Langer Mesomelic Dysplasia

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Classifications

Harrison's Part

ISDS Skeletal Nosology

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Inheritance

1

Pseudoautosomal recessive HP:0034341

SHOX lies in pseudoautosomal region 1, which escapes X inactivation and recombines between X and Y, so SHOX alleles follow autosomal rules in both sexes. LMD requires two defective SHOX alleles. The characteristic pedigree is two LWD parents with a 25% risk per pregnancy of an LMD child; consanguinity and pseudodominant transmission (an affected parent mating with a heterozygous carrier) both occur.

Pseudoautosomal recessive inheritance Penetrance: COMPLETE

Show evidence (2 references)

PMID:20301394 SUPPORT Human Clinical

"If both parents have SHOX deficiency, the offspring have a 50% chance of having a SHOX deficiency disorder, a 25% chance of having Langer type of mesomelic dwarfism, and a 25% chance of having neither condition."

GeneReviews states the recurrence arithmetic that defines the recessive relationship of LMD to heterozygous SHOX deficiency.

PMID:12116253 SUPPORT Human Clinical

"The same mutation was present in the heterozygous state in the proband's father and in the maternal grandmother, both of whom had features of LWD."

Documents the same allele producing LWD when heterozygous and LMD when homozygous within one pedigree — the clearest possible demonstration of the dosage relationship.

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Discussions and Knowledge Gaps

3

Can any rodent model be informative about SHOX loss, given that the mouse genome has no SHOX ortholog at all?

HUMAN MODEL MISMATCH no_mouse_shox_ortholog

Attached to

pathophysiology#Complete Loss of SHOX Transcription Factor Activity

SHOX was lost from the rodent lineage; the mouse carries only the paralog Shox2, which has a different expression domain (proximal rather than middle limb segment). So the standard route for validating a transcription factor's developmental role — a knockout mouse — is unavailable for this disease, and the mechanism curated here rests entirely on human genetics and human growth plate histopathology. This is a structural limitation on the evidence, not a gap that more mouse work would close, and it is why the entry carries no ``animal_models`` section.

Does recombinant growth hormone produce any height gain in complete (biallelic) SHOX deficiency, or does the licensed benefit in heterozygous SHOX deficiency simply not transfer?

KNOWLEDGE GAP gh_efficacy_in_complete_shox_deficiency

Attached to

treatments#Recombinant Growth Hormone Therapy

The evidence base is asymmetric in a way that matters at the bedside: randomized trial data in heterozygous SHOX deficiency versus a single reported LMD case in which GH produced an IGF-1 response and no growth. One negative case cannot settle the question, but it is the only LMD-specific datum there is, and it points the opposite way from the licensed indication. Because LMD numbers fewer than a hundred published cases, a trial is implausible; a pooled registry of treated patients is the realistic route.

How early and how reliably can LMD be distinguished on prenatal ultrasound from the other causes of severe fetal limb shortening?

KNOWLEDGE GAP prenatal_recognition_of_lmd

Attached to

diagnosis#Radiographic and Clinical Recognition

Sonographic suspicion has been reported as early as 12+3 weeks, but the published prenatal experience is dominated by families already known to carry SHOX defects, where the prior probability is high. The operating characteristics of fetal ultrasound for LMD in an unselected population with short fetal long bones are unknown, which is the situation in which the question is actually asked.

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Pathophysiology

5

Complete Loss of SHOX Transcription Factor Activity

SHOX encodes a paired-related homeodomain transcription factor expressed in growth plate chondrocytes. In LMD both alleles are defective, by any of three routes that converge on absent functional protein: deletion of the coding region, homozygous deletion of the PAR1 enhancers that drive SHOX expression in the limb, or homeodomain missense substitutions that impair DNA binding and nuclear import. The homozygous or hemizygous defect reported in the defining series lay in exon 6a, implicating the SHOXa isoform specifically as the one required for normal skeletal development.

