key Areas of Kashin Beck Disease in China."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Particularly in Tibet and Sichuan, grain selenium levels remain critically low"
    explanation: >-
      The dietary source the hair measurement integrates - grain selenium still
      critically low in Tibet and Sichuan.

- name: Urinary iodine
  presence: Decreased
  biomarker_term:
    preferred_term: urinary iodine concentration
    term:
      id: NCIT:C594
      label: Iodine
  notes: >-
    The one biochemical marker in this entry that survived multivariate adjustment
    against the disease. Curated because that result, not the selenium result, is what
    the iodine arm of the etiology rests on.
  readouts:
  - target: Iodine Deficiency and Hypothyroidism
    relationship: READOUT_OF
    direction: NEGATIVE
    endpoint_context: DIAGNOSTIC
    interpretation: >-
      Low urinary iodine reports the deficiency and, unlike serum selenium, remained
      associated with the disease after adjustment for age and sex.
    evidence:
    - reference: PMID:9770558
      reference_title: "Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "When age and sex were controlled for in a multivariate analysis, low urinary iodine, high serum thyrotropin, and low serum thyroxine-binding globulin values were associated with an increased risk of Kashin-Beck disease, but a low serum selenium concentration was not."
      explanation: The multivariate result this readout rests on.
    - reference: PMID:9770558
      reference_title: "Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "hypothyroidism was more frequent (23 percent vs. 4 percent, P=0.01)."
      explanation: >-
        The clinical consequence measured alongside it - hypothyroidism nearly six
        times as frequent in affected children as in controls.
  reference_ranges:
  - lower_bound: 5.0
    upper_bound: 25.0
    unit: ug/dL
    population: general assay reference interval quoted by the source; not derived from or stratified to the study cohort
    evidence:
    - reference: PMID:9770558
      reference_title: "Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Of the 557 subjects in whom urinary iodine was measured, 66 percent had a urinary iodine concentration of less than 2 microg per deciliter (157 nmol per liter; normal, 5 to 25 microg per deciliter [394 to 1968 nmol per liter])."
      explanation: >-
        The interval is quoted verbatim in the same sentence as the deficiency
        measurement - "normal, 5 to 25 microg per deciliter".
    notes: >-
      Unit recorded in UCUM notation as `ug/dL`; the source writes it "microg per
      deciliter". `loinc_term` is absent for the same reason as the serum selenium
      range - no LOINC lookup was performed and the slot is `recommended`. As there,
      `population` records that this is the assay's general normal range quoted by the
      source, not an interval derived from the Tibetan cohort it was applied to.
  evidence:
  - reference: PMID:9770558
    reference_title: "Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Of the 557 subjects in whom urinary iodine was measured, 66 percent had a urinary iodine concentration of less than 2 microg per deciliter (157 nmol per liter; normal, 5 to 25 microg per deciliter [394 to 1968 nmol per liter])."
    explanation: >-
      The population distribution and the reference interval - two thirds of children
      below 2 microg/dL against a normal 5-25.

- name: Serum thyrotropin
  presence: Increased
  biomarker_term:
    preferred_term: serum thyroid-stimulating hormone
    term:
      id: NCIT:C2280
      label: Thyroid-Stimulating Hormone
  notes: >-
    Raised thyrotropin is the functional consequence of the iodine deficiency above,
    and is curated as its own marker because it, and not the iodine level alone, is
    what the multivariate model retained.
  readouts:
  - target: Iodine Deficiency and Hypothyroidism
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: >-
      High serum thyrotropin reports the hypothyroid state this node describes and was
      independently associated with the disease.
    evidence:
    - reference: PMID:9770558
      reference_title: "Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "When age and sex were controlled for in a multivariate analysis, low urinary iodine, high serum thyrotropin, and low serum thyroxine-binding globulin values were associated with an increased risk of Kashin-Beck disease, but a low serum selenium concentration was not."
      explanation: Names high serum thyrotropin among the independently associated markers.
  evidence:
  - reference: PMID:9770558
    reference_title: "Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "hypothyroidism was more frequent (23 percent vs. 4 percent, P=0.01)."
    explanation: >-
      Graded INDIRECT: the sentence reports the hypothyroidism rate rather than the
      thyrotropin value, and a raised thyrotropin is what defines hypothyroidism here.

- name: Serum thyroxine-binding globulin
  presence: Decreased
  biomarker_term:
    preferred_term: serum thyroxine-binding globulin
    term:
      id: NCIT:C106005
      label: Thyroxine-Binding Globulin
  notes: >-
    The third thyroid marker retained by the multivariate model. Curated for
    completeness of that result rather than because a mechanism is proposed for it -
    nothing in this entry explains why a low binding globulin should accompany the
    disease.
  readouts:
  - target: Iodine Deficiency and Hypothyroidism
    relationship: CORRELATES_WITH
    direction: NEGATIVE
    endpoint_context: DIAGNOSTIC
    interpretation: >-
      Recorded CORRELATES_WITH rather than READOUT_OF: it was independently associated
      with the disease in the same model, but this entry curates no account of what it
      is measuring here.
    evidence:
    - reference: PMID:9770558
      reference_title: "Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "When age and sex were controlled for in a multivariate analysis, low urinary iodine, high serum thyrotropin, and low serum thyroxine-binding globulin values were associated with an increased risk of Kashin-Beck disease, but a low serum selenium concentration was not."
      explanation: Names low serum thyroxine-binding globulin among the independently associated markers.
  evidence:
  - reference: PMID:9770558
    reference_title: "Kashin-Beck osteoarthropathy in rural Tibet in relation to selenium and iodine status."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "When age and sex were controlled for in a multivariate analysis, low urinary iodine, high serum thyrotropin, and low serum thyroxine-binding globulin values were associated with an increased risk of Kashin-Beck disease, but a low serum selenium concentration was not."
    explanation: The multivariate result, which is the only evidence this entry has for this marker.

epidemiology:
- name: Early-Onset Endemic Distribution with Family Aggregation
  description: >-
    The disease starts in childhood, usually between three and twelve years of
    age, affects both sexes equally, clusters in agricultural areas and within
    families, and fluctuates year to year. The family clustering is a
    gene-environment ambiguity rather than a genetic finding: families share
    genes and also share grain stores and wells.
  evidence:
  - reference: PMID:31548049
    reference_title: "Endemic Kashin-Beck disease: A food-sourced osteoarthropathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Epidemiology of the KBD was characterized by early-onset, gender equality, agricultural area, regional discrepancy, family aggregation, annual fluctuation, etc."
    explanation: The epidemiological signature this record names, in the source's own list.
  - reference: PMID:40963707
    reference_title: "Prevalence and Risk Factors of Depression in Patients With Endemic Osteoarthritis Kashin-Beck Disease."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Kashin-Beck disease (KBD) is an endemic osteoarthropathy, which occurs in children aged 3-12, with similarity to osteoarthritis (OA)."
    explanation: >-
      The onset window. Graded OTHER: a background sentence rather than the
      study's own result.

progression:
- phase: Childhood Growth-Plate Phase
  notes: >-
    While the growth plates are open, the disease produces its defining
    lesions - brachydactyly, enlarged joints, short stature. This is the phase
    intervention can prevent, and the phase in which selenium and water measures
    show clinical improvement.
  evidence:
  - reference: PMID:31490368
    reference_title: "Prevention and control strategies for children Kashin-Beck disease in China: A systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Comprehensive measures and change of grain were the most effective measures in preventing new case, whereas improvement of water and salt-rich selenium resulted in clinical improvements in children KBD."
    explanation: >-
      That the intervention literature is entirely about children is the
      evidence for treating this as the modifiable phase.
  - reference: PMID:40963707
    reference_title: "Prevalence and Risk Factors of Depression in Patients With Endemic Osteoarthritis Kashin-Beck Disease."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Kashin-Beck disease (KBD) is an endemic osteoarthropathy, which occurs in children aged 3-12, with similarity to osteoarthritis (OA)."
    explanation: The age window this phase covers.

- phase: Adult Degenerative Phase
  notes: >-
    After growth stops the skeletal deformity is fixed and what continues is
    joint degeneration - pain, stiffness, and radiographic change graded like
    osteoarthritis. Adult management is symptomatic: chondroitin, glucosamine,
    intra-articular hyaluronic acid and NSAIDs relieve symptoms, and every adult
    treatment curated here targets the arthropathy node rather than anything
    upstream of it.
  evidence:
  - reference: PMID:41342918
    reference_title: "Study on radiographic grading of ankle joint in adult patients with Kashin-Beck disease in Shaanxi and Gansu Province, China."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This paper aims to establish an X-ray imaging grading for assessing ankle joints in adult Kashin-Beck disease (KBD) and investigate its correlation with clinical grading of finger and ankle pain."
    explanation: The adult phase as its own clinical problem, with its own grading need.
  - reference: PMID:31376086
    reference_title: "The effectiveness of treatments for Kashin-Beck disease: a systematic review and network meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Chondroitin, glucosamine, IAH and nonsteroid anti-inflammatory drugs are effective for symptom improvements of KBD in adults."
    explanation: >-
      The adult treatment literature is symptomatic throughout - this is the
      evidence for the claim in the notes, which an earlier draft asserted
      without one.

