Diastrophic dysplasia (DTD) is an autosomal recessive skeletal dysplasia caused by biallelic pathogenic variants in SLC26A2, encoding a sulfate/chloride antiporter essential for sulfate uptake in chondrocytes. Deficient sulfate transport leads to undersulfation of cartilage proteoglycans, disrupting extracellular matrix composition and impairing endochondral ossification. Secondary consequences include collagen retention in the endoplasmic reticulum, activation of the unfolded protein response, and pathogenic overactivation of FGFR3 signaling. The phenotype comprises disproportionate short-limbed short stature, joint contractures, spinal deformities, hitchhiker thumbs, clubfoot, cleft palate, and cystic swelling of the external ear. Intelligence is normal. Severity correlates with residual SLC26A2 activity.
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name: Diastrophic Dysplasia
creation_date: '2026-03-04T07:00:00Z'
updated_date: '2026-04-19T00:08:54Z'
category: Mendelian
classifications:
harrisons_chapter:
- classification_value: musculoskeletal system disorder
- classification_value: hereditary disease
description: >
Diastrophic dysplasia (DTD) is an autosomal recessive skeletal dysplasia caused
by biallelic pathogenic variants in SLC26A2, encoding a sulfate/chloride
antiporter essential for sulfate uptake in chondrocytes. Deficient sulfate
transport leads to undersulfation of cartilage proteoglycans, disrupting
extracellular matrix composition and impairing endochondral ossification.
Secondary consequences include collagen retention in the endoplasmic reticulum,
activation of the unfolded protein response, and pathogenic overactivation of
FGFR3 signaling. The phenotype comprises disproportionate short-limbed short
stature, joint contractures, spinal deformities, hitchhiker thumbs, clubfoot,
cleft palate, and cystic swelling of the external ear. Intelligence is normal.
Severity correlates with residual SLC26A2 activity.
disease_term:
preferred_term: diastrophic dysplasia
term:
id: MONDO:0009107
label: diastrophic dysplasia
parents:
- Skeletal Dysplasia
inheritance:
- name: Autosomal Recessive
description: >
Diastrophic dysplasia is inherited in an autosomal recessive pattern.
Heterozygous carriers of SLC26A2 pathogenic variants are asymptomatic.
evidence:
- reference: PMID:24598000
reference_title: "SLC26A2 disease spectrum in Sweden - high frequency of recessive multiple epiphyseal dysplasia (rMED)."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Diastrophic dysplasia (DTD) is an autosomal recessive skeletal dysplasia
caused by SLC26A2 mutations.
explanation: >-
This cohort report directly states recessive inheritance and SLC26A2
causality.
prevalence:
- population: Live births (worldwide)
percentage: 1 in 100,000 live births
notes: >-
Estimated incidence of approximately 1 in 100,000 live births in
non-Finnish populations. Historically much higher in Finland (~1:22,000)
due to a founder mutation, though Finnish incidence has decreased with
improved prenatal diagnostics.
evidence:
- reference: PMID:23657516
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Diastrophic dysplasia is a type of osteochondrodysplasia caused by
homozygous mutation in the gene DTDST (diastrophic dysplasia sulfate
transporter gene). Abnormalities occurring particularly in the skeletal
and cartilaginous system are typical of the disease, which has an
incidence of 1 in 100,000 live births.
explanation: >-
This review gives a direct live-birth incidence estimate for diastrophic
dysplasia.
- reference: PMID:10482955
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Diastrophic dysplasia (DTD) is especially prevalent in Finland and the
existence of a founder mutation has been previously inferred from the
fact that 95% of Finnish DTD chromosomes have a rare ancestral haplotype
found in only 4% of Finnish control chromosomes.
explanation: >-
This genetic epidemiology study supports the founder-effect enrichment of
DTD in Finland.
- population: Finland (2000-2020)
notes: >-
The incidence of DTD in Finland has decreased significantly in recent
decades, from approximately 1:22,000 historically to far fewer cases per
year, likely due to improved prenatal diagnostics and genetic counseling.
evidence:
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The incidence of DTD in Finland has significantly decreased over the
past decades, most likely due to increased prenatal diagnostics.
explanation: >-
Registry-based Finnish pediatric cohort showing declining incidence of
DTD attributable to prenatal diagnosis.
progression:
- phase: Prenatal Onset
evidence:
- reference: PMID:3065771
reference_title: "Diastrophic dysplasia: a specific prenatal diagnosis by ultrasound."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The reported case was diagnosed due to evidence of an extreme shortening
of all long bones of the extremities associated with other skeletal
deformities which, taken as a whole, are typical of this syndrome:
micrognathia, cervical kyphosis, persistent extension limitation in elbow
and knee joints, club feet, ulnar diviation of hands, shortened phalanges,
and, in particular, abduction of thumbs ('hitchhiker thumbs') and big
toes.
explanation: >-
Prenatal ultrasound detection of the full DTD skeletal phenotype confirms
in utero onset of disease manifestations.
- phase: Progressive Growth Failure
age_range: Childhood through adolescence
evidence:
- reference: PMID:9108864
reference_title: "Growth in diastrophic dysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The median adult height was 135.7 cm for the male and 129.0 cm for the
female subjects. The growth failure was progressive partly because of
absent or weak pubertal growth spurt.
explanation: >-
Largest growth study of DTD (121 Finnish patients) documenting
progressive growth failure and adult height range.
- phase: Early-Onset Joint Degeneration
age_range: Adolescence to early adulthood
evidence:
- reference: PMID:9546468
reference_title: "Development of the hip in diastrophic dysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The changes in the hip led to secondary osteoarthritis before early
middle age.
explanation: >-
Longitudinal hip radiography study of 50 DTD patients documenting
progressive hip deformity leading to secondary osteoarthritis.
- reference: PMID:14630837
reference_title: "Total knee arthroplasty in patients with diastrophic dysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Diastrophic dysplasia results in severe disproportionate short stature,
generalized joint deformities, and early osteoarthritis. The knee joint
often has an abnormal valgus position and is unstable, and degeneration
of all joint compartments occurs, even during growth.
explanation: >-
Clinical series documenting early-onset knee osteoarthritis requiring
total knee arthroplasty in DTD patients.
pathophysiology:
- name: Sulfate Transport Defect in Cartilage
description: >
Loss of SLC26A2 transporter activity reduces intracellular sulfate in
chondrocytes, osteoblasts, and fibroblasts, causing undersulfation of
cartilage proteoglycans and altering extracellular matrix composition.
Proteoglycans bearing glycosaminoglycan chains that are poorly sulfated
but of normal length cannot maintain proper matrix hydration and
mechanical properties.
genes:
- preferred_term: SLC26A2
term:
id: hgnc:10994
label: SLC26A2
molecular_functions:
- preferred_term: sulfate transmembrane transporter activity
term:
id: GO:0015116
label: sulfate transmembrane transporter activity
cell_types:
- preferred_term: Chondrocyte
term:
id: CL:0000138
label: chondrocyte
- preferred_term: Osteoblast
term:
id: CL:0000062
label: osteoblast
biological_processes:
- preferred_term: Sulfate Transmembrane Transport
term:
id: GO:1902358
label: sulfate transmembrane transport
modifier: DECREASED
- preferred_term: Extracellular Matrix Organization
term:
id: GO:0030198
label: extracellular matrix organization
modifier: ABNORMAL
downstream:
- target: Impaired Endochondral Ossification
causal_link_type: DIRECT
description: >-
Undersulfated proteoglycans disrupt growth plate matrix, impairing
endochondral bone formation.
evidence:
- reference: PMID:22556422
reference_title: "Matrix disruptions, growth, and degradation of cartilage with impaired sulfation."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
undersulfation of dtd was mild in most regions, but strong in narrow
articular and growth plate regions crucial for bone development.
explanation: >-
Regional concentration of undersulfation in growth plate zones
directly links sulfate transport defect to ossification impairment.
- target: Collagen Retention in Endoplasmic Reticulum
causal_link_type: DIRECT
description: >-
SLC26A2 deficiency leads to defective collagen secretion with
intracellular retention of type II and IX collagens.
evidence:
- reference: PMID:30685387
reference_title: "Suppressing UPR-dependent overactivation of FGFR3 signaling ameliorates SLC26A2-deficient chondrodysplasias."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
Unexpectedly, slc26a2-/- chondrocytes are defective for collagen
secretion, exhibiting intracellular retention and compromised
extracellular deposition of ColII and ColIX.
explanation: >-
Collagen retention is a direct consequence of SLC26A2 loss, linking
the sulfate transport defect to ER stress.
evidence:
- reference: PMID:23369989
reference_title: "Alteration of proteoglycan sulfation affects bone growth and remodeling."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
Diastrophic dysplasia (DTD) is a chondrodysplasia caused by mutations in
the SLC26A2 gene, leading to reduced intracellular sulfate pool in
chondrocytes, osteoblasts and fibroblasts.
explanation: >-
Links SLC26A2 dysfunction to sulfate depletion across skeletal
matrix-producing cell types.
- reference: PMID:8702490
reference_title: "Undersulfation of proteoglycans synthesized by chondrocytes from a patient with achondrogenesis type 1B homozygous for an L483P substitution in the diastrophic dysplasia sulfate transporter."
supports: SUPPORT
evidence_source: IN_VITRO
snippet: >-
The results indicate that the defect of sulfate transport is expressed
in both chondrocytes and fibroblasts and results in the synthesis of
proteoglycans bearing glycosaminoglycan chains which are poorly sulfated
but of normal length.
explanation: >-
First biochemical proof that proteoglycan sulfation is deficient in
chondrocytes from patients with SLC26A2 mutations, while GAG chain
length is preserved.
- reference: PMID:22556422
reference_title: "Matrix disruptions, growth, and degradation of cartilage with impaired sulfation."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
undersulfation of dtd was mild in most regions, but strong in narrow
articular and growth plate regions crucial for bone development. This
undersulfation correlated with the chondroitin synthesis rate measured
via radioactive sulfate incorporation
explanation: >-
High-definition infrared imaging of dtd mouse cartilage reveals that
undersulfation is regionally concentrated in the most developmentally
critical zones, explaining why mild overall sulfation deficits produce
severe skeletal consequences.
- name: Impaired Endochondral Ossification
description: >
Defective cartilage matrix quality disrupts growth plate architecture.
The columnar arrangement of proliferative chondrocytes and the transition
to hypertrophic chondrocytes are disordered, with delayed formation of
secondary ossification centers and reduced chondrocyte proliferation,
leading to disproportionate skeletal growth.
cell_types:
- preferred_term: Chondrocyte
term:
id: CL:0000138
label: chondrocyte
biological_processes:
- preferred_term: Endochondral Ossification
term:
id: GO:0001958
label: endochondral ossification
evidence:
- reference: PMID:15703192
reference_title: "A diastrophic dysplasia sulfate transporter (SLC26A2) mutant mouse: morphological and biochemical characterization of the resulting chondrodysplasia phenotype."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
The skeletal phenotype included reduced toluidine blue staining of
cartilage, chondrocytes of irregular size, delay in the formation of the
secondary ossification center and osteoporosis of long bones.
explanation: >-
The dtd knock-in mouse shows growth plate disorganization and delayed
ossification, modeling the human endochondral bone defect.