SHOX hgnc:10853

Genetic context SHOX hgnc:10853 allele_type: SHOX coding deletion, PAR1 enhancer deletion, or homeodomain missense zygosity: HOMOZYGOUS functional_impact_category: LOSS_OF_FUNCTION

SHOX sequence-specific DNA binding GO:0000981 ⇓ LOSS OF FUNCTION

Downstream

Loss of SHOX Chondrogenic Target Regulation Absent SHOX protein removes the transcriptional program it drives.

Show evidence (3 references)

PMID:12116254 SUPPORT Human Clinical

"SHOX abnormalities were detected in all five probands. One was a homozygote or hemizygote and two were compound heterozygotes."

Establishes biallelic SHOX defects in every proband of the defining series, which is the claim of this node.

PMID:12116254 SUPPORT Human Clinical

"The homozygous or hemizygous mutation was in exon 6a, implying that the SHOXa isoform is essential for normal skeletal development."

Supports the isoform-specific requirement asserted in this node's description.

PMID:12116253 SUPPORT Human Clinical

"This C to T transition is predicted to cause an arginine to cysteine amino acid change in a highly conserved region of the recognition helix of the homeodomain, which may reduce the stability of the interaction between the SHOX protein and its target DNA."

Supplies the molecular consequence of the missense route to complete deficiency: impaired homeodomain-DNA interaction. The source hedges ("predicted", "may"), and this node inherits that hedge.

Loss of SHOX Chondrogenic Target Regulation

SHOX does not act alone on one target. It directly induces NPPB (natriuretic peptide B / BNP), whose co-expression with SHOX in prehypertrophic and hypertrophic chondrocytes places the pair in growth plate regulation; it interacts with SOX5 and SOX6 to regulate aggrecan synthesis and cartilage matrix assembly; and in a chondrogenic context it represses FGFR3, itself a negative regulator of endochondral growth. Losing SHOX therefore removes a growth-promoting input and simultaneously de-represses a growth-inhibiting one — a plausible reason the biallelic phenotype is disproportionately severe rather than simply twice as bad.

Regulation of chondrocyte gene expression by SHOX GO:0006357 ↓ DECREASED

Downstream

Disorganized Growth Plate Chondrocyte Maturation Loss of the SHOX target program is what the disorganized growth plate is downstream of.

Show evidence (2 references)

PMID:42553923 SUPPORT Human Clinical

"The SHOX protein also directly induces transcription of the NPPB gene, encoding the natriuretic peptide BNP, a direct SHOX target whose co-expression with SHOX in prehypertrophic and hypertrophic chondrocytes implicates this axis in growth plate regulation"

Establishes NPPB as a direct SHOX target expressed in the relevant chondrocyte populations.

PMID:42553923 SUPPORT In Vitro

"Given that the FGFR3 protein is a known negative regulator of endochondral bone growth, this SHOX protein-mediated repression is likely critical for growth homeostasis in mesomelic segments."

Supports the FGFR3 de-repression limb of this node. The source itself hedges ("likely"), and the repression was shown in chicken micromass culture rather than human cartilage, so this is recorded as PARTIAL IN_VITRO rather than as an established human mechanism.

Zeugopod-Restricted SHOX Expression Domain

Why the middle limb segment and not the whole limb. In human embryos SHOX and its paralog SHOX2 occupy complementary limb domains: SHOX in the zeugopod (forearm, lower leg), SHOX2 more proximally in the stylopod. The paralog therefore cannot compensate where SHOX is lost, and the deficit is confined to the segment SHOX alone patterns. This is the anatomical explanation of "mesomelic", and it is a positional argument rather than a severity one.

limb development GO:0060173 ↓ DECREASED

Downstream

Disorganized Growth Plate Chondrocyte Maturation This node is a precondition, not a consequence: the expression domain pre-exists the mutation and is what confines the growth-plate disorganization to zeugopodal cartilage. It has no incoming edge for that reason.

Severe Mesomelic Limb Shortening The segment SHOX patterns alone is the segment that fails.

Show evidence (2 references)

PMID:42553923 SUPPORT Human Clinical

"In human embryos, SHOX and SHOX2 display complementary expression profiles during limb development: SHOX is detected in the middle portion of the limb corresponding to the mesomelic segments, whereas SHOX2 is expressed more proximally"

Establishes the complementary expression domains that make the phenotype segment-specific.