animal_models:
- name: T-2 toxin plus selenium-deficient diet rat
  species: Rat
  genotype: Wild type
  description: >-
    Sprague-Dawley rats fed a selenium-deficient diet for four weeks and then
    exposed to T-2 toxin for four more. The field's workhorse model, and the one
    that makes the compound-etiology hypothesis tractable: the deep-zone lesion
    that resembles the human disease appears only in the groups given both.
  publication: PMID:22258458
  modeled_mechanisms:
  - target: Mixed-Mode Chondrocyte Death in Deep and Middle Cartilage Zones
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: TISSUE
    description: >-
      Apoptosis and necroptosis co-exist in the middle zone of the model's
      cartilage, as they do in children with the disease, and the deep-zone
      chondronecrosis is described as very similar to the human lesion.
    limitations: >-
      A four-week rodent exposure is not a childhood in an endemic village, and
      the model delivers a fixed toxin dose rather than the variable, seasonal
      contamination of a real grain store. It also cannot address the
      fulvic-acid or iodine hypotheses, since neither water composition nor
      iodine status is a variable in it.
    divergences:
    - divergence_type: TEMPORAL_SCOPE
      materiality: QUALIFYING
      description: >-
        Weeks of controlled feeding stand in for years of intermittent childhood
        exposure during active growth; the model compresses the timescale the
        disease is defined on.
    - divergence_type: BOUNDARY_OMISSION
      materiality: QUALIFYING
      description: >-
        Drinking-water composition and iodine status are outside the model, so
        it cannot speak to two of the four hypotheses this entry curates.
    evidence:
    - reference: PMID:30680829
      reference_title: "Death of chondrocytes in Kashin-Beck disease: Apoptosis, necrosis or necroptosis?"
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Apoptosis and necroptosis co-existed in the middle zone in this rat KBD model."
      explanation: >-
        The specific correspondence between model and human cartilage - the same
        two death modes in the same zone.
    - reference: PMID:22258458
      reference_title: "Histopathology of chondronecrosis development in knee articular cartilage in a rat model of Kashin-Beck disease using T-2 toxin and selenium deficiency conditions."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Chondronecrosis in deep zone of articular cartilage of knee joints was seen in both the low and high T-2 toxin plus selenium-deficient diet groups, these chondronecrotic lesions being very similar to chondronecrosis observed in human KBD."
      explanation: >-
        The primary report of the deep-zone lesion, and the dose design that
        shows both exposures are needed for it.
  - target: Endochondral Ossification Failure at the Growth Plate
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    model_scale: TISSUE
    description: >-
      The rat's growth-plate chondronecrosis is explicitly not similar to the
      human lesion, which is the failure this entry records rather than smooths
      over. The primary report attributes it to the rat's growth plates never
      closing.
    limitations: >-
      The rat does not close its growth plates, so the epiphyseal closure that
      defines the human childhood disease cannot occur. Any inference from this
      model to the growth-plate node is therefore unsafe, and the model's value
      is at the articular cartilage instead.
    divergences:
    - divergence_type: SPECIES_MISMATCH
      materiality: INVALIDATING
      description: >-
        Rat epiphyseal growth plates remain open through life. The human disease
        is defined by damage to a plate that then closes early, and the model
        has no counterpart to that event.
    evidence:
    - reference: PMID:22258458
      reference_title: "Histopathology of chondronecrosis development in knee articular cartilage in a rat model of Kashin-Beck disease using T-2 toxin and selenium deficiency conditions."
      supports: REFUTE
      evidence_source: MODEL_ORGANISM
      snippet: "However, the chondronecrosis observed in the rat epiphyseal growth plates of animals treated with T-2 toxin alone or T-2 toxin plus selenium-deficient diets were not similar to that found in human KBD."
      explanation: >-
        The negative result stated by the model's own authors, in both the
        toxin-alone and the combined groups.
    - reference: PMID:22258458
      reference_title: "Histopathology of chondronecrosis development in knee articular cartilage in a rat model of Kashin-Beck disease using T-2 toxin and selenium deficiency conditions."
      supports: REFUTE
      evidence_source: MODEL_ORGANISM
      snippet: "However, those changes seen in epiphyseal growth plate differ from those seen in human KBD probably because of the absence of growth plate closure in the rat."
      explanation: The authors' explanation for the failure, which is the species divergence recorded above.
  - target: Selenoenzyme Antioxidant Capacity Deficit
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: MOLECULAR
    description: >-
      The model reproduces the biochemical deficit directly: antioxidant enzyme
      activity and mRNA down, lipid peroxidation up, in both serum and
      cartilage.
    limitations: >-
      The measurements are of the model's own biochemistry; no matching serum or
      cartilage antioxidant panel from patients is curated in this entry, so the
      correspondence to human tissue is assumed rather than shown here.
    evidence:
    - reference: PMID:22294316
      reference_title: "Oxidant damage in Kashin-Beck disease and a rat Kashin-Beck disease model by employing T-2 toxin treatment under selenium deficient conditions."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "The levels of thiobarbituric acid reactive substances (TBARS), indicative of lipid peroxidation in serum and cartilage, were significantly increased in all experimental groups compared to the normal diet group, while the levels of antioxidants, measured as total antioxidant capacity (T-AOC), catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidases (GPX), in serum and cartilage were significantly lower than that in the normal diet group."
      explanation: The antioxidant and lipid-peroxidation measurements this link rests on.
  evidence:
  - reference: PMID:35304334
    reference_title: "Animal models of Kashin-Beck disease exposed to environmental risk factors: Methods and comparisons."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In conclusion, the rhesus monkeys administrated endemic water and grain were susceptible animals to replicate KBD. The rats treated with T-2 toxin combined with Se/nutrition deficiency could be a suitable and widely used animal model."
    explanation: The review's assessment of this model as the suitable and widely used one.

- name: Low-nutrition diet plus T-2 toxin rat
  species: Rat
  genotype: Wild type
  description: >-
    A variant of the workhorse model in which the deficient diet is low in
    protein, iodine and selenium together rather than in selenium alone - which
    makes it the only model in this entry that includes the iodine arm.
  publication: PMID:23701828
  modeled_mechanisms:
  - target: Endochondral Ossification Failure at the Growth Plate
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    model_scale: TISSUE
    description: >-
      Blurred, thin and irregular epiphyseal plates with chondrocyte necrosis
      and shortened tibias, which the authors read as closely matching the human
      bone changes.
    limitations: >-
      Recorded PARTIALLY_RECAPITULATES rather than RECAPITULATES because the
      companion model above found rat growth-plate chondronecrosis explicitly
      unlike the human lesion, and this study does not address that objection.
      The diet also varies three nutrients at once, so it cannot separate the
      iodine, protein and selenium contributions it bundles.
    divergences:
    - divergence_type: SPECIES_MISMATCH
      materiality: QUALIFYING
      description: >-
        As with the selenium-deficient model, the rat growth plate does not
        close, so the human disease's defining endpoint has no counterpart.
    - divergence_type: BOUNDARY_OMISSION
      materiality: QUALIFYING
      description: >-
        Three dietary deficiencies are applied together and no arm varies them
        independently, so the model cannot attribute its effect to any one.
    evidence:
    - reference: PMID:23701828
      reference_title: "An animal model of Kashin-Beck disease induced by a low-nutrition diet and exposure to T-2 toxin."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "In group D, all epiphyseal plates were blurred, thin, and irregular."
      explanation: The radiographic plate finding in the combined group.
    - reference: PMID:23701828
      reference_title: "An animal model of Kashin-Beck disease induced by a low-nutrition diet and exposure to T-2 toxin."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "A rat model of KBD induced by a low-nutrition diet and T-2 toxin exposure demonstrated radiographic and histopathological abnormalities of the proximal epiphyseal plate and the tibial metaphysis that are very similar to the bone changes found in patients with KBD."
      explanation: The authors' own assessment of the correspondence to patients.

- name: Rhesus monkey fed endemic water and grain
  species: Rhesus monkey
  genotype: Wild type
  description: >-
    Monkeys given the actual water and grain from endemic villages, rather than
    isolated candidate agents. Assessed as the most susceptible species for
    replicating the disease - and the design is the point: it tests the endemic
    environment as a whole instead of pre-judging which constituent matters.
  publication: PMID:35304334
  modeled_mechanisms:
  - target: Dietary T-2 Toxin Exposure
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: ORGANISM
    description: >-
      Reproduces the disease using the endemic exposure itself rather than a
      reconstructed one.
    limitations: >-
      Because it delivers the whole environment, it cannot say which constituent
      is responsible - the same strength and weakness. The only source curated
      for it here is a methods review; the primary reports of the original
      monkey experiments were not obtained, so the experimental detail is not
      curated.
    divergences:
    - divergence_type: CONTESTED_ASSUMPTION
      materiality: QUALIFYING
      description: >-
        The model assumes the causative agent is present in the endemic water
        and grain. That is the hypothesis under test, so a positive result
        supports the compound etiology without discriminating among its parts.
    evidence:
    - reference: PMID:35304334
      reference_title: "Animal models of Kashin-Beck disease exposed to environmental risk factors: Methods and comparisons."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "In conclusion, the rhesus monkeys administrated endemic water and grain were susceptible animals to replicate KBD. The rats treated with T-2 toxin combined with Se/nutrition deficiency could be a suitable and widely used animal model."
      explanation: The review's assessment of the rhesus monkey as the susceptible species.

discussions:
- discussion_id: kbd_etiology_unresolved
  kind: CONTROVERSY
  prompt: >-
    Which environmental factor - selenium deficiency, iodine deficiency, T-2
    toxin, a water constituent, or an obligate combination - actually causes
    Kashin-Beck disease?
  rationale: >-
    Seventy years of work has produced four standing single-factor hypotheses
    and no resolution, which is why this entry curates all of them alongside the
    compound reading rather than asserting one. Recorded as a CONTROVERSY rather
    than a knowledge gap: the positions are published and in live disagreement,
    not merely absent. Each has real support and a real problem. Selenium
    deficiency has the selenoprotein association data and the preventive trials
    - but soil selenium is as low in non-endemic villages, and a randomised
    trial found selenium useless for established disease once iodine was
    replaced. Iodine deficiency survives multivariate adjustment where selenium
    does not, and its replacement restored growth - but no cartilage-level
    mechanism connects it to the lesion. T-2 toxin has the best animal model and
    the most effective intervention - but the model needs a deficient diet
    alongside it, and the growth-plate lesion it produces is explicitly unlike
    the human one. Fulvic acid has the water-improvement result and a 1999
    free-radical mechanism, and almost nothing since. The gap matters because
    the disease is being eliminated by measures that address all of them at
    once, so the natural experiment that would separate them is closing.
  attaches_to:
  - pathophysiology#Chronic Dietary Selenium Deficiency
  - pathophysiology#Dietary T-2 Toxin Exposure
  - pathophysiology#Iodine Deficiency and Hypothyroidism
  - pathophysiology#Fulvic Acid Free-Radical Generation in Cartilage
  - mechanistic_hypotheses#compound_etiology
  evidence:
  - reference: PMID:11482536
    reference_title: "Kashin-Beck disease: from etiology to prevention or from prevention to etiology?"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Although none of the competing theories prevails when they are compared using a predefined and standard set of causality criteria (temporality, strength of the association, biological gradient, experimental evidence, biological plausibility, coherence, specificity and analogy), none should be discounted."
    explanation: The causality review's verdict, which is the state this discussion records.
  - reference: PMID:11482536
    reference_title: "Kashin-Beck disease: from etiology to prevention or from prevention to etiology?"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Well-conducted randomised intervention should be the priority of researchers as well as public health professionals to demonstrate what works and what does not."
    explanation: >-
      And its recommendation, which is why the entry curates the preventive
      trial evidence in as much detail as the mechanistic evidence.