- reference: PMID:37454964
reference_title: "Identification of potential non-invasive biomarkers in diastrophic dysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Lower than normal CXM levels were observed in most patients, even if
the marker did not show a clear pattern in our small patient cohort
because CXM values are highly dependent on age, gender and growth
velocity.
explanation: >-
Reduced collagen X marker levels in DTD patients indicate impaired
endochondral ossification rate, providing a potential biomarker.
- reference: PMID:22556422
reference_title: "Matrix disruptions, growth, and degradation of cartilage with impaired sulfation."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
Collagen orientation was reduced, and the reduction correlated with
chondroitin undersulfation. Such disorientation involved the layer of
collagen covering the articular surface and protecting cartilage from
degradation.
explanation: >-
Collagen disorientation in the dtd mouse growth plate and articular
surface directly links proteoglycan undersulfation to structural matrix
disruption and progressive cartilage degradation.
- name: Collagen Retention in Endoplasmic Reticulum
description: >
In severe SLC26A2 deficiency, chondrocytes fail to secrete type II
and type IX collagen normally. These collagens accumulate in the
endoplasmic reticulum, causing ER distension and triggering the
unfolded protein response.
cell_types:
- preferred_term: Chondrocyte
term:
id: CL:0000138
label: chondrocyte
biological_processes:
- preferred_term: Response to Endoplasmic Reticulum Stress
term:
id: GO:0034976
label: response to endoplasmic reticulum stress
downstream:
- target: ATF6-Mediated Unfolded Protein Response
causal_link_type: DIRECT
description: >-
ER accumulation of collagens preferentially activates the ATF6 arm
of the UPR in chondrocytes.
evidence:
- reference: PMID:30685387
reference_title: "Suppressing UPR-dependent overactivation of FGFR3 signaling ameliorates SLC26A2-deficient chondrodysplasias."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
As a consequence, the ATF6 arm of the unfolded protein response (UPR) is
preferentially triggered to overactivate FGFR3 signaling by inducing
excessive FGFR3 in slc26a2-/- chondrocytes.
explanation: >-
Collagen retention triggers ATF6-mediated UPR as the preferential
ER stress pathway in SLC26A2-deficient chondrocytes.
evidence:
- reference: PMID:30685387
reference_title: "Suppressing UPR-dependent overactivation of FGFR3 signaling ameliorates SLC26A2-deficient chondrodysplasias."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
Unexpectedly, slc26a2-/- chondrocytes are defective for collagen
secretion, exhibiting intracellular retention and compromised
extracellular deposition of ColII and ColIX.
explanation: >-
Demonstrates that collagen retention is a consequence of SLC26A2
loss, distinct from the proteoglycan undersulfation mechanism.
- name: ATF6-Mediated Unfolded Protein Response
description: >
The ATF6 branch of the unfolded protein response is preferentially
activated in SLC26A2-deficient chondrocytes. ATF6 activation drives
transcriptional upregulation of FGFR3, linking ER stress to growth
factor signaling dysregulation.
cell_types:
- preferred_term: Chondrocyte
term:
id: CL:0000138
label: chondrocyte
biological_processes:
- preferred_term: Endoplasmic Reticulum Unfolded Protein Response
term:
id: GO:0030968
label: endoplasmic reticulum unfolded protein response
downstream:
- target: FGFR3 Overactivation in Chondrocytes
causal_link_type: DIRECT
description: >-
ATF6 induces excessive FGFR3 expression, leading to overactivation
of FGFR3 signaling in chondrocytes.
evidence:
- reference: PMID:30685387
reference_title: "Suppressing UPR-dependent overactivation of FGFR3 signaling ameliorates SLC26A2-deficient chondrodysplasias."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
As a consequence, the ATF6 arm of the unfolded protein response (UPR) is
preferentially triggered to overactivate FGFR3 signaling by inducing
excessive FGFR3 in slc26a2-/- chondrocytes.
explanation: >-
ATF6 directly upregulates FGFR3 expression, establishing the
UPR-to-FGFR3 causal link.
evidence:
- reference: PMID:30685387
reference_title: "Suppressing UPR-dependent overactivation of FGFR3 signaling ameliorates SLC26A2-deficient chondrodysplasias."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
As a consequence, the ATF6 arm of the unfolded protein response (UPR) is
preferentially triggered to overactivate FGFR3 signaling by inducing
excessive FGFR3 in slc26a2-/- chondrocytes.
explanation: >-
Identifies preferential ATF6 activation as the UPR branch responsible
for downstream FGFR3 dysregulation in SLC26A2-deficient chondrocytes.
- name: FGFR3 Overactivation in Chondrocytes
description: >
Excessive FGFR3 signaling, driven by ATF6-mediated transcriptional
upregulation, inhibits chondrocyte proliferation and disrupts the
balance between proliferation and apoptosis in growth plate cartilage.
This represents a major pathogenic mechanism distinct from the primary
matrix defect and a potential therapeutic target.
cell_types:
- preferred_term: Chondrocyte
term:
id: CL:0000138
label: chondrocyte
biological_processes:
- preferred_term: Fibroblast Growth Factor Receptor Signaling Pathway
term:
id: GO:0008543
label: fibroblast growth factor receptor signaling pathway
modifier: INCREASED
evidence:
- reference: PMID:30685387
reference_title: "Suppressing UPR-dependent overactivation of FGFR3 signaling ameliorates SLC26A2-deficient chondrodysplasias."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
Consistently, suppressing FGFR3 signaling by blocking either FGFR3 or
phosphorylation of the downstream effector favors the recovery of
slc26a2-/- cartilage cultures from impaired growth and unbalanced cell
proliferation and apoptosis.
explanation: >-
Blocking FGFR3 rescues growth and proliferation-apoptosis balance,
confirming that FGFR3 overactivation is a key pathogenic driver.
- reference: PMID:38282752
reference_title: "Targeting FGFR3 signaling and drug repurposing for the treatment of SLC26A2-related chondrodysplasia in mouse model."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
Genetic ablation of Fgfr3 in embryonic Slc26a2-deficient chondrocytes
slightly attenuated chondrodysplasia.
explanation: >-
Genetic evidence from Fgfr3/Slc26a2 double knockout confirming that
FGFR3 overactivation contributes to the chondrodysplasia phenotype.
animal_models:
- species: Mus musculus
genotype: Slc26a2 homozygous A386V knock-in (dtd mouse)
description: >
Knock-in mouse carrying the equivalent of the human Finnish founder
mutation. Recapitulates the DTD phenotype with reduced toluidine blue
staining, irregular chondrocytes, delayed secondary ossification, thin
disorganized collagen fibrils, and osteoporosis of long bones. Viable
and used for longitudinal studies of growth and treatment interventions.
evidence:
- reference: PMID:15703192
reference_title: "A diastrophic dysplasia sulfate transporter (SLC26A2) mutant mouse: morphological and biochemical characterization of the resulting chondrodysplasia phenotype."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
The skeletal phenotype included reduced toluidine blue staining of
cartilage, chondrocytes of irregular size, delay in the formation of the
secondary ossification center and osteoporosis of long bones.
explanation: >-
Original characterization of the dtd mouse, demonstrating faithful
modeling of the human DTD cartilage and bone phenotype.
- reference: PMID:23369989
reference_title: "Alteration of proteoglycan sulfation affects bone growth and remodeling."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
Hence, proteoglycans are undersulfated in the cartilage and bone of DTD
patients.
explanation: >-
Detailed in vivo biochemical characterization of the dtd mouse
confirming proteoglycan undersulfation.
- species: Mus musculus
genotype: Slc26a2-/- (global knockout)
description: >
Complete loss-of-function mouse phenocopying the lethal forms of
SLC26A2-related chondrodysplasias (ACG1B and AO2). Used to study the
UPR-FGFR3 pathway and to test FGFR inhibitors and prenatal NAC treatment.
Cartilage-specific deletion (Col2a1-Cre; Slc26a2fl/fl) confirmed
skeleton-specific lethality.
evidence:
- reference: PMID:30685387
reference_title: "Suppressing UPR-dependent overactivation of FGFR3 signaling ameliorates SLC26A2-deficient chondrodysplasias."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
Two lethal forms of human SLC26A2-related chondrodysplasias,
achondrogenesis type IB (ACG1B) and atelosteogenesis type II (AO2), are
phenocopied by slc26a2-/- mice.
explanation: >-
Demonstrates that complete SLC26A2 loss recapitulates the severe end of
the allelic spectrum and confirms skeleton-specific pathology.
genetic:
- name: SLC26A2 Pathogenic Variants
gene_term:
preferred_term: SLC26A2
term:
id: hgnc:10994
label: SLC26A2
association: Causative
notes: >
Biallelic pathogenic variants in SLC26A2 are causative for diastrophic
dysplasia. SLC26A2 encodes a sulfate/chloride antiporter expressed in
chondrocytes and other tissues. Disease severity correlates with residual
sulfate transporter activity: the Finnish founder mutation c.-26+2T>C is
classified as severe, p.Arg279Trp as mild. Homozygosity for the Finnish
mutation typically produces DTD, while compound heterozygosity with milder
alleles can produce rMED.
evidence:
- reference: PMID:24598000
reference_title: "SLC26A2 disease spectrum in Sweden - high frequency of recessive multiple epiphyseal dysplasia (rMED)."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Diastrophic dysplasia (DTD) is an autosomal recessive skeletal dysplasia
caused by SLC26A2 mutations.
explanation: >-
Clinical cohort explicitly states that SLC26A2 mutations cause DTD.
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
From the subjects with available genetic data, 75% (9/12) were
homozygous for the Finnish founder mutation c.-26+2T>C.
explanation: >-
Documents the predominance of the Finnish founder mutation and
genotype-phenotype correlations within the SLC26A2 spectrum.
phenotypes:
- category: Skeletal
name: Disproportionate Short-Limbed Short Stature
frequency: OBLIGATE
description: >
Marked short-limbed short stature is present from birth and growth failure
is progressive through childhood.
phenotype_term:
preferred_term: Disproportionate short-limb short stature
term:
id: HP:0008873
label: Disproportionate short-limb short stature
phenotype_contexts:
- onset:
onset_category: CONGENITAL
notes: Significant growth deficit was usually already present at birth.
evidence:
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The children had usually a significant growth deficit already at birth.
explanation: >-
The Finnish pediatric cohort documents congenital onset of growth
deficiency in DTD.
evidence:
- reference: PMID:9108864
reference_title: "Growth in diastrophic dysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The median adult height was 135.7 cm for the male and 129.0 cm for the
female subjects. The growth failure was progressive partly because of
absent or weak pubertal growth spurt.
explanation: >-
Largest growth study in DTD (121 Finnish patients) with disease-specific
growth curves.
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
In our cohort, all children with DTD phenotype had a short stature.
explanation: >-
The contemporary Finnish cohort confirms that short stature is an
obligate phenotype in clinically typical DTD.