PMID:42553923 SUPPORT Model Organism

"conditional Shox2 inactivation in murine limbs, a species that has lost the SHOX gene during evolution, leads to severe stylopodial (humerus, femur) shortening, with relative sparing of the zeugopod, confirming the complementary segmental roles of these paralogs"

The reciprocal experiment: removing the proximal paralog produces the proximal phenotype, corroborating the segmental division of labour.

Disorganized Growth Plate Chondrocyte Maturation

SHOX-deficient growth plates lose their normal parallel columnar arrangement of chondrocytes, with tandem stacking replaced by a side-by-side arrangement, an expanded hypertrophic layer, and evidence of abnormal endochondral ossification. Unusually for a disorder this rare, the lesion has been described in LMD tissue itself and not only inferred from the heterozygous state: fetal growth plates from terminated LMD pregnancies show shortened, side-by-side chondrocyte columns in the proliferative zone and enlarged reserve-zone chondrocytes, with mutant SHOX protein still detectable across all three zones.

Growth plate chondrocyte CL:1000217 Hypertrophic chondrocyte CL:0000743

Growth plate chondrocyte differentiation GO:0003418 ↓ DECREASED Endochondral bone morphogenesis GO:0060350 ↓ DECREASED

Downstream

Severe Mesomelic Limb Shortening Failure of ordered chondrocyte maturation truncates longitudinal growth of the middle limb segment.

Show evidence (3 references)

PMID:11677662 SUPPORT Human Clinical

"A widespread disorganisation of physeal anatomy was revealed with disruption of the normal parallel columnar arrangement of chondrocytes. Tandem stacking of maturing chondrocytes within columns was replaced by a side-by-side arrangement."

Direct human growth-plate histopathology of SHOX deficiency. The material is from heterozygous LWD patients; the LMD-specific fetal histology in the next item shows the same columnar disorganization.

PMID:42553923 SUPPORT Human Clinical

"significant cellular disorganization was evident in the proliferative zone, where chondrocyte columns were shortened and stacked side-by-side rather than in a normal longitudinal orientation. Additionally, enlargement of chondrocytes was observed in the reserve zone."

Histopathology from LMD fetal growth plates specifically, which is what makes this node an observation in the disease rather than a transfer from the heterozygous state.

PMID:25110390 SUPPORT Human Clinical

"histopathological analyses showed a disrupted columnar arrangement of chondrocytes and an expanded hypertrophic layer of the growth plate. Recent studies have suggested that perturbed programmed cell death of hypertrophic chondrocytes may underlie the skeletal changes related to SHOX deficiency."

Review confirming the growth-plate lesion across SHOX deficiency and naming hypertrophic chondrocyte apoptosis as a candidate underlying process.

Severe Mesomelic Limb Shortening

The clinical endpoint: the middle limb segments are the most severely affected, with the ulna and fibula hypoplastic or absent and the radius and tibia short and bowed. Because both alleles are lost, the shortening is substantially more severe than in Leri-Weill dyschondrosteosis and is already detectable prenatally.

Downstream

Severe Mesomelia The zeugopod is where SHOX alone patterns growth, so it is the segment that fails.

Disproportionate Short Stature Stature loss is limb-restricted, which is why the trunk and pelvis remain normally proportioned.

Ulnar Hypoplasia The ulna is the zeugopod bone that fails most severely, often losing its distal epiphysis.

Fibular Hypoplasia The lower-limb counterpart of the ulnar lesion, with the fibular head ossification centre often absent.

Radial Bowing Unequal growth failure between the paired forearm bones bows the radius.

Madelung Deformity Where distal radial growth fails asymmetrically against the ulna, the same wrist geometry as in Leri-Weill dyschondrosteosis results — but the biallelic lesion distorts the whole zeugopod, so the classic deformity is often obscured rather than accentuated.

Genu Valgum Valgus at the knee and ankle follows from the tibia and fibula being shortened by different amounts, not from a primary joint lesion.