- discussion_id: kbd_death_mode
  kind: INTERPRETATION
  prompt: >-
    Is the chondrocyte death in Kashin-Beck disease apoptosis, necrosis,
    necroptosis, or ferroptosis?
  rationale: >-
    The answer appears to be "several, sorted by cartilage zone", which is
    unusual enough to be worth stating rather than smoothing. Caspase-3 is not
    raised in patient cartilage, so classic apoptosis is not the main event;
    RIP3 positivity puts necroptosis in the middle zone; ultrastructure shows
    frank necrosis in the deep zone; mitochondrial dysfunction with cytochrome c
    release and caspase-9 activation is measurable in cultured patient
    chondrocytes; and the ferroptosis work adds a further mode driven
    specifically by the toxin. The Smad2/Smad3 result supplies a mechanism for
    the split - the two proteins are lost together under oxidative stress and
    each loss produces a different death. This entry therefore curates one node
    for mixed-mode death plus separate ferroptosis and mitochondrial nodes,
    rather than choosing a mode.
  attaches_to:
  - pathophysiology#Mixed-Mode Chondrocyte Death in Deep and Middle Cartilage Zones
  - pathophysiology#Ferroptotic Chondrocyte Death
  - pathophysiology#Chondrocyte Mitochondrial Dysfunction
  - pathophysiology#Smad2 and Smad3 Depletion

- discussion_id: kbd_vascular_direction
  kind: INTERPRETATION
  prompt: >-
    Is the epiphyseal plate in Kashin-Beck disease under-vascularised or
    over-vascularised?
  rationale: >-
    Two curated observations point opposite ways, and this entry records both
    rather than choosing. The 2001 histology of phalanges from affected children
    found the proximal cartilage end plate unvascularised, and proposed that the
    disease develops from a failure of metaphyseal angiogenesis. The 2026 type H
    vessel work found the opposite in the rat - vessels proliferating at the
    epiphyseal plate, delivering more toxin, with the loop demonstrated
    pharmacologically in both directions. They are not necessarily in conflict:
    different species, different bones, different stages, and "vascularisation
    of the cartilage end plate" and "type H vessel density at the plate" are not
    the same measurement. But nothing curated here reconciles them, and the
    pathograph currently carries only the proliferative reading as an edge.
  attaches_to:
  - pathophysiology#Type H Vessel Proliferation at the Epiphyseal Plate
  - pathophysiology#Endochondral Ossification Failure at the Growth Plate
  evidence:
  - reference: PMID:11482529
    reference_title: "Histology of Kashin-Beck lesions."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These observations suggest that Kashin-Beck disease could develop from an alteration of the angiogenesis of the metaphyseal cartilage resulting in degeneration with consequent joint dysplasia, which may be associated with a decrease in growth of the diaphyseal bones."
    explanation: The angiogenesis-failure reading, from human phalangeal histology.
  - reference: PMID:42000119
    reference_title: "A self-perpetuating cycle of Type H vessel proliferation and T-2 induced inflammation drives KBD pathogenesis."
    supports: REFUTE
    evidence_source: MODEL_ORGANISM
    snippet: "Conversely, HF reduced type H vessel proliferation (MD: -3.70, 95%CI: -6.67, -0.73), decreased T-2 toxin levels and suppressed inflammation (MD: -0.17, 95%CI: -0.23, -0.11), while preserving proteoglycan content and cartilage morphology."
    explanation: >-
      Graded REFUTE against the angiogenesis-failure reading: suppressing vessel
      proliferation protected the cartilage, which is the opposite of what a
      model of insufficient vascularisation predicts.

datasets:
- accession: geo:GSE246097
  title: "Integration of miRNA in exosomes and single-cell RNA-seq profiles in endemic osteoarthritis, Kashin-Beck disease"
  description: >-
    Serum and chondrocyte exosomal miRNA sequencing integrated with single-cell
    RNA-seq of patient chondrocytes - the only single-cell resource this
    session identified for the disease. Typed MULTI_OMICS because it is two assay types analysed
    together rather than either one alone.
  data_type: MULTI_OMICS
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  publication: PMID:38156801
  evidence:
  - reference: GEO:GSE246097
    reference_title: "Integration of miRNA in exosomes and single-cell RNA-seq profiles in endemic osteoarthritis, Kashin-Beck disease"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "We isolated serum and chondrocytes-derived exosomes, miRNA sequencing revealed exosomes miRNA profiles and differentially expressed miRNAs (DE-miRNAs) were identified."
    explanation: >-
      The exosomal miRNA half of the series, from GEO's own summary. Graded OTHER: a
      repository record describing its contents, not a study result.
  - reference: GEO:GSE246097
    reference_title: "Integration of miRNA in exosomes and single-cell RNA-seq profiles in endemic osteoarthritis, Kashin-Beck disease"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Single-cell RNA sequencing (scRNA-seq) was performed to identify chondrocyte clusters and their gene signatures in KBD."
    explanation: The single-cell half, which is what makes this series the only one of its kind here.

- accession: geo:GSE186593
  title: "Comprehensive expression profiles of mRNAs, lncRNAs and miRNAs in Kashin-Beck Disease identified by RNA-sequencing"
  description: >-
    mRNA, lncRNA and miRNA expression profiles from Kashin-Beck disease
    cartilage.
  data_type: BULK_RNA_SEQ
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  publication: PMID:34913457
  evidence:
  - reference: GEO:GSE186593
    reference_title: "Comprehensive expression profiles of mRNAs, lncRNAs and miRNAs in Kashin-Beck Disease identified by RNA-sequencing"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "RNA‐seq technology to detect the differentially expressed mRNAs, lncRNAs and miRNAs in KBD patients."
    explanation: >-
      The assay and the three RNA classes profiled, from GEO's own summary. Graded
      OTHER as a repository record rather than a study result.

- accession: geo:GSE59446
  title: "Human Peripheral blood mononuclear cells (PBMCs): Control vs. Kashin-Beck Disease"
  description: >-
    Peripheral blood mononuclear cell expression profiling, cases versus
    controls, and the largest of the available series at 200 samples.
  data_type: MICROARRAY
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  evidence:
  - reference: GEO:GSE59446
    reference_title: "Human Peripheral blood mononuclear cells (PBMCs): Control vs. Kashin-Beck Disease"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Gene expression analysis was conducted of peripheral blood samples from 100 patients with KBD and 100 controls randomly chosen from two KBD-endemic areas"
    explanation: >-
      The design and the sample count. Graded OTHER as a repository record rather than
      a study result.
  - reference: GEO:GSE59446
    reference_title: "Human Peripheral blood mononuclear cells (PBMCs): Control vs. Kashin-Beck Disease"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Objective:To identify an accurate blood-based gene signature for early detection of Kashin-Beck disease (KBD)."
    explanation: The stated purpose of the series - an early-detection blood signature.
  notes: >-
    The cached record says only "Gene expression analysis", so the assay type is
    not readable from it, and neither quoted snippet above names it. MICROARRAY is
    recorded on the GEO series metadata itself, which types the series as
    "Expression profiling by array" on platform GPL18887.

- accession: geo:GSE311894
  title: "Effects of Selenium-mediated RUNX2 Overexpression and its Transcriptome Alterations on Chondrocyte Injury in Kashin Beck disease"
  description: >-
    RNA-seq of human chondrocytes with lentiviral RUNX2 overexpression versus
    controls. Note this is an engineered cell model, not patient material: the
    series title names the disease but the experiment manipulates RUNX2
    directly.
  data_type: BULK_RNA_SEQ
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  publication: PMID:41425094
  evidence:
  - reference: GEO:GSE311894
    reference_title: "Effects of Selenium-mediated RUNX2 Overexpression and its Transcriptome Alterations on Chondrocyte Injury in Kashin Beck disease"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "we established a RUNX2 overexpression model using lentiviral transfection in human chondrocytes."
    explanation: >-
      What the experiment actually is, quoted so the caveat in `notes` below is
      checkable from the record rather than taken on trust. Graded OTHER as a
      repository record.
  - reference: GEO:GSE311894
    reference_title: "Effects of Selenium-mediated RUNX2 Overexpression and its Transcriptome Alterations on Chondrocyte Injury in Kashin Beck disease"
    supports: NO_EVIDENCE
    evidence_source: OTHER
    snippet: "These results provide a comprehensive transcriptomic resource for understanding RUNX2-mediated signaling in cartilage degeneration and may contribute to elucidating the molecular pathogenesis of osteoarthropathy such as Kashin-Beck disease."
    explanation: >-
      Graded NO_EVIDENCE deliberately. This is the sentence that connects the series
      to the disease, and it claims only that the data "may contribute to elucidating"
      the pathogenesis of osteoarthropathy "such as" Kashin-Beck disease - a resource
      claim, not a finding about this disease. Recording it as NO_EVIDENCE is why the
      series carries no pathophysiology node.
  notes: >-
    Listed as a resource, not as support for a claim. The entry curates no RUNX2
    pathophysiology node: the series is a lentiviral overexpression model in
    cultured chondrocytes whose connection to the disease is the authors' own
    inference, and this entry does not quote the accompanying paper.

notes: >-
  Why this entry exists. Kashin-Beck disease is the knowledge base's clearest
  case of a disease with a settled clinical picture and an unsettled cause. The
  lesion, the tissue and the natural history are not in dispute; the
  environmental agent has been argued for seventy years. Rather than pick a
  winner, the entry curates the compound reading as CANONICAL and the four
  single-factor hypotheses as ALTERNATIVE, and tags causal edges with the
  hypothesis groups they belong to, so a reader can see which parts of the chain
  depend on which etiology. All four single-factor groups now tag at least one
  edge; `compound_etiology` tags the two initiating exposures it combines.

  On the deep-research report. It needed heavy discounting: its own validation
  recorded four of six checked quotes as absent from the papers they were
  attributed to, three unresolved references, and nine mislabelled ontology
  terms - among them `CL:0000605` offered for "articular chondrocyte" when it is
  *fungal asexual spore*, `UBERON:0000004` for "ankle joint region" when it is
  *nose*, and `UBERON:0001415` for "interphalangeal joint" when it is *skin of
  pelvis*. None of the nine is bound anywhere in this entry. Two CURIEs the
  report flagged with hedged labels were checked and are correct as identifiers
  - `GO:0097707` (ferroptosis) and `CL:0000743` (hypertrophic chondrocyte) - and
  are used here under their real ontology labels. Every snippet in this entry
  was copied from a reference cache fetched and read directly rather than from
  the report; three of the papers cited here (PMID:35304334, PMID:31490368 and
  PMID:41342918) do also appear in the report, and two snippets used here appear
  in it as quoted text - the four-hypotheses sentence at report line 620 and the
  prevention-ranking sentence at report line 969 - so "found independently"
  would be too strong a claim for those and is not made. Both of the report's
  versions are truncated or mis-transcribed relative to the cached source, which
  is why the snippets here were taken from the cache instead.