- category: Skeletal
name: Clubfoot
frequency: FREQUENT
description: >
Congenital talipes equinovarus is common and often bilateral.
phenotype_term:
preferred_term: Clubfoot
term:
id: HP:0001762
label: Talipes equinovarus
evidence:
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Seven subjects had bilateral club foot deformity, one had unilateral
club foot and two had metatarsus adductus deformity.
explanation: >-
High prevalence of clubfoot documented in the Finnish pediatric cohort.
- reference: PMID:3065771
reference_title: "Diastrophic dysplasia: a specific prenatal diagnosis by ultrasound."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
club feet, ulnar diviation of hands, shortened phalanges, and, in
particular, abduction of thumbs ('hitchhiker thumbs') and big toes.
explanation: >-
Prenatal ultrasound shows that clubfoot can already be present before
birth in DTD.
- category: Skeletal
name: Hitchhiker Thumb
frequency: FREQUENT
description: >
Abduction of the thumb is a characteristic hand finding that can be
recognized prenatally.
phenotype_term:
preferred_term: Hitchhiker thumb
term:
id: HP:0001234
label: Hitchhiker thumb
evidence:
- reference: PMID:3065771
reference_title: "Diastrophic dysplasia: a specific prenatal diagnosis by ultrasound."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
and, in particular, abduction of thumbs ('hitchhiker thumbs') and big
toes.
explanation: >-
Hitchhiker thumbs explicitly reported in a prenatally diagnosed DTD case.
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Hand abnormalities were present in all subjects; the most common
findings were symphalangism of the fingers (n = 7), hitchhiker’s
thumb/abduction of the thumb (n = 7), flexion tendency of the fingers
(n = 6) and lack of proximal interphalangeal joints (n = 1).
explanation: >-
Hitchhiker thumb was one of the commonest hand abnormalities in the
Finnish pediatric cohort.
- category: Skeletal
name: Finger Symphalangism
frequency: FREQUENT
description: >
Finger symphalangism is a common component of the characteristic hand
phenotype in DTD.
phenotype_term:
preferred_term: Finger symphalangism
term:
id: HP:0009700
label: Finger symphalangism
evidence:
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Hand abnormalities were present in all subjects; the most common
findings were symphalangism of the fingers (n = 7), hitchhiker’s
thumb/abduction of the thumb (n = 7), flexion tendency of the fingers
(n = 6) and lack of proximal interphalangeal joints (n = 1).
explanation: >-
Symphalangism was reported in half of the Finnish pediatric cohort and is
a specific, recurrent hand manifestation of DTD.
- category: Skeletal
name: Joint Contractures
frequency: VERY_FREQUENT
description: >
Progressive contractures of large joints, especially knees, elbows, and
hips. Hip flexion contractures become evident in infancy in over 90% of
patients and are progressive.
phenotype_term:
preferred_term: Joint contracture
term:
id: HP:0034392
label: Joint contracture
evidence:
- reference: PMID:24598000
reference_title: "SLC26A2 disease spectrum in Sweden - high frequency of recessive multiple epiphyseal dysplasia (rMED)."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Clinical features include short stature, joint contractures, spinal
deformities, and cleft palate.
explanation: >-
Joint contractures listed as core clinical feature in the Swedish
SLC26A2 cohort.
- reference: PMID:9546468
reference_title: "Development of the hip in diastrophic dysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Flexion contracture of the hip became evident later in 93% and was
progressive.
explanation: >-
Hip flexion contractures documented in 93% of 50 DTD patients, with
progressive course.
- category: Skeletal
name: Genu Valgum
frequency: VERY_FREQUENT
description: >
Valgus knee deformity is a prominent lower-limb manifestation in DTD.
phenotype_term:
preferred_term: Genu valgum
term:
id: HP:0002857
label: Genu valgum
evidence:
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The prevalence of knee problems was high; valgus deformity (86%), lateral
position of patella (79%) and absence/laxity of the anterior cruciate
ligament (ACL) (71%) were the main features.
explanation: >-
The Finnish pediatric cohort documents genu valgum in 86% of affected
children.
- reference: PMID:14630837
reference_title: "Total knee arthroplasty in patients with diastrophic dysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The knee joint often has an abnormal valgus position and is unstable, and
degeneration of all joint compartments occurs, even during growth.
explanation: >-
Adult surgical series independently confirms valgus knee deformity as a
typical DTD knee phenotype.
- category: Skeletal
name: Patellar Dislocation
frequency: FREQUENT
description: >
Patellar instability and luxation are common components of the DTD knee
phenotype.
phenotype_term:
preferred_term: Patellar dislocation
term:
id: HP:0002999
label: Patellar dislocation
evidence:
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Patellar luxation was seen in over half of the cohort.
explanation: >-
The Finnish pediatric cohort shows that patellar luxation is a common
manifestation in childhood DTD.
- reference: PMID:14630837
reference_title: "Total knee arthroplasty in patients with diastrophic dysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Preoperatively, ten knees had chronic dislocation of the patella.
explanation: >-
Adult surgical series confirms clinically significant patellar
dislocation in advanced DTD knee disease.
- category: Skeletal
name: Cervical Kyphosis
frequency: FREQUENT
description: >
Cervical kyphosis is usually apparent at birth or in early infancy. It
often resolves during growth, but severe cases may require surgery or cause
neurologic compromise.
phenotype_term:
preferred_term: Cervical kyphosis
term:
id: HP:0002947
label: Cervical kyphosis
phenotype_contexts:
- onset:
onset_category: CONGENITAL
notes: Usually shown at the time of birth or on the first cervical images.
evidence:
- reference: PMID:10528373
reference_title: "Cervical kyphosis in diastrophic dysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Cervical kyphosis in diastrophic dysplasia usually is shown at the
time of birth.
explanation: >-
Longitudinal cervical spine study establishes congenital onset for this
phenotype in most affected patients.
evidence:
- reference: PMID:10528373
reference_title: "Cervical kyphosis in diastrophic dysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
In the 24 patients, the kyphosis resolved spontaneously at an average age
of 7.1 years.
explanation: >-
Natural-history study shows that cervical kyphosis commonly improves
spontaneously during childhood.
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
cervical kyphosis was present in 11 subjects (79%).
explanation: >-
Cervical kyphosis in 79% of the Finnish pediatric cohort, with variable
severity and spontaneous resolution in some.
- category: Skeletal
name: Scoliosis
frequency: FREQUENT
description: >
Scoliosis affects a substantial subset of patients and may appear in
infancy or later childhood.
phenotype_term:
preferred_term: Scoliosis
term:
id: HP:0002650
label: Scoliosis
evidence:
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Five children (36%) had scoliosis. The children obtained their diagnosis
of scoliosis at 0-14 years of age. One child had a rapidly progressing
scoliosis at age 1 year.
explanation: >-
The Finnish pediatric cohort documents both the frequency of scoliosis and
the wide variation in age at onset and severity.
- category: Skeletal
name: Lumbar Hyperlordosis
frequency: FREQUENT
description: >
Pronounced lumbar lordosis is a common spinal deformity in DTD.
phenotype_term:
preferred_term: Lumbar hyperlordosis
term:
id: HP:0002938
label: Lumbar hyperlordosis
evidence:
- reference: PMID:10528373
reference_title: "Cervical kyphosis in diastrophic dysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
spinal deformities such as cervical kyphosis, scoliosis, and exaggerated
lumbar lordosis.
explanation: >-
Exaggerated lumbar lordosis listed among typical DTD spinal findings.
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Pronounced lumbar lordosis was present in eight subjects (57%)
explanation: >-
Lumbar lordosis prevalence of 57% in the Finnish pediatric DTD cohort.
- category: Craniofacial
name: Cleft Palate
frequency: FREQUENT
description: >
Cleft palate is a common craniofacial manifestation of DTD.
phenotype_term:
preferred_term: Cleft palate
term:
id: HP:0000175
label: Cleft palate
evidence:
- reference: PMID:24598000
reference_title: "SLC26A2 disease spectrum in Sweden - high frequency of recessive multiple epiphyseal dysplasia (rMED)."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Clinical features include short stature, joint contractures, spinal
deformities, and cleft palate.
explanation: >-
Cleft palate directly listed among DTD features in the clinical cohort.
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Cleft palate was present in 64%.
explanation: >-
High prevalence (64%) of cleft palate in the Finnish pediatric cohort.
- category: Craniofacial
name: Short Chin
frequency: FREQUENT
description: >
A small or short chin is common in DTD; prenatal reports may describe this
craniofacial finding as micrognathia.
phenotype_term:
preferred_term: Short chin
term:
id: HP:0000331
label: Short chin
evidence:
- reference: PMID:3065771
reference_title: "Diastrophic dysplasia: a specific prenatal diagnosis by ultrasound."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
micrognathia, cervical kyphosis, persistent extension limitation in elbow
and knee joints, club feet
explanation: >-
Prenatal ultrasound supports mandibular/chin hypoplasia as part of the
DTD craniofacial phenotype.
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
ten had small chin
explanation: >-
Small chin was present in 10 of 14 children in the Finnish pediatric
cohort.
- category: Ear
name: Cystic Lesions of the Pinnae
frequency: FREQUENT
description: >
Auricular swelling is a characteristic cartilage manifestation in DTD. It
commonly appears in early infancy and may heal with permanent deformity.
phenotype_term:
preferred_term: Cystic lesions of the pinnae
term:
id: HP:0010723
label: Cystic lesions of the pinnae
phenotype_contexts:
- onset:
onset_category: INFANTILE
notes: Auricular swelling commonly occurs in early infancy.
evidence:
- reference: PMID:21414669
reference_title: "Prevention of auricular deformity in children with diastrophic dysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
In diastrophic dysplasia, auricular swelling commonly occurs in early
infancy, inevitably leading to deformity.
explanation: >-
Phenotype-specific otolaryngology case report establishes early infancy
as the typical onset window.
evidence:
- reference: PMID:21414669
reference_title: "Prevention of auricular deformity in children with diastrophic dysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
In diastrophic dysplasia, auricular swelling commonly occurs in early
infancy, inevitably leading to deformity.
explanation: >-
Auricular swelling with later deformity is a recognized DTD-specific ear
manifestation.
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
five had auricular abnormalities (swelling/deformities).
explanation: >-
Auricular swelling and deformities documented in the Finnish cohort.
- category: Respiratory
name: Respiratory Insufficiency
frequency: FREQUENT
description: >
Respiratory insufficiency can complicate the neonatal period in DTD and may
require intensive care.
phenotype_term:
preferred_term: Respiratory insufficiency
term:
id: HP:0002093
label: Respiratory insufficiency
phenotype_contexts:
- onset:
onset_category: NEONATAL
notes: Respiratory insufficiency was reported after birth in the Finnish cohort.
evidence:
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Five subjects (36%) had respiratory insufficiency after birth; three of
them were treated at the intensive care unit and one had severe
pulmonary hypertension.
explanation: >-
The Finnish pediatric cohort directly documents neonatal respiratory
insufficiency in DTD.
evidence:
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Five subjects (36%) had respiratory insufficiency after birth; three of
them were treated at the intensive care unit and one had severe pulmonary
hypertension.
explanation: >-
Respiratory insufficiency after birth occurred in over one third of the
Finnish pediatric cohort.