Show evidence (1 reference)

PMID:12116254 SUPPORT Human Clinical

"These findings confirm clinical inferences that Langer mesomelic dysplasia is the homozygous form of Leri-Weill dyschondrosteosis and add to our understanding of genotype/phenotype relationships in SHOX deficiency disorders."

Establishes the dosage relationship between the two entities, which is what makes this node's severity claim mechanistic rather than descriptive.

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Pathograph

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

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Phenotypes

9

Ear 1

Conductive Hearing Loss OCCASIONAL Conductive hearing impairment HP:0000405

Show evidence (1 reference)

PMID:42553923 SUPPORT Human Clinical

"Whether this represents a rare phenotypic manifestation of SHOX deficiency or a coincidental finding in a consanguineous family remains unclear"

The source's own statement of the uncertainty, which is why this phenotype is recorded as PARTIAL rather than SUPPORT.

Head and Neck 1

Micrognathia OCCASIONAL HP:0000347

Show evidence (1 reference)

PMID:42553923 SUPPORT Human Clinical

"Although originally considered a defining feature of LMD (Langer, 1967), hypoplastic mandible is now recognized as inconsistently present"

Supports the feature's occurrence while refuting its status as a defining criterion, which is why the frequency here is OCCASIONAL rather than VERY_FREQUENT.

Limbs 4

Ulnar Hypoplasia VERY_FREQUENT Hypoplasia of the ulna HP:0003022

Show evidence (1 reference)

PMID:42553923 SUPPORT Human Clinical

"In the upper limbs, both the radius and ulna exhibit marked deformities; the ulna is typically bowed and hypoplastic, often lacking the distal epiphysis."

Describes the ulnar lesion, including the absent distal epiphysis.

Radial Bowing FREQUENT HP:0002986

Show evidence (1 reference)

PMID:42553923 SUPPORT Human Clinical

"The radius demonstrates varying degrees of bowing and may be associated with Madelung-type deformity, although this feature shows considerable variability: it may be severe, mild, or even absent in individual patients"

Supports both the bowing and the explicit variability of the Madelung component in this disorder.

Genu Valgum FREQUENT HP:0002857

Show evidence (1 reference)

PMID:42553923 SUPPORT Human Clinical

"The disproportion between tibial and fibular lengths contributes to characteristic valgus deformities at the knees (genu valgum) and ankles, which may be the presenting feature leading to orthopedic consultation"

Gives both the mechanism of the valgus deformity and its role as a presenting complaint.

Madelung Deformity OCCASIONAL HP:0003067

Show evidence (1 reference)

PMID:42553923 SUPPORT Human Clinical

"The radius demonstrates varying degrees of bowing and may be associated with Madelung-type deformity, although this feature shows considerable variability: it may be severe, mild, or even absent in individual patients"

Supports the feature's occurrence while explicitly refuting its constancy, which is why the frequency is OCCASIONAL and the evidence PARTIAL.

Growth 1

Disproportionate Short Stature VERY_FREQUENT HP:0003498

Show evidence (2 references)

PMID:42553923 SUPPORT Human Clinical

"Reported cases of LMD involve various degrees of limb skeletal abnormalities, whereas the cranium, chest, spine, and pelvis typically show normal proportions"

Establishes that the growth deficit is limb-restricted, which is the content of "disproportionate" here.

PMID:20301394 SUPPORT Human Clinical

"a 25% chance of having Langer type of mesomelic dwarfism"

GeneReviews names the entity as a mesomelic dwarfism.

Other 2

Severe Mesomelia VERY_FREQUENT HP:0003027

Show evidence (1 reference)

PMID:42553923 SUPPORT Human Clinical

"Radiographic findings demonstrate significant dysplastic and hypoplastic changes in all long bones, with a characteristic and disproportionate mesomelic shortening of the forearms and lower legs. Defective ossification is particularly prominent in the distal ulna and proximal fibula"

States the radiographic distribution of the shortening and where ossification fails most.