  Negative and refuting results are curated on purpose, because in this disease
  they carry most of the information. The selenoprotein meta-analysis found
  GPX1, GPX4, SEPP1 and TrxR2 *not* associated with susceptibility, and a
  Tibetan replication found no single-SNP association at all. The randomised
  Tibetan supplementation trial found selenium had no effect on established
  disease once iodine was corrected. The network meta-analysis reports vitamin C
  and aspirin as effective for radiographic structure and, in the same abstract,
  as not established. The workhorse rat model explicitly fails to reproduce the
  human growth-plate lesion. Each of these is recorded as a REFUTE item against
  the claim it bears on, next to the positive evidence, rather than omitted.

  Deliberate non-bindings, so they are not re-litigated. Both the selenium and
  iodine `exposure_term`s are unbound because every ECTO selenium and iodine term
  denotes the element being present, which is the opposite of the exposure; the note
  on the selenium entry records `ECTO:0400019` "exposure to decreased protein in food"
  as the template a new-term request should follow. All three histopathology
  `finding_term`s are unbound because each is a multi-part post-composition and NCIT's
  closest term, `NCIT:C36184` (Necrosis), names one component of three. Two GO
  bindings are deliberately broader than the claim they carry - `GO:0002062`
  (chondrocyte differentiation) for the terminal step alone, and `GO:0022900`
  (electron transport chain) for the mitochondrial respiratory chain - and each says so
  in a note beside it, with the specificity carried in `preferred_term`.

  On evidence attached to `target_mechanisms` links. Three of the ten treatment
  links carry their own evidence - both new joint-directed records and iodine
  replacement - because for those there is a result about the *node* rather than
  about the disease. The other seven do not, and that is a decision rather than an
  omission. The four public-health interventions are supported by pooled incidence
  odds ratios, and incidence is not a measurement of the exposure node the link
  points at; reusing those snippets on the links would make one sentence do double
  duty for a claim it does not make. The adult symptomatic drugs are supported by
  pain effect sizes, which likewise measure the outcome rather than the arthropathy
  node. Where a real node-level result appears for any of them, the link should get
  it.

  On the Chinese national clinical grading. Degrees I to III are the operative
  severity scale in this literature and the axis the burden data are stratified by, and
  they are deliberately not modelled as `stages:`. `progression:` holds the two-phase
  natural history, which is a different axis - a phase of the disease, not a severity
  tier - and `diagnosis:` holds the radiographic grading schemes. The grading's own
  definitional content sits in WS/T 207-2010, whose text was not obtained here, so a
  `stages:` block would be three names with no criteria behind them. It is recorded as
  an open item rather than filled in badly.

  Not curated, and why. A further 24 references were fetched and read during
  this session and are not cited here: gut-microbiome and faecal-metabolomic
  profiling (PMID:34711812, PMID:37960304), SIRT3 and WISP1 work
  (PMID:42559309, PMID:38003226), p-ATF2 and Zip6 expression studies, spatial
  and health-loss epidemiology (PMID:33375039, PMID:41255597, PMID:41984302,
  PMID:42205027), and three deep-learning radiographic classifiers. These were
  read and judged out of scope for a first entry rather than left unverified:
  the omics work is association-level and would need a mechanism node this entry
  cannot yet support, and the imaging-classifier papers describe tools rather
  than disease mechanism. Their caches are deliberately not committed with this
  entry, so every `references_cache` file in this changeset is one this entry
  actually cites. PMID:41425094 is the exception in the other direction: its
  cache is committed because the entry links it as the `publication` of
  `geo:GSE311894`, but the entry quotes nothing from it - what it quotes for that
  series is the GEO record itself, including the hedged "may contribute to
  elucidating" sentence, graded `NO_EVIDENCE`.

📚

References & Deep Research

Deep Research

1

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (2)

Record notes

Why this entry exists. Kashin-Beck disease is the knowledge base's clearest case of a disease with a settled clinical picture and an unsettled cause. The lesion, the tissue and the natural history are not in dispute; the environmental agent has been argued for seventy years. Rather than pick a winner, the entry curates the compound reading as CANONICAL and the four single-factor hypotheses as ALTERNATIVE, and tags causal edges with the hypothesis groups they belong to, so a reader can see which parts of the chain depend on which etiology. All four single-factor groups now tag at least one edge; `compound_etiology` tags the two initiating exposures it combines. On the deep-research report. It needed heavy discounting: its own validation recorded four of six checked quotes as absent from the papers they were attributed to, three unresolved references, and nine mislabelled ontology terms - among them `CL:0000605` offered for "articular chondrocyte" when it is *fungal asexual spore*, `UBERON:0000004` for "ankle joint region" when it is *nose*, and `UBERON:0001415` for "interphalangeal joint" when it is *skin of pelvis*. None of the nine is bound anywhere in this entry. Two CURIEs the report flagged with hedged labels were checked and are correct as identifiers - `GO:0097707` (ferroptosis) and `CL:0000743` (hypertrophic chondrocyte) - and are used here under their real ontology labels. Every snippet in this entry was copied from a reference cache fetched and read directly rather than from the report; three of the papers cited here (PMID:35304334, PMID:31490368 and PMID:41342918) do also appear in the report, and two snippets used here appear in it as quoted text - the four-hypotheses sentence at report line 620 and the prevention-ranking sentence at report line 969 - so "found independently" would be too strong a claim for those and is not made. Both of the report's versions are truncated or mis-transcribed relative to the cached source, which is why the snippets here were taken from the cache instead. Negative and refuting results are curated on purpose, because in this disease they carry most of the information. The selenoprotein meta-analysis found GPX1, GPX4, SEPP1 and TrxR2 *not* associated with susceptibility, and a Tibetan replication found no single-SNP association at all. The randomised Tibetan supplementation trial found selenium had no effect on established disease once iodine was corrected. The network meta-analysis reports vitamin C and aspirin as effective for radiographic structure and, in the same abstract, as not established. The workhorse rat model explicitly fails to reproduce the human growth-plate lesion. Each of these is recorded as a REFUTE item against the claim it bears on, next to the positive evidence, rather than omitted. Deliberate non-bindings, so they are not re-litigated. Both the selenium and iodine `exposure_term`s are unbound because every ECTO selenium and iodine term denotes the element being present, which is the opposite of the exposure; the note on the selenium entry records `ECTO:0400019` "exposure to decreased protein in food" as the template a new-term request should follow. All three histopathology `finding_term`s are unbound because each is a multi-part post-composition and NCIT's closest term, `NCIT:C36184` (Necrosis), names one component of three. Two GO bindings are deliberately broader than the claim they carry - `GO:0002062` (chondrocyte differentiation) for the terminal step alone, and `GO:0022900` (electron transport chain) for the mitochondrial respiratory chain - and each says so in a note beside it, with the specificity carried in `preferred_term`. On evidence attached to `target_mechanisms` links. Three of the ten treatment links carry their own evidence - both new joint-directed records and iodine replacement - because for those there is a result about the *node* rather than about the disease. The other seven do not, and that is a decision rather than an omission. The four public-health interventions are supported by pooled incidence odds ratios, and incidence is not a measurement of the exposure node the link points at; reusing those snippets on the links would make one sentence do double duty for a claim it does not make. The adult symptomatic drugs are supported by pain effect sizes, which likewise measure the outcome rather than the arthropathy node. Where a real node-level result appears for any of them, the link should get it. On the Chinese national clinical grading. Degrees I to III are the operative severity scale in this literature and the axis the burden data are stratified by, and they are deliberately not modelled as `stages:`. `progression:` holds the two-phase natural history, which is a different axis - a phase of the disease, not a severity tier - and `diagnosis:` holds the radiographic grading schemes. The grading's own definitional content sits in WS/T 207-2010, whose text was not obtained here, so a `stages:` block would be three names with no criteria behind them. It is recorded as an open item rather than filled in badly. Not curated, and why. A further 24 references were fetched and read during this session and are not cited here: gut-microbiome and faecal-metabolomic profiling (PMID:34711812, PMID:37960304), SIRT3 and WISP1 work (PMID:42559309, PMID:38003226), p-ATF2 and Zip6 expression studies, spatial and health-loss epidemiology (PMID:33375039, PMID:41255597, PMID:41984302, PMID:42205027), and three deep-learning radiographic classifiers. These were read and judged out of scope for a first entry rather than left unverified: the omics work is association-level and would need a mechanism node this entry cannot yet support, and the imaging-classifier papers describe tools rather than disease mechanism. Their caches are deliberately not committed with this entry, so every `references_cache` file in this changeset is one this entry actually cites. PMID:41425094 is the exception in the other direction: its cache is committed because the entry links it as the `publication` of `geo:GSE311894`, but the entry quotes nothing from it - what it quotes for that series is the GEO record itself, including the hedged "may contribute to elucidating" sentence, graded `NO_EVIDENCE`.