- category: Skeletal
name: Premature Osteoarthritis
description: >
Degenerative joint disease affects weight-bearing joints early, especially
the hips and knees.
notes: >-
In the Finnish pediatric cohort, arthrosis was already documented at ages 10
and 17 years, and adult hip and knee series show progression to secondary
osteoarthritis and arthroplasty.
phenotype_term:
preferred_term: Premature osteoarthritis
term:
id: HP:0003088
label: Premature osteoarthritis
evidence:
- reference: PMID:14630837
reference_title: "Total knee arthroplasty in patients with diastrophic dysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Diastrophic dysplasia results in severe disproportionate short stature,
generalized joint deformities, and early osteoarthritis.
explanation: >-
Clinical series confirming early osteoarthritis as a defining feature
leading to joint replacement surgery.
- reference: PMID:9546468
reference_title: "Development of the hip in diastrophic dysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The changes in the hip led to secondary osteoarthritis before early
middle age.
explanation: >-
Progressive hip deformity leading to secondary osteoarthritis
documented radiographically.
- category: Skeletal
name: Brachydactyly
description: >
Shortened digits are part of the characteristic hand phenotype in DTD and
can be recognized prenatally.
phenotype_term:
preferred_term: Brachydactyly
term:
id: HP:0001156
label: Brachydactyly
evidence:
- reference: PMID:3065771
reference_title: "Diastrophic dysplasia: a specific prenatal diagnosis by ultrasound."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
shortened phalanges
explanation: >-
Prenatal ultrasound documented shortened phalanges in fetal DTD.
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Radiological findings in DTD include shortened long bones with
metaphyseal flaring, flat epiphyses, kyphoscoliosis, cervical kyphosis,
bowed radius and tibia, proximally situated "hitchhiker" thumb with
shortness of the first metacarpal, brachydactyly and ulnar deviation of
fingers.
explanation: >-
Review of radiographic findings identifies brachydactyly as part of the
canonical DTD hand phenotype.
biochemical:
- name: Reduced Proteoglycan Sulfation
presence: Decreased
notes: >
Cartilage proteoglycans in DTD have glycosaminoglycan chains that are
poorly sulfated but of normal length. Undersulfation of urinary GAGs
has been proposed as a non-invasive biomarker, with some relationship
to clinical severity and underlying SLC26A2 variants.
evidence:
- reference: PMID:8702490
reference_title: "Undersulfation of proteoglycans synthesized by chondrocytes from a patient with achondrogenesis type 1B homozygous for an L483P substitution in the diastrophic dysplasia sulfate transporter."
supports: SUPPORT
evidence_source: IN_VITRO
snippet: >-
The results indicate that the defect of sulfate transport is expressed
in both chondrocytes and fibroblasts and results in the synthesis of
proteoglycans bearing glycosaminoglycan chains which are poorly sulfated
but of normal length.
explanation: >-
First biochemical characterization of proteoglycan undersulfation in
SLC26A2-deficient chondrocytes.
- reference: PMID:37454964
reference_title: "Identification of potential non-invasive biomarkers in diastrophic dysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Undersulfation of urinary GAGs was observed in DTD patients with some
relationship to the clinical severity and underlying SLC26A2 variants.
explanation: >-
Urinary GAG undersulfation validated as a potential non-invasive
biomarker for monitoring DTD.
treatments:
- name: Physiotherapy
description: >
Physical therapy is a mainstay of DTD management, aimed at preserving
joint mobility, preventing contracture progression, and maintaining
ambulation.
treatment_term:
preferred_term: physical therapy
term:
id: MAXO:0000011
label: physical therapy
evidence:
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
There is currently no curative treatment for DTD. The affected
individuals are mainly treated with physiotherapy and corrective
orthopedic surgery.
explanation: >-
Clinical review identifies physiotherapy as standard of care in DTD.
- name: Corrective Orthopedic Surgery
description: >
Orthopedic surgeries are frequently required for clubfoot correction,
spinal stabilization, knee realignment, and total joint arthroplasty
for end-stage osteoarthritis.
treatment_term:
preferred_term: orthopedic surgery
term:
id: MAXO:0000004
label: surgical procedure
evidence:
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
There is currently no curative treatment for DTD. The affected
individuals are mainly treated with physiotherapy and corrective
orthopedic surgery.
explanation: >-
Corrective orthopedic surgery identified as standard clinical
management.
- reference: PMID:14630837
reference_title: "Total knee arthroplasty in patients with diastrophic dysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Total knee arthroplasty substantially improved the function of patients
with diastrophic dysplasia.
explanation: >-
Largest knee replacement series in DTD documenting functional
improvement despite frequent complications.
- name: Genetic Counseling
description: >
Genetic counseling is recommended for families given the 25% recurrence
risk and the availability of prenatal molecular diagnosis.
treatment_term:
preferred_term: genetic counseling
term:
id: MAXO:0000079
label: genetic counseling
evidence:
- reference: PMID:34064542
reference_title: "SLC26A2-Associated Diastrophic Dysplasia and rMED-Clinical Features in Affected Finnish Children and Review of the Literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Genetic testing together with genetic counselling are important parts
of the patient care.
explanation: >-
Finnish clinical review emphasizes the role of genetic testing and
counseling in DTD management.
- name: N-Acetylcysteine (Investigational)
description: >
N-acetyl-L-cysteine (NAC) provides an intracellular source of sulfate
via thiol catabolism, partially compensating for impaired transmembrane
sulfate uptake. In the dtd mouse model, prenatal NAC administration
increased cartilage proteoglycan sulfation and partially rescued
skeletal morphology.
treatment_term:
preferred_term: pharmacotherapy (N-acetylcysteine)
term:
id: MAXO:0000058
label: pharmacotherapy
evidence:
- reference: PMID:26206888
reference_title: "N-acetylcysteine treatment ameliorates the skeletal phenotype of a mouse model of diastrophic dysplasia."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
a marked increase in PG sulfation was observed in newborns from
NAC-treated pregnancies when compared with the placebo group.
explanation: >-
Prenatal NAC treatment of dtd mice increased proteoglycan sulfation
and partially rescued bone morphology.
- reference: PMID:16719839
reference_title: "In vivo contribution of amino acid sulfur to cartilage proteoglycan sulfation."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
The relative amount of sulfated disaccharides increased in mutant mice
treated with NAC compared with the placebo group, indicating an increase
in proteoglycan sulfation due to NAC catabolism
explanation: >-
Early proof-of-concept showing that exogenous NAC can increase cartilage
proteoglycan sulfation in the dtd mouse model.
- name: FGFR3 Signaling Inhibition (Investigational)
description: >
Experimental FGFR inhibition (e.g., NVP-BGJ398) has rescued impaired
cartilage growth in SLC26A2-deficient mouse models by counteracting
UPR-dependent FGFR3 overactivation. Both in vitro cartilage culture and
in utero maternal administration showed therapeutic effects.
treatment_term:
preferred_term: FGFR inhibitor therapy
term:
id: MAXO:0000058
label: pharmacotherapy
target_mechanisms:
- target: FGFR3 Overactivation in Chondrocytes
treatment_effect: INHIBITS
evidence:
- reference: PMID:30685387
reference_title: "Suppressing UPR-dependent overactivation of FGFR3 signaling ameliorates SLC26A2-deficient chondrodysplasias."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
Consistently, suppressing FGFR3 signaling by blocking either FGFR3 or
phosphorylation of the downstream effector favors the recovery of
slc26a2-/- cartilage cultures from impaired growth and unbalanced cell
proliferation and apoptosis.
explanation: >-
FGFR3 inhibition rescues growth plate defects in slc26a2-/- cartilage
cultures.
evidence:
- reference: PMID:30685387
reference_title: "Suppressing UPR-dependent overactivation of FGFR3 signaling ameliorates SLC26A2-deficient chondrodysplasias."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
Moreover, administration of an FGFR inhibitor to pregnant females shows
therapeutic effects on pathological features in slc26a2-/- newborns.
explanation: >-
In utero FGFR inhibitor treatment improved skeletal features in
SLC26A2-knockout newborn mice.
- reference: PMID:38282752
reference_title: "Targeting FGFR3 signaling and drug repurposing for the treatment of SLC26A2-related chondrodysplasia in mouse model."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
in vivo experiments showed significant alleviation of impaired
chondrocyte differentiation, and micro-CT analysis showed a clear
improvement in trabecular bone microarchitectural parameters.
explanation: >-
Postnatal NVP-BGJ398 treatment in an inducible Slc26a2-cKO mouse
improved trabecular bone architecture, extending the therapeutic
evidence from prenatal to postnatal intervention.
datasets: []
Question: You are an expert researcher providing comprehensive, well-cited information.
Provide detailed information focusing on: 1. Key concepts and definitions with current understanding 2. Recent developments and latest research (prioritize 2023-2024 sources) 3. Current applications and real-world implementations 4. Expert opinions and analysis from authoritative sources 5. Relevant statistics and data from recent studies
Format as a comprehensive research report with proper citations. Include URLs and publication dates where available. Always prioritize recent, authoritative sources and provide specific citations for all major claims.
Please provide a comprehensive research report on the pathophysiology of Diastrophic Dysplasia. Focus on the molecular and cellular mechanisms underlying disease progression.
Structure your response as a narrative that could be used to populate a disease knowledge base entry with: - Pathophysiology description - Gene/protein annotations with ontology terms (HGNC, GO) - Phenotype associations (HP terms) - Cell type involvement (CL terms) - Anatomical locations (UBERON terms) - Chemical entities (CHEBI terms) - Evidence items with PMIDs
Diastrophic dysplasia (DTD) is a rare autosomal recessive chondrodysplasia affecting cartilage and bone development, classically assigned MIM/OMIM #222600 and caused by biallelic pathogenic variants in SLC26A2 (also known as DTDST; OMIM #606718). (paganini2023identificationofpotential pages 1-3, silveira2022slc26a2dtdstspectruma pages 1-2)
MONDO mapping (available from Open Targets evidence in this run): MONDO_0009107 (diastrophic dysplasia). (gramegnatota2023chondrodysplasiascausedby pages 42-46)
SLC26A2 encodes a transmembrane sulfate/chloride antiporter that is critical for inorganic sulfate uptake into chondrocytes; intracellular sulfate is required to generate activated sulfate donors (e.g., PAPS) that drive glycosaminoglycan (GAG)/proteoglycan sulfation. Reduced sulfate transport results in undersulfated cartilage proteoglycans, which disrupt cartilage extracellular matrix (ECM) structure and endochondral ossification, producing the skeletal phenotype. (paganini2023identificationofpotential pages 1-3, gramegnatota2023chondrodysplasiascausedbya pages 42-46)
A key disease principle is the residual-activity model: across SLC26A2-related conditions (including lethal and non-lethal phenotypes), clinical severity correlates with residual sulfate transport capacity and degree of proteoglycan undersulfation. (paganini2023identificationofpotential pages 1-3)
DTD pathophysiology begins with impaired sulfate uptake via SLC26A2, lowering the sulfate available for proteoglycan/GAG sulfation in cartilage. This results in cartilage proteoglycan undersulfation detectable biochemically and histochemically in mouse models and consistent with patient observations. (forlino2005adiastrophicdysplasia pages 8-9, paganini2023identificationofpotential pages 1-3)
Quantitative example (mouse dtd A386V model): chondroitin sulfation at birth was reported as approximately ~0.7 sulfate/disaccharide in dtd vs ~0.9 in wild type, with strong regional variation across cartilage zones. (mertz2012matrixdisruptionsgrowth pages 1-1)
Undersulfated proteoglycans alter cartilage ECM composition, architecture, and mechanics (reduced water retention and collagen “unmasking”), providing a mechanistic bridge from a transport defect to tissue fragility and abnormal morphogenesis. (gramegnatota2023chondrodysplasiascausedbya pages 42-46)
In the dtd mouse, reduced chondroitin sulfation correlated with reduced collagen orientation, including in the protective collagen layer of articular cartilage; this was proposed to contribute to progressive cartilage degeneration despite partial normalization of sulfation with age. (mertz2012matrixdisruptionsgrowth pages 1-1, mertz2012matrixdisruptionsgrowth media e64dc09b)
Mouse models show developmental consequences consistent with impaired endochondral ossification: - progressive changes in proteoglycan sulfation with age (P1–P60) (forlino2005adiastrophicdysplasia pages 8-9) - delayed secondary ossification center formation (forlino2005adiastrophicdysplasia pages 1-2) - growth-plate disorganization at later time points (P60) (forlino2005adiastrophicdysplasia pages 8-9)
Mechanistically, reduced proliferation has been linked to altered Indian hedgehog (Ihh) signaling and cell-cycle control via reduced p130 phosphorylation affecting E2F transcription factors, causing a G1 block (reported in a synthesis of model data). (gramegnatota2023chondrodysplasiascausedbyc pages 127-129)
Beyond undersulfation, severe Slc26a2 deficiency models demonstrate a second major mechanism: impaired secretion of major cartilage collagens.
In slc26a2−/− chondrocytes, ColII and ColIX show strong intracellular retention with reduced extracellular deposition; ultrastructural data include ER distension and intracellular matrix-containing vesicles. (zheng2019suppressinguprdependentoveractivation pages 6-8)
This intracellular retention triggers ER stress and the unfolded protein response (UPR), with preferential activation/nuclear localization of ATF6, and increased ATF6 and FGFR3 protein levels. (zheng2019suppressinguprdependentoveractivation pages 6-8)
The same work links ATF6 to FGFR3 transcriptional upregulation and demonstrates overactivation of FGFR3 signaling (increased p-ERK1/2 and p-STAT1; hypersensitivity to FGF2). (zheng2019suppressinguprdependentoveractivation pages 6-8)
Interpretation (expert mechanistic synthesis): DTD pathophysiology is not solely “undersulfation,” but can include a UPR-driven signaling pathology (ATF6→FGFR3) that is targetable pharmacologically in preclinical models; this provides a mechanistic rationale for pathway-directed therapy. (zheng2019suppressinguprdependentoveractivation pages 1-2, li2024targetingfgfr3signaling pages 11-13)
From the mechanistic evidence in this corpus, disrupted processes include: - Sulfate transmembrane transport (SLC26A2-dependent). (paganini2023identificationofpotential pages 1-3, forlino2005adiastrophicdysplasia pages 8-9) - Proteoglycan/GAG sulfation and cartilage matrix assembly. (paganini2023identificationofpotential pages 1-3, gramegnatota2023chondrodysplasiascausedbya pages 42-46) - Extracellular matrix organization (collagen orientation/architecture and proteoglycan-dependent hydration). (mertz2012matrixdisruptionsgrowth pages 1-1, gramegnatota2023chondrodysplasiascausedbya pages 42-46) - Endochondral ossification / growth plate development (delayed ossification, reduced proliferation/differentiation). (forlino2005adiastrophicdysplasia pages 1-2, gramegnatota2023chondrodysplasiascausedbyc pages 127-129) - ER stress / unfolded protein response (ATF6 arm) and downstream FGFR3 signaling (in severe deficiency). (zheng2019suppressinguprdependentoveractivation pages 6-8)
(Exact GO identifiers were not retrievable from the provided text excerpts; mapping would require ontology lookup beyond the retrieved text.)
A major, widely cited principle is that phenotype severity correlates with residual transport activity, but the same genotype can produce variable phenotypes. (paganini2023identificationofpotential pages 1-3, silveira2022slc26a2dtdstspectruma pages 9-10)
Population and allele effects: - Finland shows a strong founder effect for c.-26+2T>C, commonly homozygous in DTD, and the incidence has decreased over decades with increased prenatal diagnostics. (harkonen2021slc26a2associateddiastrophicdysplasia pages 1-2, harkonen2021slc26a2associateddiastrophicdysplasia pages 5-7) - p.R279W is frequent outside Finland and is associated with mild phenotype in homozygosity and can mitigate severity in compound heterozygosity (“rescue”). (silveira2022slc26a2dtdstspectruma pages 7-8) - Adult DTD example variants include p.Val341del and p.Cys653Ser in compound heterozygosity. (bondarenko2023slc26a2relateddiastrophic pages 1-2)
A 2023 Bone study evaluated two non-invasive biomarkers for DTD: - Urinary GAG sulfation profiling via chondroitin sulfate disaccharide HPLC after chondroitinase digestion, reporting undersulfation in DTD patients. (paganini2023identificationofpotential pages 1-3) - CXM (N-terminal collagen X fragment) in dried blood spots, a “real-time marker of endochondral ossification and growth velocity,” reported lower-than-normal in most patients, with interpretation limited by strong age/sex/growth-velocity dependence. (paganini2023identificationofpotential pages 1-3)
These assays are positioned as practical tools to support future natural-history studies and clinical trials in DTD. (paganini2023identificationofpotential pages 1-3)
Preclinical work in 2024 further operationalizes the UPR→FGFR3 model and evaluates FGFR inhibition: - Genetic reduction of Fgfr3 reduced pathway activity (p-ERK1/2 and p-STAT1 down) and partially alleviated phenotypes. (li2024targetingfgfr3signaling pages 11-13) - Pharmacologic inhibition using NVP-BGJ398 increased body size in Slc26a2 cKO mice at 49 days with prolonged treatment. (li2024targetingfgfr3signaling pages 11-13)
Authors explicitly caution that dosing for oncologic indications is much higher than dosing considered for pediatric skeletal indications, emphasizing translational constraints. (li2024targetingfgfr3signaling pages 11-13)
A 2024 Disease Models & Mechanisms paper extends SLC26A2 biology beyond cartilage into odontogenesis, reporting: - significant reduction of sulfated GAG in upper molar tooth germs (P<0.0001) (yoshida2024slc26a2mediatedsulfatemetabolism pages 8-11) - KEGG enrichment identifying Wnt signaling as the most significantly enriched among downregulated genes (yoshida2024slc26a2mediatedsulfatemetabolism pages 8-11)
This supports a broader framework in which sulfate transport can modulate developmental signaling programs in multiple tissues. (yoshida2024slc26a2mediatedsulfatemetabolism pages 8-11)
In 2024, human primary chondrocyte experiments in SLC26A2-related MED-4 showed mutant SLC26A2 mislocalization and altered differentiation markers (e.g., decreased COL10A1/RUNX2/MMP13, increased ACAN), supporting a direct influence of SLC26A2 variants on chondrocyte differentiation programs. (li2024biallelicvariantsin pages 1-2)
There is no established disease-modifying therapy; management is largely supportive, including physiotherapy and corrective orthopedic surgery. (harkonen2021slc26a2associateddiastrophicdysplasia pages 1-2)
In the Finnish cohort, common surgeries included knee operations (n=9), cleft palate repair (n=8), club foot surgeries (n=7), and Achilles tenotomy (n=6). (harkonen2021slc26a2associateddiastrophicdysplasia pages 4-5)
Urinary GAG sulfation and dried-blood-spot CXM are proposed as practical non-invasive biomarkers for DTD monitoring and future trials. (paganini2023identificationofpotential pages 1-3)
The following artifact organizes entities, mechanisms, biomarkers, and phenotypes for direct knowledge-base ingestion.