Create: Kashin-Beck Disease · 2026-09-07T15:17:00Z · View source

New disorder entry for Kashin-Beck disease (MONDO:0005610), an endemic environmental osteochondropathy of children in the Siberia-China-Tibet belt. Curated as an environmental-exposure entry: the clinical picture is settled and the causal agent is not, so the entry curates the compound-etiology reading as CANONICAL and four single-factor hypotheses (selenium deficiency, iodine deficiency, T-2 mycotoxin, fulvic acid in drinking water) as ALTERNATIVE, with every group tagging at least one causal edge. Content. 16 pathophysiology nodes running from four initiating exposure nodes through selenoenzyme loss, Wnt derepression, chondrocyte oxidative stress, mitochondrial dysfunction, Smad2/Smad3 depletion and ferroptosis to mixed-mode chondrocyte death, then splitting into growth-plate ossification failure and articular matrix degradation. 7 phenotypes, 3 histopathology records, 4 environmental exposures (T-2 toxin, low selenium, low iodine, and fluoride as an EXACERBATES modifier acting through CES1-mediated T-2 detoxification), 5 genetic records, 3 diagnosis records, 2 differential diagnoses, 8 treatments, 2 prevalence records, a clinical_burden assessment, 3 animal models with typed divergences, 3 discussions, 4 GEO datasets. Deep research. Provider was claude_code (research/Kashin-Beck_Disease-deep- research-claude_code.md). The report needed heavy discounting - its own validation recorded 4 of 6 checked quotes as absent from the papers they were attributed to, 3 unresolved references and 9 mislabelled ontology terms. None of the 9 mislabelled CURIEs is bound in the entry. The report was used for structure and leads; every snippet was taken from a reference cache fetched with `just fetch-reference` and read directly. Where a snippet also appears in the report as quoted text, the entry says so in `notes` rather than claiming independent discovery. Pre-PR red team. An adversarial review of the first draft returned REQUEST_CHANGES with 26 findings, all of the same shape: prose asserting more than the file own evidence. All were addressed before this record. The substantive ones: both prevalence records were misclassified (an incidence recorded as POINT_PREVALENCE, and a band three orders of magnitude out - BELOW_1_IN_1000000 for 180 per 100,000); the claim that susceptibility maps to selenoprotein genes rather than cartilage structural genes was retracted in three places and replaced with an ADAM12 record, since the meta-analysis it rested on searched only on the term "selenoprotein" and a cached GWAS reports ADAM12 at p = 9.25e-9; the Brachydactyly record was re-sourced (its only evidence had been a methods sentence that does not mention brachydactyly); HP:0005920 was rebound to HP:0003037; the bundled initiating node was split into separate selenium and T-2 nodes, and the bundled growth-plate node into ossification failure and matrix degradation; three CANONICAL hypotheses were reduced to one; the etiology discussion was re-kinded KNOWLEDGE_GAP -> CONTROVERSY; and a false `notes` sentence saying the omitted topics "trace to sources this session did not fetch and verify" was removed - those sources had been fetched. Reference consumption. 49 fetched-but-unused caches were resolved by consuming 25 of them and pruning the rest. Newly consumed: the treatment network meta-analysis (PMID:31376086, which closed a gap where the entry curated no adult treatment at all), the Tibetan iodine study (PMID:9770558) and supplementation trial (PMID:12816783), the fulvic-acid mechanism (PMID:10090708), hand X-ray screening signs (PMID:29459762), the ADAM12 GWAS (PMID:27545300), the primary rat-model papers (PMID:22258458, PMID:22294316, PMID:23701828), TSG-6 (PMID:36468025), GPx6 (PMID:42384133), mitochondrial function (PMID:20650322), the 2001 histology (PMID:11482529), the causality review (PMID:11482536), and the burden, quality-of-life, depression and sarcopenia literature. Only caches this entry cites are committed. Negative results are first-class here. 9 REFUTE items and 1 NO_EVIDENCE item are curated alongside the positive evidence, including the rat model explicitly failing to reproduce the human growth-plate lesion (recorded as a FAILS_TO_RECAPITULATE model link with an INVALIDATING SPECIES_MISMATCH divergence), the randomised trial finding selenium useless for established disease once iodine was corrected, and the network meta-analysis reporting vitamin C and aspirin as both effective and not established. Validation. `just validate-disorders` passes with all snippets verified against committed caches; `validate-terms`, `check-duplicate-keys`, `check-enum-values`, `check-entity-refs`, `check-causal-targets`, `check-qualifier-terms`, `check-folded-hyphens`, `check-snippet-length`, `check-title-snippets`, `check-snippet-grading`, `check-empty-snippets`, `check-reference-titles` and `check-environmental-evidence` all pass. Pathograph audited: 4 roots, no orphans, no unresolved bare-name targets.

Claude Code ▸

Kashin-Beck Disease: Comprehensive Research Report

claude-haiku-4-5-20251001, claude-sonnet-5 71 citations 2026-09-07T14:10:34.198951

Kashin-Beck Disease: Comprehensive Research Report

1. Disease Information

Overview. Kashin-Beck disease (KBD) is a chronic, endemic osteochondropathy — a degenerative, non-inflammatory disorder of growth-plate and articular cartilage — that produces symmetric joint enlargement, growth retardation, and in severe cases dwarfism. It is confined to a specific geographic belt and is considered a multifactorial environmental disease rather than a Mendelian genetic disorder, though genetic susceptibility loci have been identified. Onset is characteristically in childhood (ages 3–13), with progressive, largely irreversible skeletal changes ("Pathophysiological drivers include environmental toxins such as T-2 mycotoxin, nutritional deficiencies (notably selenium and iodine), and genetic predispositions that converge on dysregulated signalling pathways" — Nature Index summary).

Key identifiers: - MONDO: MONDO:0005610 — classified as a subclass of osteochondrodysplasia (Monarch Initiative) - ICD-11: FA27.0 - ICD-10: M12.1 (Kaschin-Beck disease) - ICD-9: 716.0 - OMIM does not carry a dedicated Mendelian entry (KBD is not modeled as single-gene disease in OMIM); Orphanet listing was not confirmed in available searches — verify directly before curation.

Synonyms: Kaschin-Beck disease, Kashin–Bek disease, "Big Bone Disease" (colloquial/regional), Urov disease (older Russian literature), endemic osteoarthritis, endemic deforming osteoarthrosis, endemic osteochondropathy.

Data source note. Virtually all available evidence is aggregated disease-level/epidemiological and mechanistic literature (national surveillance reports, cross-sectional and cohort studies, case series, animal-model and omics studies) rather than individual EHR-level records — consistent with KBD's status as a public-health/endemic-disease research area concentrated in Chinese, Tibetan, and Russian populations.

Sources: ScienceDirect overview, Wikidata, Monarch Initiative MONDO:0005610

2. Etiology

KBD etiology is unresolved and actively debated; four historical hypotheses persist in the literature, now generally synthesized into a "compound etiology" model:

Selenium (Se) deficiency hypothesis (biogeochemical) — endemic regions overlap low-Se soil/food belts (shared with Keshan disease).
Mycotoxin hypothesis — grain (wheat/corn) stored under damp conditions becomes contaminated with Fusarium fungi producing T-2 toxin and other trichothecene mycotoxins.
Organic water-pollution/humic-fulvic acid hypothesis — high humic/fulvic acid content in local drinking water, generating free radicals via oxy/hydroxy functional groups that damage chondrocyte membranes and increase lipid peroxidation (PubMed 10090708; Springer PMC3620638).
Compound/multifactorial etiology — current consensus, integrating Se deficiency, T-2 toxin exposure, iodine deficiency, and genetic susceptibility as converging, synergistic factors rather than a single monocausal agent (ScienceDirect animal models review).

"Four etiological hypotheses have been formed, including water of organic poisoning hypothesis represented by fulvic acid (FA), biogeochemical hypothesis represented by selenium (Se) deficiency, food mycotoxin poisoning hypothesis represented by T-2 toxin poisoning and compound etiology theory hypothesis." — Animal models of KBD, ScienceDirect 2022

Genetic Risk Factors

ADAM12 — a bivariate GWAS (2,417 subjects, phenotypes = joint deformity + body height) found the top signal at rs1278300 (p = 9.25×10⁻⁹), replicated at rs1278300 (p=0.007) and rs1710287 (p=0.002); ADAM12 protein expression was significantly reduced in KBD articular cartilage by immunohistochemistry (PMC4992896; Sci Rep).
COL10A1, HABP2 — coding-region sequencing in Tibetan populations identified candidate susceptibility variants (BMC Med Genet).
Selenoprotein gene polymorphisms (e.g., GPX1, SEPP1 family) associated with KBD risk and serum Se/iodine levels in Tibetan populations (PMC3751926).
GDF5 and DIO2 — bone-development genes implicated preferentially in pediatric-onset (vs adult) KBD by gene expression analysis (PMC4114804); DIO2 encodes selenium-dependent type 2 deiodinase, mechanistically linking thyroid hormone activation to Se status.

Environmental Risk Factors

Low soil/dietary selenium (shared biogeochemical belt with Keshan disease, a cardiomyopathy).
Grain (cereal) contamination with Fusarium-derived T-2 mycotoxin, especially in humid storage conditions.
Humic/fulvic-acid-rich drinking water.
Concurrent iodine deficiency, which appears to potentiate risk in severely Se-deficient areas ("In areas where severe selenium deficiency is endemic, iodine deficiency is a risk factor for Kashin-Beck disease" — ScienceDirect).
Cold climate/seasonality has been proposed as a contributing modifier (De Gruyter, "Cold weather and Kashin-Beck disease," 2023).
Age (childhood exposure window is critical) and rural/subsistence-agriculture lifestyle (dependence on locally grown grain and untreated well water).

Protective Factors

Adequate dietary/serum selenium (confirmed protective across multiple RCTs and ecological studies).
Higher dietary protein intake — "certain combinations of food substances high in protein had a protective effect" (PMC8999107).
Grain replacement (importing Se-adequate, non-locally-grown, non-fungally-contaminated grain) — a core public-health intervention, not merely a research finding.
Improved drinking-water sourcing (piped/treated water displacing local humic-acid-rich wells).

Gene-Environment Interaction

Selenoprotein genotype modulates individual susceptibility to a shared environmental (low-Se, high T-2 toxin) exposure — e.g., selenoprotein gene polymorphism studies show genotype-dependent serum Se/iodine associations with KBD risk in the same geographic cohort (PMC3751926). Recent work also frames KBD as a sarcopenia risk factor whose severity interacts with selenium status ("Kashin–Beck Disease: A Risk Factor for Sarcopenia and Its Interaction with Selenium" — PMC11678709).

3. Phenotypes

Clinical/Physical Manifestations

Arthralgia and morning stiffness (early symptom)
Symmetric joint enlargement — particularly finger interphalangeal/metacarpophalangeal joints, wrists, ankles, knees, elbows
Shortened fingers/brachydactyly — from premature epiphyseal closure
Restricted range of motion / joint stiffness
Genu varum/valgum and other limb deformities
Growth retardation → short stature → dwarfism in severe cases
Muscle atrophy adjacent to affected joints (secondary)
Sarcopenia as a later-life comorbidity/consequence (PMC11678709)

Suggested HP terms: HP:0002829 (Arthralgia), HP:0001367 (Abnormal joint morphology), HP:0002652 (Skeletal dysplasia), HP:0011800 (Midface retrusion — N/A, omit), HP:0001773 (Short foot), HP:0100729 (Large joint involvement — verify exact term), HP:0002980 (Joint stiffness/limitation of joint mobility — HP:0001376), HP:0004322 (Short stature), HP:0009824 (Osteolysis — not typical, avoid), HP:0002751 (Kyphoscoliosis — occasional secondary), HP:0001156 (Brachydactyly).

Behavioral/Psychological

Depression and anxiety are elevated in KBD patients relative to the general population; a 2025 study specifically examined prevalence and risk factors of depression in KBD (PMC12440642).
Reported psychosocial burden: "strong sense of inferiority compared with their peers," financial difficulty, restricted activity (PMC10161486).

Laboratory Abnormalities

Low serum/urinary selenium and zinc, especially in children in endemic areas, tracked longitudinally (PMC9033266)
Altered serum metabolomic profile: candidate biomarkers include kynurenic acid, N-α-acetylarginine, 6-hydroxymelatonin, sphinganine, ceramide, sphingosine-1-phosphate, spermidine, and glycine (ScienceDirect)
Altered fecal metabolome reflecting disturbed selenium-centered metabolic bioprocesses (PMC10650499)
Gut microbiota dysbiosis: elevated Fusobacteria and Bacteroidetes; enriched Alloprevotella, Robinsoniella, Megamonas, Escherichia-Shigella (Cell Death & Disease / PMC8553765)

Onset, Severity, Progression

Onset: Predominantly childhood, ages 3–13 (some sources report 5–15); clinical deformity can appear by age 5 or earlier.
Severity/staging (Chinese national clinical grading, three grades):
Grade I: enlarged finger joints, limited range of motion, limb-joint pain
Grade II: shortened fingers + Grade I features
Grade III: dwarfism + Grade II features ("stage I KBD is defined as enlarged finger joints, limited range of motion and pain... stage II as shortened fingers... stage III as dwarfism" — search synthesis of academic.oup.com/rheumatology and related sources)
Progression: chronic, largely irreversible once epiphyseal/growth-plate damage occurs; adult disease resembles accelerated, severe generalized osteoarthritis.
Frequency: National X-ray detectable rate fell from 21.01% (1990) to <10% (2003), <5% (2007), <0.4% in children (2010–2018), and 0% since 2019 per Chinese national surveillance (BES Journal), though Tibet remains an active transmission area with occasional new cases.

Quality of Life

HRQoL is lower in KBD than in ordinary osteoarthritis patients across physical function, activity limitation, mental health, and general health domains (PMC10161486; EQ-5D study).
Most affected EQ-5D dimension: pain/discomfort, followed by mobility, anxiety/depression, usual activities, self-care.
Severe (Grade II/III) and older (≥60y) patients show the largest healthy-life-expectancy losses, with substantial indirect economic burden (112.74 million CNY reported in one 2021 national burden analysis — PubMed 38250701).

4. Genetic/Molecular Information

KBD is not a single-gene Mendelian disorder; it is a gene–environment disease with polygenic susceptibility contributions.

Causal/susceptibility genes: ADAM12 (hgnc:188) — strongest GWAS hit, reduced protein expression in cartilage (PMC4992896); GDF5, DIO2 (pediatric-predominant expression signature — PMC4114804); COL10A1, HABP2 (candidate coding variants, Tibetan cohort); selenoprotein pathway genes.
Variant classification: No ClinVar pathogenic/likely-pathogenic single-variant entries identified for KBD in these searches — susceptibility-variant framework (GWAS SNP associations), not ACMG/AMP monogenic classification.
Functional consequences: Predominantly loss-of-expression/regulatory effects (e.g., decreased ADAM12 protein in affected cartilage) rather than classic LOF/GOF coding mutations.
Epigenetics: Not deeply characterized in the literature surfaced; no dedicated DNA-methylation/ChIP dataset for KBD identified — flag as a knowledge gap.
Molecular/transcriptomic findings:
ADAM12 downregulation in cartilage.
WISP1 (Wnt-inducible signaling pathway protein 1) overexpressed in KBD chondrocytes, modulating autophagy markers ATG4C and LC3-II and ECM synthesis (MDPI 2023; PMC10671535).
GPx6 downregulation drives ferroptosis via the SLC7A11/GPx4 axis, with decreased COL2A1/ACAN and increased MMP13/ADAMTS4 (Apoptosis journal 2026; PMC13323611).
SIRT3 and primary cilia integrity implicated; magnetofection-delivered SIRT3-targeting siRNA ameliorates cartilage damage in a rat model (Theranostics/PMC13440625).
RUNX2 overexpression (selenium-mediated) and associated transcriptome alterations linked to chondrocyte injury (PMC12714888).
TSG-6 abnormal expression disturbs ECM homeostasis (PMC9715581).
Zip6 (SLC39A6) zinc transporter expression modulated by Se/T-2 toxin status, implicating Zn²⁺ dysregulation (PubMed 39455492).
p-ATF2 via JNK/p38 MAPK signaling drives chondrocyte apoptosis (PMC3726291).
Chromosomal abnormalities: None reported — KBD is not associated with aneuploidy/structural chromosomal rearrangement.

Suggested GO/molecular annotations: GO:0006915 (apoptotic process), GO:0034599 (cellular response to oxidative stress), GO:0006914 (autophagy), GO:0097707 (ferroptosis — if available as GO term/verify current OBO status), GO:0030198 (extracellular matrix organization), GO:0007179 (TGF-beta receptor signaling), GO:0060070 (canonical Wnt signaling pathway), GO:0038066 (p38MAPK cascade).

5. Environmental Information

Toxins/exposures: T-2 toxin (trichothecene mycotoxin from Fusarium spp. contaminating stored grain) — chondrocyte-toxic, elevates apoptotic proteins Fas, p53, Bax while decreasing anti-apoptotic Bcl-xL. Fluorine co-exposure impairs carboxylesterase 1-mediated T-2 toxin hydrolysis, increasing its chondrotoxicity (PMC9381868) — a notable toxin-toxin interaction.
Water contaminant: humic/fulvic acid in drinking water (free-radical generation, lipid peroxidation of chondrocyte membranes).
Lifestyle/dietary factors: subsistence agriculture with locally grown, Se-poor, potentially fungally-contaminated grain as primary caloric source; low dietary protein; reliance on untreated local well water.
Infectious agents: None — KBD is not infectious; the "fungal" association is toxicological (mycotoxin contamination of stored food), not an active infection of the host.
Suggested ECTO terms: exposure to T-2 toxin via ingestion; exposure to humic/fulvic acid via drinking water; dietary selenium deficiency exposure.

6. Mechanism / Pathophysiology

Causal chain (ordered, with inference flags)

Chronic environmental exposure — low dietary/soil selenium plus ingestion of T-2 mycotoxin-contaminated grain (and, in some regions, humic/fulvic-acid-rich drinking water) — leads to systemic selenium deficiency and direct mycotoxin/oxidant burden in growth-plate and articular chondrocytes. (Demonstrated ecologically and in animal models; the relative causal weight of each co-factor is still debated — inferred compound mechanism.)
Selenium deficiency results in reduced activity of selenoenzymes (glutathione peroxidases, including GPx6, and thioredoxin reductase), which leads to impaired antioxidant defense and accumulation of reactive oxygen species (ROS) in chondrocytes.
T-2 toxin (potentiated by co-exposures such as fluorine, which impairs its detoxifying hydrolysis) directly triggers oxidative stress, mitochondrial dysfunction, and disrupted AMPK/mTOR/ULK1-mediated autophagy signaling in chondrocytes (ScienceDirect 2024).
Combined oxidative stress and autophagy dysregulation activate multiple regulated chondrocyte death pathways in parallel (branch point):
Apoptosis — via JNK/p38 MAPK → ATF2/p-ATF2 signaling and mitochondrial Fas/p53/Bax-Bcl-xL imbalance (PMC3726291; PMC10467099).
Necroptosis — RIP3-dependent, predominating in the middle zone of cartilage in pediatric KBD samples, distinct from TUNEL/caspase-3-associated classic apoptosis (PMC6384500).
Ferroptosis — GPx6 downregulation disinhibits lipid peroxidation via the SLC7A11/GPx4 axis, producing characteristic mitochondrial cristae loss and matrix vacuolization, concentrated in the deep zone (Apoptosis 2026).
Dysregulated WISP1/Wnt–β-catenin signaling and TGF-β/Smad3 pathways further impair normal chondrocyte matrix-synthesis programs and autophagic flux (ATG4C, LC3-II), compounding the death signal (PMC10671535).
Widespread chondrocyte death (necrosis/apoptosis/necroptosis/ferroptosis acting in different cartilage zones) causes focal chondronecrosis, most pronounced in the deep zone of growth-plate and articular cartilage, accompanied by loss of ECM components — decreased type II collagen (COL2A1) and aggrecan (ACAN), and increased matrix-degrading enzymes MMP13 and ADAMTS4 (PMC13323611).
Progressive chondronecrosis and ECM degradation at the growth plate lead to disordered endochondral ossification: irregular epiphyseal/metaphyseal mineralization, premature epiphyseal-line closure, and cone-shaped epiphyses on imaging.
Disordered growth-plate ossification results in growth-plate arrest and asymmetric longitudinal bone growth, manifesting clinically as shortened fingers/limbs and, in severe cases, dwarfism.
In parallel, chondronecrosis and ECM loss in articular (non-growth-plate) cartilage lead to secondary degenerative joint changes indistinguishable in later life from severe generalized osteoarthritis — joint-space narrowing, osteophyte formation, joint enlargement, and pain.
Chronic joint pain, deformity, and restricted mobility culminate in functional disability, sarcopenia, reduced health-related quality of life, and elevated rates of depression/anxiety (downstream systemic/psychosocial consequence, well-documented but several inferential steps removed from the initiating molecular lesion).

Detail by category

Molecular pathways: p38 MAPK, JNK, TGF-β/Smad3, Wnt/β-catenin (via WISP1), AMPK/mTOR/ULK1 (autophagy), SLC7A11/GPx4 (ferroptosis axis).
Cellular processes: apoptosis, necroptosis, ferroptosis, autophagy dysregulation, oxidative stress, mitochondrial dysfunction (altered mitochondrial density/cristae — PubMed 20650322).
Protein dysfunction: loss of ADAM12 and GPx6 expression; TSG-6 dysregulation; RUNX2 overexpression; SIRT3 loss affecting primary cilia.
Metabolic changes: disturbed selenium-centered metabolic bioprocesses (fecal/serum metabolomics), altered lipid metabolism (unsaturated fatty acids, glycerophospholipids), disordered glycometabolism (ScienceDirect).
Immune involvement: Not a classical autoimmune/inflammatory arthropathy; gut microbiota alterations are proposed to influence chondrocyte injury via inflammatory-mediator signaling, but this is an emerging/inferred link rather than an established primary immune mechanism (PMC8553765).
Tissue damage mechanisms: oxidative stress and lipid peroxidation (both Se-deficiency- and fulvic-acid-driven), chondronecrosis, cartilage matrix degeneration.
Molecular profiling: transcriptomic (RUNX2 pathway study), metabolomic (serum + fecal), microbiome (16S/metagenomic) — no large-scale single-cell/spatial-transcriptomic KBD dataset was identified in this search; flag as a data gap, though "recent insights into chondrocyte heterogeneity reveal expansion of mitochondrial-rich and homeostatic subpopulations in affected cartilage" was referenced in a synthesis source (verify primary citation before using).

Suggested GO terms for pathophysiology nodes: GO:0006915 (apoptotic process), GO:0070266 (necroptotic process), GO:0060670 or emerging ferroptosis GO term (verify current OBO Foundry status for "ferroptosis"), GO:0016239 (positive regulation of macroautophagy), GO:0030199 (collagen fibril organization), GO:0022617 (extracellular matrix disassembly). Suggested CL terms: CL:0000138 (chondrocyte), CL:1001606 or CL:0000743 (growth plate chondrocyte context — verify exact CL binding), CL:0000605 (articular chondrocyte, if resolvable).