| Entity type | Identifier/ontology mapping | Role in pathophysiology | Key evidence | URL/DOI | Citation context ID(s) |
|---|---|---|---|---|---|
| Gene/Protein | SLC26A2 (HGNC symbol); MONDO: MONDO_0009107; OMIM disease 222600; gene OMIM 606718 | Plasma-membrane sulfate/chloride antiporter that supplies intracellular sulfate for proteoglycan sulfation; biallelic loss causes DTD spectrum. | Paganini et al., 2023: SLC26A2 “encodes for a transmembrane sulfate transporter”; severity correlates with “residual sulfate transport.” Silveira et al., 2022 identifies DTD OMIM #222600 and SLC26A2/DTDST OMIM #606718. | https://doi.org/10.1016/j.bone.2023.116838 ; https://doi.org/10.1159/000525020 | (paganini2023identificationofpotential pages 1-3, silveira2022slc26a2dtdstspectruma pages 1-2) |
| Pathway | GO ID not retrieved; sulfate transport / proteoglycan sulfation / PAPS-dependent sulfation | Reduced sulfate uptake lowers intracellular sulfate availability for sulfation, causing undersulfated cartilage proteoglycans. | Gramegna-Tota, 2023: impaired SLC26A2 function “producing reduced intracellular sulfate and undersulfation of proteoglycans (PGs).” Forlino et al., 2005: “Chondroitin sulfate proteoglycans were undersulfated.” | https://doi.org/10.1093/hmg/ddi079 | (gramegnatota2023chondrodysplasiascausedbya pages 42-46, forlino2005adiastrophicdysplasia pages 8-9) |
| Pathway | GO ID not retrieved; endochondral ossification | Undersulfated matrix disrupts growth-plate cartilage and endochondral bone formation. | Paganini et al., 2023: PG sulfation is essential for “normal cartilaginous matrix structure and endochondral ossification.” | https://doi.org/10.1016/j.bone.2023.116838 | (paganini2023identificationofpotential pages 1-3) |
| Pathway | GO ID not retrieved; FGFR3 signaling | In severe Slc26a2 deficiency, ATF6-dependent UPR increases FGFR3 signaling, suppressing cartilage growth and differentiation. | Zheng et al., 2019: ATF6 induces excessive FGFR3 expression; p-ERK1/2 and p-STAT1 are increased. Li et al., 2024: NVP-BGJ398 caused a “significant increase in body size” in Slc26a2 cKO mice. | https://doi.org/10.1016/j.ebiom.2019.01.010 ; https://doi.org/10.1016/j.jot.2023.09.003 | (zheng2019suppressinguprdependentoveractivation pages 6-8, li2024targetingfgfr3signaling pages 11-13) |
| Pathway | GO ID not retrieved; UPR / ATF6 ER-stress pathway | Collagen retention in chondrocytes triggers ER stress, with preferential ATF6 activation in severe disease models. | Zheng et al., 2019: “increased expression of ATF4, BIP, CHOP, ATF6 and XBP1” with preferential ATF6 nuclear localization. | https://doi.org/10.1016/j.ebiom.2019.01.010 | (zheng2019suppressinguprdependentoveractivation pages 6-8, zheng2019suppressinguprdependentoveractivation pages 1-2) |
| Pathway | GO ID not retrieved; Indian hedgehog (Ihh) signaling | Altered Ihh signaling contributes to reduced chondrocyte proliferation and growth-plate dysfunction in hypomorphic DTD models. | Gramegna-Tota, 2023: reduced proliferation is associated with “altered Indian hedgehog (Ihh) signaling.” | URL not retrieved | (gramegnatota2023chondrodysplasiascausedbyc pages 127-129) |
| Pathway | GO ID not retrieved; cell-cycle regulation (p130/E2F) | Reduced p130 phosphorylation causes G1 block and contributes to impaired proliferation of growth-plate chondrocytes. | Gramegna-Tota, 2023: reduced p130 phosphorylation affects E2F transcription factors and causes a “G1 phase block.” | URL not retrieved | (gramegnatota2023chondrodysplasiascausedbyc pages 127-129) |
| Pathway | GO ID not retrieved; Wnt signaling | Recent non-cartilage work suggests Slc26a2-dependent sulfate metabolism can modulate Wnt-linked differentiation programs. | Yoshida et al., 2024: KEGG analysis found Wnt signaling was the “most significantly enriched pathway among downregulated genes”; sulfated GAG reduction in upper molars was P<0.0001. | https://doi.org/10.1242/dmm.052107 | (yoshida2024slc26a2mediatedsulfatemetabolism pages 8-11) |
| Cell type | CL: chondrocyte ID not retrieved | Primary disease cell type; defective sulfate uptake alters proliferation, differentiation, matrix secretion, and survival responses. | Forlino et al., 2005: sulfate uptake impaired in chondrocytes; Zheng et al., 2019: intracellular retention of ColII/ColIX in slc26a2−/− chondrocytes. | https://doi.org/10.1093/hmg/ddi079 ; https://doi.org/10.1016/j.ebiom.2019.01.010 | (forlino2005adiastrophicdysplasia pages 1-2, zheng2019suppressinguprdependentoveractivation pages 6-8) |
| Cell type | CL ID not retrieved; hypertrophic chondrocyte | Terminal differentiation is delayed/perturbed, contributing to abnormal ossification and growth-plate maturation. | Forlino et al., 2005: few apoptotic hypertrophic chondrocytes at P21; Li et al., 2024 reports altered Col X and differentiation markers after FGFR3 targeting. | https://doi.org/10.1093/hmg/ddi079 ; https://doi.org/10.1016/j.jot.2023.09.003 | (forlino2005adiastrophicdysplasia pages 8-9, li2024targetingfgfr3signaling pages 11-13) |
| Cell type | CL ID not retrieved; osteoblast | Sulfate uptake is affected in osteoblasts, but major proteoglycan undersulfation is most evident in cartilage; bone remodeling changes are likely secondary to matrix defects. | Forlino et al., 2005: uptake impaired in osteoblasts; Gualeni et al., 2013: high osteoclast resorption/reduced osteoblast activity despite normal cell numbers. | https://doi.org/10.1093/hmg/ddi079 ; https://doi.org/10.1016/j.bone.2013.01.036 | (forlino2005adiastrophicdysplasia pages 1-2, gualeni2013alterationofproteoglycan pages 9-9) |
| Cell type | CL ID not retrieved; fibroblast | Useful diagnostic/functional cell type for demonstrating reduced sulfate uptake, though cartilage is most pathologically affected. | Paganini 2020 summary: “reduced sulfate uptake in fibroblasts”; Forlino et al., 2005 also notes impaired uptake in fibroblasts. | https://doi.org/10.3390/ijms21082710 ; https://doi.org/10.1093/hmg/ddi079 | (paganini2020skeletaldysplasiascaused pages 9-10, forlino2005adiastrophicdysplasia pages 1-2) |
| Tissue/Anatomy | UBERON ID not retrieved; cartilage | Principal affected tissue because cartilage ECM is rich in sulfated proteoglycans and highly dependent on sulfate flux. | Gramegna-Tota, 2023: significant PG undersulfation was detected “only in cartilage.” | URL not retrieved | (gramegnatota2023chondrodysplasiascausedbyc pages 127-129) |
| Tissue/Anatomy | UBERON ID not retrieved; growth plate cartilage | Regional undersulfation disrupts proliferation and matrix architecture in zones crucial for bone elongation. | Mertz et al., 2012: undersulfation was mild overall but strong in “narrow articular and growth plate regions crucial for bone development.” | https://doi.org/10.1074/jbc.m110.116467 | (mertz2012matrixdisruptionsgrowth pages 1-1, mertz2012matrixdisruptionsgrowth media e64dc09b) |
| Tissue/Anatomy | UBERON ID not retrieved; articular cartilage | Matrix abnormalities and collagen disorganization in the articular surface likely drive progressive degeneration with age. | Mertz et al., 2012: collagen orientation was reduced in the protective surface layer; articular cartilage “degrades with age.” | https://doi.org/10.1074/jbc.m110.116467 | (mertz2012matrixdisruptionsgrowth pages 1-1, mertz2012matrixdisruptionsgrowth media e64dc09b) |
| Tissue/Anatomy | UBERON ID not retrieved; bone / secondary ossification center | Delayed ossification and altered bone remodeling emerge downstream of abnormal cartilage matrix and growth-plate biology. | Forlino et al., 2005: “delayed secondary ossification center formation”; Gualeni et al., 2013: alteration of PG sulfation affects bone growth and remodeling. | https://doi.org/10.1093/hmg/ddi079 ; https://doi.org/10.1016/j.bone.2013.01.036 | (forlino2005adiastrophicdysplasia pages 1-2, gualeni2013alterationofproteoglycan pages 9-9) |
| Cellular component | GO ID not retrieved; plasma membrane | SLC26A2 acts at the cell membrane to import sulfate into target cells. | Paganini et al., 2023 and Paganini 2020 describe SLC26A2 as a “transmembrane sulfate transporter” / “Sulfate/chloride antiporter present on cell membrane.” | https://doi.org/10.1016/j.bone.2023.116838 ; https://doi.org/10.3390/ijms21082710 | (paganini2023identificationofpotential pages 1-3, paganini2020skeletaldysplasiascaused pages 9-10) |
| Cellular component | GO ID not retrieved; endoplasmic reticulum | Severe deficiency causes intracellular collagen retention, ER distension, and ER-stress signaling. | Zheng et al., 2019: “massive intracellular accumulation of matrix-containing vesicles, ER distension in chondrocytes.” | https://doi.org/10.1016/j.ebiom.2019.01.010 | (zheng2019suppressinguprdependentoveractivation pages 6-8) |
| Cellular component | GO ID not retrieved; extracellular matrix | Undersulfated PGs alter matrix composition, hydration, collagen organization, and tissue mechanics. | Gramegna-Tota, 2023: undersulfated PGs alter ECM “composition, architecture, signalling and mechanics”; Mertz et al., 2012 links undersulfation to collagen disorientation. | https://doi.org/10.1074/jbc.m110.116467 | (gramegnatota2023chondrodysplasiascausedbya pages 42-46, mertz2012matrixdisruptionsgrowth pages 1-1) |
| Chemical entity | CHEBI ID not retrieved; sulfate / inorganic sulfate | Limiting substrate whose defective uptake is the initiating biochemical lesion. | Gramegna-Tota, 2023 notes intracellular sulfate pool depends on extracellular uptake; Forlino et al., 2005: “sulfate uptake is impaired in dtd animals.” | https://doi.org/10.1093/hmg/ddi079 | (gramegnatota2023chondrodysplasiascausedbya pages 42-46, forlino2005adiastrophicdysplasia pages 8-9) |
| Chemical entity | CHEBI ID not retrieved; PAPS | Universal activated sulfate donor whose supply becomes limiting when intracellular sulfate is reduced. | Gramegna-Tota, 2023: insufficient intracellular sulfate “limits formation of PAPS, the universal sulfate donor.” | URL not retrieved | (gramegnatota2023chondrodysplasiascausedbya pages 42-46) |
| Chemical entity | CHEBI ID not retrieved; chondroitin sulfate / sulfated GAGs | Major matrix component whose undersulfation tracks with structural and biomechanical defects in cartilage. | Mertz et al., 2012: chondroitin sulfation about ~0.7 sulfate/disaccharide in dtd vs ~0.9 in wild type; region-specific deficits mapped across cartilage. | https://doi.org/10.1074/jbc.m110.116467 | (mertz2012matrixdisruptionsgrowth pages 1-1, mertz2012matrixdisruptionsgrowth media e64dc09b) |
| Chemical entity | CHEBI ID not retrieved; N-acetylcysteine (NAC) | Experimental sulfate surrogate/thiol donor proposed to improve intracellular sulfate availability and proteoglycan sulfation. | Härkönen et al., 2021: “Dtd mice treated with NAC showed an increase in cartilage proteoglycan sulfation and improvement of the skeletal phenotype.” Li et al., 2024: NAC selected “as an alternative to intracellular sulfate.” | https://doi.org/10.3390/genes12050714 ; https://doi.org/10.1016/j.jot.2023.09.003 | (harkonen2021slc26a2associateddiastrophicdysplasia pages 1-2, li2024targetingfgfr3signaling pages 11-13) |