7. Anatomical Structures Affected

Organ level: Skeletal system — primary target is cartilage (growth-plate/epiphyseal and articular). Secondary/complication-level involvement: skeletal muscle (sarcopenia), and indirectly the endocrine/thyroid axis (co-occurring iodine deficiency).
Tissue/cell level: Growth-plate (physeal) cartilage and hyaline articular cartilage; chondrocytes are the principal affected cell type (CL:0000138), with zone-specific vulnerability — deep zone predominates for chondronecrosis/ferroptosis, middle zone for necroptosis.
Subcellular level: Mitochondria (dysfunction, cristae loss — GO:0005739), lysosome/autophagosome machinery (ATG4C, LC3-II), primary cilium (SIRT3-dependent).
Localization (UBERON): Most affected joints — interphalangeal and metacarpophalangeal joints of the hand, wrist, elbow, knee, and ankle. UBERON candidates: UBERON:0001981 (growth plate cartilage — verify exact ID), UBERON:0001415 (interphalangeal joint), UBERON:0001465 (knee joint), UBERON:0000004 (ankle joint region — verify).
Lateralization: Predominantly bilateral and symmetric joint involvement — a distinguishing clinical feature from unilateral post-traumatic osteoarthritis.

8. Temporal Development

Onset: Childhood, typically ages 3–13 (some sources cite 5–15); insidious onset with early symptoms of joint pain/enlargement, often first evident in finger joints by age 5.
Progression: Chronic and largely irreversible once epiphyseal damage has occurred; disease severity is staged I→II→III as described above (§3). Progression from finger-joint enlargement (Grade I) to shortened digits (Grade II) to dwarfism (Grade III) reflects cumulative growth-plate injury during the pediatric growth window.
Disease course pattern: Progressive during the pediatric exposure window; in adulthood the residual skeletal deformity is generally stable structurally, but articular cartilage continues to degenerate as a secondary osteoarthritis-like process, so functional/pain burden can still worsen with age.
Critical period: Childhood (particularly early childhood through puberty, while growth plates remain open) is the critical vulnerability window — once growth plates fuse, new KBD-type growth-plate lesions cannot occur, though secondary joint degeneration continues.
Remission: No spontaneous remission; selenium/grain-replacement intervention during the pediatric window can halt or reduce further metaphyseal lesion progression (radiographically demonstrated) but does not reverse established deformity.

9. Inheritance and Population

Epidemiology: Historically affected a large population across a crescent-shaped endemic belt from northeastern China through central China to Tibet, and into Siberia, Mongolia, and North Korea. As of 2018 Chinese Ministry of Health statistics, 535,878 individuals were affected across 379 counties in 13 provinces/autonomous regions. National X-ray-detectable rate in children fell from 21.01% (1990) to <10% (2003), <5% (2007), <0.4% (2010–2018), and reportedly 0% since 2019, with elimination-standard achievement reported in all monitored villages over the most recent 5-year evaluation period (BES Journal 2024). Tibet (e.g., Qamdo, Luolong County) remains an area of ongoing, if low-level, active transmission with occasional new clinical cases.
Inheritance pattern: Not Mendelian — polygenic/multifactorial susceptibility (GWAS-identified risk alleles such as ADAM12 rs1278300) interacting with environmental exposure; no simple AD/AR/X-linked pattern applies.
Penetrance/expressivity: Variable, environmentally gated — genetic susceptibility manifests only in the presence of the requisite low-Se/high-mycotoxin environmental exposure; severity (Grade I–III) is variably expressive.
Founder effects/consanguinity: Not established as relevant given the environmental/polygenic model.
Population demographics: Disproportionately affects rural, subsistence-farming populations, notably ethnic Tibetan and Han populations within the endemic belt; some studies note higher risk in older age and in girls in Tibetan cohorts (OR=1.86), while earlier Chinese cohort data reported roughly 2:1 male excess in some 12-year-old subgroups — sex-ratio findings are inconsistent across studies/regions and should not be over-generalized.
Geographic distribution: Endemic, latitude-band distribution strongly correlated with Se-poor soil geochemistry; recent spatial-epidemiology work has mapped county-level hotspots in Gansu Province and used spatial regression to quantify health loss by county (PubMed 41984302; PubMed 41255597).

10. Diagnostics

Clinical/radiographic criteria: China's national standard is "Diagnostic Criteria for Kashin-Beck Disease" (WS/T 207), most recently updated as WS/T 207-2010 (superseding WS/T 207-2001), combining X-ray pathological signs with clinical manifestations, applied by trained examiners (BES Journal validation study).
Key radiographic (pediatric hand/wrist) signs: large metaphyseal defects with cone-shaped alterations, early epiphyseal-line closure, cone-shaped epiphysis, sclerosis at the metacarpal base, irregular/sclerotic carpal margins (PMC5818476).
Adult ankle X-ray grading: grades 0–IV (grade IV subdivided a–d), benchmarked against Kellgren-Lawrence OA grading; X-ray grade correlates moderately with ankle pain but only weakly with finger-joint clinical grading, underscoring that radiographic and clinical severity are not interchangeable measures (PubMed 41342918).
Emerging computational diagnostics: deep-learning/transfer-learning models for automated metaphyseal-sign detection on pediatric hand X-rays, and graph neural network (GNN)-based auxiliary diagnosis tools (ACM DL 2024; PMC11871940; PubMed 41398140).
Laboratory tests: serum/urinary selenium and zinc levels (surveillance biomarkers, not diagnostic per se); emerging serum/fecal metabolomic biomarker panels (kynurenic acid, sphingolipids, spermidine, etc.) are research-stage, not yet clinical diagnostics.
Genetic testing: Not part of standard clinical diagnosis (KBD is diagnosed clinically/radiographically); GWAS/candidate-gene panels (ADAM12, DIO2, GDF5, selenoprotein genes) are research tools for susceptibility studies, not diagnostic assays.
Differential diagnosis: Primary comparator is idiopathic/generalized osteoarthritis (KBD is distinguished by pediatric onset, symmetric small-joint predominance, growth-plate involvement/short stature, and endemic geographic exposure); rickets and other skeletal dysplasias should be excluded, though this specific comparison was not deeply sourced in this search — flag for direct lookup against UpToDate/DynaMed before finalizing curation.
Screening: Community/school-based radiographic screening programs in endemic counties (part of China's national surveillance system) function as the de facto population screening mechanism; no genetic carrier-screening program applies (non-Mendelian disease).

11. Outcome/Prognosis

Mortality: KBD is not directly life-threatening; no disease-specific mortality data were identified — it is a disabling, non-fatal osteochondropathy.
Morbidity/function: Severe cases (Grade II/III) cause lifelong joint deformity, restricted mobility, and disability; loss of ability to work/self-care is reported in advanced cases ([search synthesis, multiple sources above]).
Complications: Secondary/accelerated osteoarthritis in adulthood; sarcopenia (independent association, modulated by selenium status — PMC11678709 and OARSI 2025); depression/anxiety (PMC12440642).
Quality of life: Substantially reduced versus both healthy controls and ordinary OA patients across EQ-5D and SF-36-type domains, most severely in pain/discomfort and mobility (PMC10161486).
Economic burden: 2021 national burden analysis reported an indirect economic burden of 112.74 million CNY, concentrated in Grade II and ≥60-year-old patients (PubMed 38250701); a 2019-vs-2023 county-level spatial-regression study further quantified "health loss" hotspots (PubMed 41255597).
Prognostic factors: disease grade (II/III much worse than I), age at diagnosis/treatment initiation (earlier selenium intervention preserves more growth-plate function), and residual selenium status.
Recovery potential: Selenium/grain-replacement therapy during the open-growth-plate window can arrest new metaphyseal lesion formation and partially remodel existing lesions radiographically, but established deformity and short stature are not reversible.

12. Treatment

Pharmacotherapy — Selenium supplementation (children/pediatric prevention & treatment): Effective for radiographic structural improvement and repair of metaphyseal lesions; a large network meta-analysis (44 RCTs, 9,815 participants) and a focused NMA (15 RCTs, 2,931 patients comparing 5 selenium-supplement types) both found selenium superior to placebo, though the comparative superiority among selenium formulations remains inconclusive due to evidence quality limits (PubMed 29511006; PubMed 31376086; ResearchGate NMA). Iodine co-supplementation has also been trialed in Tibetan children (PubMed 12816783).
Suggested NCIT term: NCIT:C15986 (Pharmacotherapy), with therapeutic_agent bound to selenium compound (e.g., sodium selenite — CHEBI term to be verified) as agent.
Pharmacotherapy — Adult symptom management: Glucosamine, chondroitin, intra-articular hyaluronic acid (IAH), and NSAIDs are all reported effective for adult symptomatic relief; chondroitin + glucosamine combination ranked best for pain in the same network meta-analysis, followed by IAH, chondroitin, and glucosamine monotherapy versus placebo (PubMed 31376086).
Surgical/interventional: Corrective surgery and joint replacement/arthroplasty for severe deformity; a documented case example is conservative tibiotalocalcaneal fusion for partial talar avascular necrosis with ankle/subtalar osteoarthritis in KBD (PMC6709310). Evidence base for surgical/complementary interventions is noted as still limited/"yet to be established" in systematic review.
Suggested NCIT terms: NCIT:C15329 (Surgical Procedure), NCIT:C16186 (Orthopedic Surgical Procedure).
Supportive/rehabilitative: Physical therapy to maintain mobility and prevent further deformity, pain management, nutritional support.
Suggested NCIT term: NCIT:C15302 (Physical Therapy).
Experimental/preclinical (not yet clinical): siRNA targeting SIRT3 via magnetofection delivery to protect primary cilia and reduce cartilage damage — demonstrated in a rat model, not yet in human trials (Theranostics/PMC13440625); selenomethionine-mediated antagonism of T-2-toxin-induced apoptotic microRNAs, also rat-model stage (PMC10467099).
Treatment strategy: Public-health strategy is explicitly two-pronged — primary prevention via grain replacement/selenium fortification (population level, pediatric-window focus) combined with individual symptomatic/surgical management for already-affected adults; no NCT-numbered active interventional trial registry entries were surfaced in this search (most identified RCTs are older, pre-registry-era or indexed only via PubMed/meta-analysis) — verify clinicaltrials.gov directly for any currently active protocol before citing an NCT identifier.