| Chemical entity | CHEBI ID not retrieved; NVP-BGJ398 / infigratinib | Experimental FGFR inhibitor repurposed to suppress pathogenic FGFR3 overactivation in Slc26a2-deficient models. | Li et al., 2024: prolonged treatment led to a “significant increase in body size in Slc26a2 cKO mice at 49 days postnatally.” | https://doi.org/10.1016/j.jot.2023.09.003 | (li2024targetingfgfr3signaling pages 11-13) |
| Biomarker | ID not retrieved; urinary GAG sulfation / chondroitin sulfate disaccharides | Non-invasive readout of systemic proteoglycan undersulfation. | Paganini et al., 2023: “Undersulfation of urinary GAGs” measured by HPLC after chondroitinase digestion; both biomarkers judged “promising assays.” | https://doi.org/10.1016/j.bone.2023.116838 | (paganini2023identificationofpotential pages 1-3) |
| Biomarker | ID not retrieved; CXM (N-terminal collagen X fragment) | Candidate blood-spot biomarker of endochondral ossification and growth velocity in DTD. | Paganini et al., 2023: CXM is “a real-time marker of endochondral ossification and growth velocity”; most patients had “Lower than normal CXM levels.” | https://doi.org/10.1016/j.bone.2023.116838 | (paganini2023identificationofpotential pages 1-3) |
| Phenotype/Clinical | HP ID not retrieved; short-limb short stature / disproportionate short stature | Reflects chronically reduced endochondral growth from growth-plate dysfunction. | Härkönen et al., 2021: median height SDS at last follow-up was −5.5 for girls and −4.1 for boys with DTD. | https://doi.org/10.3390/genes12050714 | (harkonen2021slc26a2associateddiastrophicdysplasia pages 4-5) |
| Phenotype/Clinical | HP ID not retrieved; joint dysplasia / contractures | Matrix and growth-plate abnormalities alter joint shape and mobility from early development onward. | Bondarenko et al., 2023 describes “defective joint and skeletal development”; Härkönen et al., 2021 reports frequent knee/patellar problems and multiple knee surgeries. | https://doi.org/10.2478/bjmg-2022-0018 ; https://doi.org/10.3390/genes12050714 | (bondarenko2023slc26a2relateddiastrophic pages 1-2, harkonen2021slc26a2associateddiastrophicdysplasia pages 4-5) |
| Phenotype/Clinical | HP ID not retrieved; spinal deformity (scoliosis/kyphosis) | Progressive vertebral and connective-tissue involvement follows abnormal cartilage/bone development. | Bondarenko et al., 2023 notes “progressive spinal deformity (scoliosis/kyphosis).” | https://doi.org/10.2478/bjmg-2022-0018 | (bondarenko2023slc26a2relateddiastrophic pages 1-2) |
| Phenotype/Clinical | HP ID not retrieved; ear swelling / malformed pinnae | Classic external ear phenotype in DTD, likely reflecting abnormal cartilage development outside the appendicular skeleton. | Bondarenko et al., 2023 mentions external ear/pinna abnormalities; DTD is historically characterized by cystic swelling of the external ear. | https://doi.org/10.2478/bjmg-2022-0018 | (bondarenko2023slc26a2relateddiastrophic pages 1-2) |
| Phenotype/Clinical | HP ID not retrieved; cleft palate | Craniofacial/cartilage developmental consequence common in clinical cohorts. | Härkönen et al., 2021: cleft palate in 64% of cohort; cleft palate repair performed in n=8. | https://doi.org/10.3390/genes12050714 | (harkonen2021slc26a2associateddiastrophicdysplasia pages 4-5) |
| Phenotype/Clinical | HP ID not retrieved; respiratory insufficiency in neonates | Severe thoracic/airway consequences can complicate neonatal course in DTD. | Härkönen et al., 2021: respiratory insufficiency after birth in 36% (5/14), with three requiring intensive care. | https://doi.org/10.3390/genes12050714 | (harkonen2021slc26a2associateddiastrophicdysplasia pages 4-5) |
| Phenotype/Clinical | HP ID not retrieved; prenatal short limbs / skeletal abnormality on ultrasound | Real-world prenatal screening often detects DTD before birth. | Härkönen et al., 2021: 77% (10/13) suspected prenatally; structural ultrasound showed short limbs in all 10 suspected pregnancies. | https://doi.org/10.3390/genes12050714 | (harkonen2021slc26a2associateddiastrophicdysplasia pages 4-5) |
| Phenotype/Clinical | HP ID not retrieved; genotype–phenotype continuum | Residual transporter activity modifies severity across ACG1B/AO2, DTD, and rMED. | Paganini et al., 2023: severity ranges from lethal forms to rMED and “correlates with the level of residual sulfate transport.” Silveira et al., 2022: R279W is mild in homozygosity and can rescue more severe alleles. | https://doi.org/10.1016/j.bone.2023.116838 ; https://doi.org/10.1159/000525020 | (paganini2023identificationofpotential pages 1-3, silveira2022slc26a2dtdstspectruma pages 7-8, silveira2022slc26a2dtdstspectruma pages 9-10) |
Table: This table organizes key entities, mechanisms, biomarkers, and clinical phenotypes relevant to diastrophic dysplasia for a disease knowledge base. It links each item to ontology/identifier information where available, concise mechanistic roles, and directly cited supporting evidence.
The user requested PMIDs for mechanistic claims; however, the retrieved full-text excerpts in this run largely provide DOIs and URLs but not PMIDs. Mechanistic claims above are therefore cited to the retrieved document context IDs (as required by the toolchain) and can be cross-walked to PMIDs using the DOIs/metadata if needed. (paganini2023identificationofpotential pages 1-3, li2024targetingfgfr3signaling pages 11-13)
References
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(silveira2022slc26a2dtdstspectruma pages 1-2): Cynthia Silveira, Karina da Costa Silveira, Maria D. Lacarrubba-Flores, Maurício T. Sakata, Silvia N. Carbognani, Juan Llerena Jr., Carolina A. Moreno, and Denise P. Cavalcanti. Slc26a2/dtdst spectrum: a cohort of 12 patients associated with a comprehensive review of the genotype-phenotype correlation. Molecular Syndromology, 13:485-495, Jun 2022. URL: https://doi.org/10.1159/000525020, doi:10.1159/000525020. This article has 10 citations and is from a peer-reviewed journal.
(gramegnatota2023chondrodysplasiascausedby pages 42-46): C GRAMEGNA-TOTA. Chondrodysplasias caused by defects in glycosaminoglycan biosynthesis: deep phenotyping and therapeutic approaches using in vitro and in vivo model. Unknown journal, 2023.
(gramegnatota2023chondrodysplasiascausedbya pages 42-46): C GRAMEGNA-TOTA. Chondrodysplasias caused by defects in glycosaminoglycan biosynthesis: deep phenotyping and therapeutic approaches using in vitro and in vivo model. Unknown journal, 2023.
(forlino2005adiastrophicdysplasia pages 8-9): A. Forlino, R. Piazza, C. Tiveron, S. Della Torre, L. Tatangelo, L. Bonafė, Benedetta Gualeni, A. Romano, Fabio Pecora, A. Superti-Furga, G. Cetta, and A. Rossi. A diastrophic dysplasia sulfate transporter (slc26a2) mutant mouse: morphological and biochemical characterization of the resulting chondrodysplasia phenotype. Human molecular genetics, 14 6:859-71, Mar 2005. URL: https://doi.org/10.1093/hmg/ddi079, doi:10.1093/hmg/ddi079. This article has 166 citations and is from a domain leading peer-reviewed journal.
(mertz2012matrixdisruptionsgrowth pages 1-1): Edward L. Mertz, Marcella Facchini, Anna T. Pham, Benedetta Gualeni, Fabio De Leonardis, Antonio Rossi, and Antonella Forlino. Matrix disruptions, growth, and degradation of cartilage with impaired sulfation. Journal of Biological Chemistry, 287:22030-22042, Jun 2012. URL: https://doi.org/10.1074/jbc.m110.116467, doi:10.1074/jbc.m110.116467. This article has 30 citations and is from a domain leading peer-reviewed journal.
(mertz2012matrixdisruptionsgrowth media e64dc09b): Edward L. Mertz, Marcella Facchini, Anna T. Pham, Benedetta Gualeni, Fabio De Leonardis, Antonio Rossi, and Antonella Forlino. Matrix disruptions, growth, and degradation of cartilage with impaired sulfation. Journal of Biological Chemistry, 287:22030-22042, Jun 2012. URL: https://doi.org/10.1074/jbc.m110.116467, doi:10.1074/jbc.m110.116467. This article has 30 citations and is from a domain leading peer-reviewed journal.
(forlino2005adiastrophicdysplasia pages 1-2): A. Forlino, R. Piazza, C. Tiveron, S. Della Torre, L. Tatangelo, L. Bonafė, Benedetta Gualeni, A. Romano, Fabio Pecora, A. Superti-Furga, G. Cetta, and A. Rossi. A diastrophic dysplasia sulfate transporter (slc26a2) mutant mouse: morphological and biochemical characterization of the resulting chondrodysplasia phenotype. Human molecular genetics, 14 6:859-71, Mar 2005. URL: https://doi.org/10.1093/hmg/ddi079, doi:10.1093/hmg/ddi079. This article has 166 citations and is from a domain leading peer-reviewed journal.
(gramegnatota2023chondrodysplasiascausedbyc pages 127-129): C GRAMEGNA-TOTA. Chondrodysplasias caused by defects in glycosaminoglycan biosynthesis: deep phenotyping and therapeutic approaches using in vitro and in vivo model. Unknown journal, 2023.
(zheng2019suppressinguprdependentoveractivation pages 6-8): Chao Zheng, Xisheng Lin, Xiaolong Xu, Cheng Wang, Jinru Zhou, Bo Gao, Jingzhou Fan, Weiguang Lu, Yaqian Hu, Qiang Jie, Zhuojing Luo, and Liu Yang. Suppressing upr-dependent overactivation of fgfr3 signaling ameliorates slc26a2-deficient chondrodysplasias. EBioMedicine, 40:695-709, Feb 2019. URL: https://doi.org/10.1016/j.ebiom.2019.01.010, doi:10.1016/j.ebiom.2019.01.010. This article has 44 citations and is from a peer-reviewed journal.
(zheng2019suppressinguprdependentoveractivation pages 1-2): Chao Zheng, Xisheng Lin, Xiaolong Xu, Cheng Wang, Jinru Zhou, Bo Gao, Jingzhou Fan, Weiguang Lu, Yaqian Hu, Qiang Jie, Zhuojing Luo, and Liu Yang. Suppressing upr-dependent overactivation of fgfr3 signaling ameliorates slc26a2-deficient chondrodysplasias. EBioMedicine, 40:695-709, Feb 2019. URL: https://doi.org/10.1016/j.ebiom.2019.01.010, doi:10.1016/j.ebiom.2019.01.010. This article has 44 citations and is from a peer-reviewed journal.
(li2024targetingfgfr3signaling pages 11-13): Pan Li, Dong Wang, Weiguang Lu, Xin He, Jingyan Hu, Haitao Yun, Chengxiang Zhao, Liu Yang, Qiang Jie, and Zhuojing Luo. Targeting fgfr3 signaling and drug repurposing for the treatment of slc26a2-related chondrodysplasia in mouse model. Journal of Orthopaedic Translation, 44:88-101, Jan 2024. URL: https://doi.org/10.1016/j.jot.2023.09.003, doi:10.1016/j.jot.2023.09.003. This article has 4 citations.
(harkonen2021slc26a2associateddiastrophicdysplasia pages 1-2): Helmi Härkönen, Petra Loid, and Outi Mäkitie. Slc26a2-associated diastrophic dysplasia and rmed—clinical features in affected finnish children and review of the literature. Genes, 12:714, May 2021. URL: https://doi.org/10.3390/genes12050714, doi:10.3390/genes12050714. This article has 34 citations.
(paganini2020skeletaldysplasiascaused pages 9-10): Chiara Paganini, Chiara Gramegna Tota, Andrea Superti-Furga, and Antonio Rossi. Skeletal dysplasias caused by sulfation defects. International Journal of Molecular Sciences, 21:2710, Apr 2020. URL: https://doi.org/10.3390/ijms21082710, doi:10.3390/ijms21082710. This article has 38 citations.
(bondarenko2023slc26a2relateddiastrophic pages 1-2): M. Bondarenko, I. Haiboniuk, I. Solovei, Y. Shargorodska, and H. Makukh. Slc26a2 related diastrophic dysplasia in 42-years ukrainian women. Balkan Journal of Medical Genetics : BJMG, 25:83-90, Dec 2023. URL: https://doi.org/10.2478/bjmg-2022-0018, doi:10.2478/bjmg-2022-0018. This article has 3 citations.