13. Prevention

Primary prevention (most emphasized in the literature): Grain replacement — substituting non-locally-grown, non-fungally-contaminated, Se-adequate grain for local subsistence grain — combined with selenium supplementation programs, is repeatedly identified as the most effective population-level intervention ("Comprehensive measures and change of grain were the most effective measures in preventing new cases" — PMC6738986). Improved/piped drinking water supply is a secondary component targeting the humic-acid pathway.
Public health programs: China's national KBD control program (grain replacement + Se supplementation + water improvement + surveillance) has driven the detectable-rate decline from >20% to ~0% in children since 2019, with formal "elimination standard" achieved across monitored villages in the most recent 5-year evaluation (BES Journal 2024).
Secondary prevention/screening: School- and community-based radiographic (hand/wrist X-ray) screening in endemic counties for early metaphyseal-lesion detection, enabling earlier selenium intervention during the still-open growth-plate window.
Tertiary prevention: Ongoing selenium/nutritional maintenance plus symptomatic/surgical management to limit progression of secondary osteoarthritis and disability in already-affected individuals.
Genetic/counseling interventions: Not applicable — KBD is environmentally driven; no prenatal or carrier-screening framework exists.
Note on residual risk: Despite major national progress, Tibet is repeatedly flagged as an area where the disease remains "relatively active" with occasional new cases, underscoring that grain-replacement/selenium programs require sustained implementation rather than being a one-time fix (PMC7792790; search synthesis above).

14. Other Species / Natural Disease

KBD is essentially a human-specific clinical entity in the epidemiological/nosological literature; no naturally occurring veterinary counterpart with the identical name was identified in this search (searches for a livestock/equine "big bone disease" analog returned only human-disease sources and general equine selenium-deficiency nutrition references, e.g., Merck Veterinary Manual). Colloquially "Big Bone Disease" is sometimes used as a lay synonym for KBD itself, not a distinct veterinary disease.
Relevant comparative pathology: Selenium-deficiency osteopathy/osteopathology has been documented in wildlife (e.g., endangered Patagonian huemul deer, Hippocamelus bisulcus — PMC4522092), representing a related but etiologically distinct Se-deficiency skeletal disorder rather than a validated KBD ortholog. This is comparative/analogous evidence, not a direct animal model of KBD.
Model organisms are used experimentally to induce KBD-like pathology (see §15) rather than representing naturally occurring disease.

15. Model Organisms

Rat models (most validated): Selenium-deficient diet (typically 4 weeks) followed by T-2 toxin exposure (typically 4 weeks) reliably reproduces chondronecrosis in the deep zone of knee articular cartilage, closely resembling human KBD histopathology; considered "a suitable animal model for studying etiological factors contributing to the pathogenesis (chondronecrosis) observed in human KBD" (PubMed 22258458; PubMed 22294316; J Orthop Res). A low-nutrition-diet + T-2 toxin variant has also been reported (PubMed 23701828).
Other species tested: Monkey, dog, pig, chicken, and rabbit models have been used with varying environmental-risk-factor interventions (ScienceDirect comparative review). Important negative finding: "rats, chicken and rabbits administrated Se deficiency failed to replicate KBD when selenium deficiency was used alone" — i.e., Se deficiency alone is insufficient; combined Se-deficiency + T-2 toxin exposure is required to recapitulate the phenotype, supporting the compound-etiology model over any single-factor hypothesis.
Model limitations: No model fully replicates the chronic, multi-decade, growth-plate-specific human clinical course (short stature, dwarfism); most models assess acute-to-subacute chondronecrosis rather than the full skeletal growth-retardation phenotype.
Applications: Rat models have been used to study oxidative stress (SOD/GSH-Px depletion, lipid peroxidation), chondrocyte apoptosis (Fas/p53/Bax/Bcl-xL), autophagy pathway involvement (AMPK/mTOR/ULK1), and to test candidate interventions (selenomethionine antagonism of T-2-induced apoptotic microRNAs; SIRT3-targeting siRNA delivery).
Resources: No dedicated public KBD model-organism database was identified; relevant strain/protocol details are documented within primary publications rather than centralized repositories like MGI/RGD (standard rat strains, e.g., Wistar or Sprague-Dawley, are used under custom dietary/toxin protocols rather than genetically engineered KBD-specific lines).

Summary of Key Ontology Term Suggestions for KB Curation

Category	Suggested term(s)	Notes
Disease	MONDO:0005610	Confirm via direct MONDO lookup
Causal gene (susceptibility)	HGNC ADAM12 (hgnc:188, verify), DIO2, GDF5, COL10A1	Susceptibility, not monogenic-causal
Cell type	CL:0000138 (chondrocyte)	Zone-specific subtypes need verification
Biological process	GO:0006915 (apoptosis), GO:0070266 (necroptosis), GO:0022617 (ECM disassembly), GO:0016239 (autophagy)	Ferroptosis GO term needs current-OBO verification
Anatomy	UBERON terms for growth plate, articular cartilage, interphalangeal/knee/ankle joints	Verify exact IDs before binding
Chemical/exposure	CHEBI for T-2 toxin, selenium/selenite, humic/fulvic acid	ECTO for exposure-route terms
Treatment	NCIT:C15986 (Pharmacotherapy) + therapeutic_agent selenium; NCIT:C15329/C16186 (Surgical); NCIT:C15302 (Physical Therapy)
Phenotype	HP terms for arthralgia, joint enlargement, brachydactyly, short stature, joint stiffness	Full HPO cross-check recommended before final binding

Sources

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	54
Resolved	51
Unresolved (possible confabulation)	3
Unverifiable	0
Quoted claims checked	6
Quoted claims found in source	2
Quoted claims not found in source	4
References weighed for topical relevance	51
On topic	25
Off topic	0

Unresolved references

These identifiers did not resolve to a record and may be fabricated. A lookup that failed for transport reasons is indistinguishable from one that failed because the record does not exist, so spot-check before acting on them:

DOI:10.3967/bes2024.109 (5 mentions) - Identifier did not resolve to a record
DOI:10.3967/bes2017.021 (3 mentions) - Identifier did not resolve to a record
DOI:10.3967/bes2017.046 (2 mentions) - Identifier did not resolve to a record

Quotes not found in the cited source

Searched the abstract, any retrieved full text, and the title. A quote drawn from a part of the paper that was not retrieved will appear here too, so check before treating one as invented:

Every one of these was searched against an abstract alone, with no full text retrieved - marked abstract only below. Where full text can be fetched, re-running with it will settle them; where the source publishes only a summary to PubMed, as GeneReviews chapters do, it will not, and the quote has to be checked by hand against the chapter itself.

PMC:PMC8999107 (abstract only): "certain combinations of food substances high in protein had a protective effect"
Text part not found as substring: 'certain combinations of food substances high in protein had a protective effect' (note: only abstract available for PMID:35419096, full text may contain this excerpt)
PMC:PMC6738986 (abstract only): "Comprehensive measures and change of grain were the most effective measures in preventing new cases"
closest text in source: "CONCLUSION: Comprehensive measures and change of grain were the most effective measures in preventing new case, whereas improvement of water and salt-rich selenium resulted in clinical improvements in children KBD."
PMID:22294316 (abstract only): "a suitable animal model for studying etiological factors contributing to the pathogenesis (chondronecrosis) observed in human KBD"
closest text in source: "These changes were similar to those observed previously in KBD"
DOI:10.1002/jor.22073 (abstract only): "a suitable animal model for studying etiological factors contributing to the pathogenesis (chondronecrosis) observed in human KBD"
closest text in source: "These changes were similar to those observed previously in KBD"

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Outcome	Count
Terms checked	39
Resolved	39
Unresolved (possible confabulation)	0
Obsolete	0
Unverifiable	0
Terms whose name was checked	34
Terms named correctly	21
Terms named as a different term	9
Terms whose name is worth a second look	4

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

MONDO:0005610 (8 mentions) - the report calls it "classified as a subclass of osteochondrodysplasia", "Disease"; MONDO calls it Kashin-Beck disease
HP:0100729 (1 mention) - the report calls it "Large joint involvement — verify exact term"; HP calls it Large face
HP:0009824 (1 mention) - the report calls it "Osteolysis — not typical, avoid"; HP calls it Upper limb undergrowth
GO:0097707 (1 mention) - the report calls it "ferroptosis — if available as GO term/verify current OBO status"; GO calls it ferroptosis
CL:0000743 (1 mention) - the report calls it "growth plate chondrocyte context — verify exact CL binding"; CL calls it hypertrophic chondrocyte
CL:0000605 (1 mention) - the report calls it "articular chondrocyte, if resolvable"; CL calls it fungal asexual spore
UBERON:0001981 (1 mention) - the report calls it "growth plate cartilage — verify exact ID"; UBERON calls it blood vessel
UBERON:0001415 (1 mention) - the report calls it "interphalangeal joint"; UBERON calls it skin of pelvis
UBERON:0000004 (1 mention) - the report calls it "ankle joint region — verify"; UBERON calls it nose

Terms whose name is worth a second look

The report's name for these is recognisably related to the term's own name without being one of them. A loose paraphrase reads the same way as a citation of the wrong sibling term - and so does a related synonym, which the ontology records precisely because it names something adjacent rather than the same thing - so these are listed rather than judged:

HP:0011800 (1 mention) - the report calls it "Midface retrusion — N/A, omit"; HP calls it Midface retrusion
HP:0002751 (1 mention) - the report calls it "Kyphoscoliosis — occasional secondary"; HP calls it Kyphoscoliosis
GO:0007179 (1 mention) - the report calls it "TGF-beta receptor signaling"; GO calls it transforming growth factor beta receptor signaling pathway, and lists "TGF-beta receptor signaling pathway" among its other names
UBERON:0001465 (1 mention) - the report calls it "knee joint"; UBERON calls it knee, and lists "knee region" among its other names

Terms named inconsistently

The report gives these identifiers more than one name of its own:

MONDO:0005610 - called "classified as a subclass of osteochondrodysplasia", "Disease"

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Pathophysiology

Histopathology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Environmental Factors

Biochemical Markers

Diagnosis

Progression

Prevalence

Epidemiology

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Related Datasets

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References & Deep Research

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Kashin-Beck Disease: Comprehensive Research Report

1. Disease Information

2. Etiology

Genetic Risk Factors

Environmental Risk Factors

Protective Factors

Gene-Environment Interaction

3. Phenotypes

Clinical/Physical Manifestations

Behavioral/Psychological

Laboratory Abnormalities

Onset, Severity, Progression

Quality of Life

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

Causal chain (ordered, with inference flags)

Detail by category

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Summary of Key Ontology Term Suggestions for KB Curation

Sources

Reference Validation

Unresolved references

Quotes not found in the cited source

Term Validation

Terms the report names something else

Terms whose name is worth a second look

Terms named inconsistently