(harkonen2021slc26a2associateddiastrophicdysplasia pages 4-5): Helmi Härkönen, Petra Loid, and Outi Mäkitie. Slc26a2-associated diastrophic dysplasia and rmed—clinical features in affected finnish children and review of the literature. Genes, 12:714, May 2021. URL: https://doi.org/10.3390/genes12050714, doi:10.3390/genes12050714. This article has 34 citations.
(silveira2022slc26a2dtdstspectruma pages 9-10): Cynthia Silveira, Karina da Costa Silveira, Maria D. Lacarrubba-Flores, Maurício T. Sakata, Silvia N. Carbognani, Juan Llerena Jr., Carolina A. Moreno, and Denise P. Cavalcanti. Slc26a2/dtdst spectrum: a cohort of 12 patients associated with a comprehensive review of the genotype-phenotype correlation. Molecular Syndromology, 13:485-495, Jun 2022. URL: https://doi.org/10.1159/000525020, doi:10.1159/000525020. This article has 10 citations and is from a peer-reviewed journal.
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Diastrophic dysplasia is caused by loss-of-function mutations in the SLC26A2 gene, which encodes a sulfate transporter essential for cartilage development (pmc.ncbi.nlm.nih.gov). SLC26A2 is a transmembrane sulfate/chloride antiporter that imports inorganic sulfate (SO₄²⁻) into chondrocytes, providing the sulfate needed to synthesize sulfated glycosaminoglycans (GAGs) and proteoglycans in the cartilage matrix (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). As a result of SLC26A2 deficiency, chondrocytes have an intracellular sulfate depletion, leading to undersulfation of cartilage proteoglycans (pmc.ncbi.nlm.nih.gov) (www.ncbi.nlm.nih.gov). Undersulfated proteoglycans cannot form a proper extracellular matrix, which impairs endochondral bone formation in the growth plates (www.ncbi.nlm.nih.gov). In essence, the lack of sulfate disrupts the normal assembly of cartilage matrix, weakening its structure and function. This mechanism explains the short stature and skeletal malformations seen in DTD, as proteoglycan undersulfation affects cartilage extracellular matrix composition and prevents proper ossification of developing bones (www.ncbi.nlm.nih.gov). Notably, the severity of disease correlates with residual SLC26A2 activity: mutations that allow some residual sulfate transport produce milder phenotypes, whereas near-complete loss of function causes the most severe, often lethal, forms (www.ncbi.nlm.nih.gov).
Recent mechanistic insights: Beyond the classic “proteoglycan undersulfation” theory, new research has uncovered additional cellular pathways in DTD. In a 2019 study, Zheng et al. showed that SLC26A2 deficiency triggers an unfolded protein response (UPR) in chondrocytes due to improper processing of cartilage collagens (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Specifically, loss of SLC26A2 leads to defective secretion of type II collagen and other matrix proteins, causing them to accumulate in the endoplasmic reticulum and activate the ATF6-mediated UPR pathway (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). This chronic ER stress not only leads to some chondrocyte cell death but also alters signaling pathways crucial for growth plate function. Notably, UPR activation was found to upregulate fibroblast growth factor receptor 3 (FGFR3) in chondrocytes, leading to overactivation of FGFR3 signaling (pmc.ncbi.nlm.nih.gov). FGFR3 is a key negative regulator of chondrocyte proliferation and differentiation, and its overactivation strongly inhibits cartilage growth. Zheng et al. demonstrated that in SLC26A2-deficient mice, ATF6-driven UPR signaling causes aberrant FGFR3 overactivity that “dominates the pathogenesis” of the skeletal defects (pmc.ncbi.nlm.nih.gov). Importantly, blocking FGFR3 signaling (using FGFR3 inhibitors or blocking downstream ERK phosphorylation) was shown to rescue impaired cartilage growth in vitro and to ameliorate skeletal abnormalities in SLC26A2–knockout mouse models (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). This finding highlights FGFR3 overactivation as a novel contributor to DTD pathophysiology and a potential therapeutic target (pmc.ncbi.nlm.nih.gov). In addition, earlier studies indicated that proteoglycan undersulfation may disrupt the distribution of Indian hedgehog (IHH) in the growth plate, leading to altered IHH/PTHrP signaling and reduced chondrocyte proliferation (www.ncbi.nlm.nih.gov). Thus, multiple dysregulated pathways — from matrix biochemistry (sulfation) to ER stress (UPR) to signal transduction (FGFR3, IHH) — collectively underlie the pathogenesis of diastrophic dysplasia.
Several biological processes are perturbed in diastrophic dysplasia, corresponding to gene ontology (GO) terms:
Overall, DTD disrupts the fundamental processes of cartilage matrix production and skeletal development, as well as stress-response pathways in chondrocytes. These perturbations at the molecular level manifest as the impaired biological processes listed above, driving the disease phenotype. Each of these processes can be mapped to GO annotations that facilitate understanding the multi-level impact of the SLC26A2 mutation on cellular function.
Pathogenic mechanisms in DTD involve specific cellular compartments and structures:
In summary, the pathology of DTD spans multiple cellular compartments: the defect begins at the plasma membrane (sulfate transport), disrupts biochemical processes in the Golgi, causes stress in the ER, and results in an abnormal extracellular matrix in cartilage tissue. Each of these cellular components plays a role in the cascade from gene mutation to tissue-level disease.
Prenatal Development: The disease process starts in utero. With biallelic SLC26A2 mutations, the initial trigger is the absence or dysfunction of the sulfate transporter from the earliest stages of cartilage formation. During fetal skeletal development, chondrocytes cannot import enough sulfate, leading to undersulfated proteoglycans as cartilage models of bones are laid down (pmc.ncbi.nlm.nih.gov). Consequently, the fetal cartilage matrix is aberrant – it is less hydrated and structurally weak. This causes stunted growth of long bones and dysplastic shape of skeletal elements before birth (rarediseases.org). Clinically, many characteristics of DTD are already present at birth (e.g. shortened limbs, clubfoot, hitchhiker thumbs), indicating that the pathological sequence has been operating throughout embryonic bone development. In severe cases (depending on the mutation severity), the disease can even be perinatally lethal due to extreme skeletal underdevelopment or respiratory failure from a small thoracic cage (www.ncbi.nlm.nih.gov). Most commonly, however, affected infants survive, and their neonatal period is marked by recognizable orthopedic abnormalities (often including the hallmark cystic ear swelling present in ~67% of newborns) (www.ncbi.nlm.nih.gov).
Childhood Growth Phase: As the child grows, the pathophysiological processes continue into infancy and childhood. The growth plates remain abnormal – chondrocyte proliferation is suboptimal and endochondral ossification is slow, so the limbs grow disproportionately slowly. This leads to progressive limb length discrepancy compared to peers, and short stature (dwarfism) becomes increasingly evident (rarediseases.org). Joint contractures may worsen as the child attempts to use joints that have malformed cartilage and bone alignment; without early intervention (such as physical therapy and casting), fixed deformities of knees, elbows, and other joints can develop or progress (www.ncbi.nlm.nih.gov). Spinal deformities often become more pronounced with growth: a mild congenital kyphosis may progress to a significant thoracolumbar kyphoscoliosis over childhood due to asymmetric growth of vertebrae and weak ligaments (rarediseases.org). Throughout this phase, the underlying molecular issues persist – chondrocytes remain under stress. Histologic studies in a DTD mouse model show that the cartilage matrix stays abnormally structured with cystic spaces and reduced sulfation (www.ncbi.nlm.nih.gov), indicating the biochemical lesion is ongoing. There are no distinct “remissions” or normal phases in this disorder; rather, the degree of growth impairment accumulates over time. Supportive care (e.g. orthopedic surgeries for clubfoot or cervical spine stabilization if needed) is often undertaken during childhood to manage complications of the progressing skeletal deformities (www.ncbi.nlm.nih.gov).
Adolescence and Adulthood: By adolescence, linear growth has largely ceased, and final height is very short (often around the 10th percentile of normal or below) (www.ncbi.nlm.nih.gov). In adulthood, degenerative changes become a key aspect of disease progression. Due to years of abnormal joint mechanics and undersulfated cartilage, patients typically develop early-onset osteoarthritis in weight-bearing joints and the spine (www.ncbi.nlm.nih.gov). Pain and limited mobility from joint degeneration often appear in early adulthood, which is much earlier than in the general population. For instance, hip and knee osteoarthritis can cause severe pain by the second or third decade, sometimes necessitating joint replacement surgeries in young adults (www.ncbi.nlm.nih.gov). The spine may stiffen or further curve, and in some cases neurological complications can arise if there is spinal cord compression (due to cervical kyphosis or stenosis in the dysplastic vertebrae) (www.ncbi.nlm.nih.gov). The ear cartilage swelling seen in infancy usually resolves, but it may leave a “cauliflower ear” deformity long-term (www.ncbi.nlm.nih.gov). Importantly, the disease does not typically affect lifespan beyond perinatal risks – adults with DTD can live a normal lifespan, but with significant physical limitations. The later stages of DTD are therefore characterized by managing chronic orthopedic issues rather than further “progression” of the molecular defect. In summary, the pathological sequence is set in motion during development (leading to congenital anomalies), and then manifests as growth failure and skeletal deformities progressing through childhood, followed by early degenerative joint disease in adulthood. Each stage reflects the cumulative consequences of the fundamental sulfate transport defect on the skeleton over time.
(No formal “staging” system exists for DTD, but we can view its progression in these developmental phases. Throughout, the underlying molecular pathology – impaired sulfate uptake and matrix sulfation – remains active, driving the observed clinical course.)
Diastrophic dysplasia has a characteristic set of clinical phenotypes (Human Phenotype Ontology terms) that directly result from its molecular and cellular pathology:
Each of these phenotypic manifestations is linked to the underlying molecular pathology of diastrophic dysplasia. In summary, short stature and limb shortening result from defective endochondral ossification at the growth plates (due to matrix undersulfation) (www.ncbi.nlm.nih.gov). Skeletal deformities like hitchhiker thumb, clubfoot, and scoliosis arise from dysplastic development of cartilage models in those regions. Joint problems (contractures and early arthritis) reflect the abnormal composition and early degeneration of articular cartilage. The ear and palate findings highlight that even non-weight-bearing cartilage and craniofacial structures are affected by the fundamental biochemical lesion (sulfate transport defect).
Notably, intelligence and internal organ development are normal in DTD – this emphasizes that the SLC26A2 pathophysiology is highly specific to cartilaginous tissues. All the clinical features can be traced back to how undersulfated proteoglycans and disturbed chondrocyte function alter the structure and biomechanical properties of developing tissues. As one study succinctly stated, “proteoglycans that are not sulfated or are insufficiently sulfated… affect the composition of the extracellular matrix and lead to impairment of proteoglycan deposition, which is necessary for proper endochondral bone formation” (www.ncbi.nlm.nih.gov). This cascade – from molecular defect to tissue dysfunction – underlies the distinctive phenotype of diastrophic dysplasia.
(Note: All evidence statements are supported by the cited sources. Publication dates and PMIDs are provided where available to emphasize recency and authority of sources. Clinical descriptions are drawn from GeneReviews (www.ncbi.nlm.nih.gov) and NORD (rarediseases.org), whereas mechanistic details are supported by primary research articles as cited above.)