Fibular Hypoplasia VERY_FREQUENT HP:0003038

Show evidence (1 reference)

PMID:42553923 SUPPORT Human Clinical

"whereas the fibula is often rudimentary and proximally shortened. The ossification center for the fibular head may be absent"

Describes the fibular lesion and the absent ossification centre.

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Genetic Associations

1

SHOX

Gene: SHOX hgnc:10853 relationship_type: CAUSATIVE

Show evidence (4 references)

PMID:12116254 SUPPORT Human Clinical

"SHOX abnormalities were detected in all five probands. One was a homozygote or hemizygote and two were compound heterozygotes."

Establishes SHOX as causative with biallelic defects in every proband studied.

PMID:23883335 SUPPORT Human Clinical

"a homozygous deletion of the 3' enhancer of the SHOX gene, and consanguineous parents affected by Léri-Weill dyschondrosteosis"

Documents the enhancer-deletion route to LMD with an intact coding region, the allele class most easily missed by coding-only testing.

PMID:41042407 SUPPORT Human Clinical

"A novel SHOX gene splice donor variant (c.486 + 2T > C) was found in homozygous form in individuals with LMD, and in heterozygous form in individuals with ISS."

One allele, two doses, two diagnoses within a single family — the cleanest available demonstration that the LMD/ISS distinction is gene dosage rather than allele identity. It also adds splice-site variants to the allelic spectrum alongside deletions and missense.

+ 1 more reference

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Medical Actions

3

Recombinant Growth Hormone Therapy

Action: Growth hormone therapy Ontology label: Hormone Replacement Therapy NCIT:C15599

Agent: recombinant human growth hormone NCIT:C837

rhGH is licensed and effective for SHOX-deficient short stature, with a reported final-height gain of 7 to 10 cm — but that evidence is entirely from heterozygous patients. In LMD the one documented treated case, an individual with combined LMD and Turner syndrome, showed a biochemical response with rising IGF-1 and no height-velocity response at all, with the height deficit widening over four years. Complete SHOX deficiency plausibly removes the growth plate substrate on which GH acts, so the extrapolation from LWD is not merely unproven but has been contradicted once. Offer it, if at all, with that explicitly on the table.

Mechanism Target:

Disorganized Growth Plate Chondrocyte Maturation — Acts on the growth plate that the SHOX lesion disorganizes, but through a SHOX-independent axis. It does not restore SHOX target regulation, which is why the height gain is partial in a complete-loss genotype.

Show evidence (4 references)

PMID:42553923 REFUTE Human Clinical

"In particular, GH therapy failed to produce growth acceleration in a documented case involving a combination of LMD and Turner syndrome."

The single reported LMD treatment experience is a negative result, which is why this evidence item is REFUTE rather than SUPPORT.

PMID:42553923 REFUTE Human Clinical

"The authors concluded that GH therapy may not be beneficial in the setting of complete SHOX deficiency, although no worsening of the skeletal deformities was observed"

States the conclusion drawn from that case, including the reassurance that treatment did not make the skeletal phenotype worse.

PMID:20301394 SUPPORT Human Clinical

"For prepubertal children with SHOX-deficient short stature, recombinant human growth hormone (rhGH therapy) (dose 50 µg/kg body weight/day) should be offered. The therapeutic effect is a gain in final height of 7 to 10 cm."

The recommendation and effect size that would be extrapolated to LMD. PARTIAL because the population is the heterozygous spectrum, not LMD.

+ 1 more reference

Orthopedic Surgery for Limb Deformity

Action: orthopedic surgical procedure Ontology label: Orthopedic Surgical Procedure NCIT:C16186

Corrective and lengthening procedures for the forearm and lower leg deformity. Operative decisions in LMD are harder than in LWD because the ulna and fibula may be largely absent rather than merely deformed.

Mechanism Target:

Severe Mesomelic Limb Shortening — Addresses the established limb anatomy. Purely anatomical correction; the upstream chondrogenic defect is unmodified.

Show evidence (1 reference)

PMID:20301394 SUPPORT Human Clinical

"Different operative procedures have been attempted to decrease pain and restore wrist function."

GeneReviews describes operative management within SHOX deficiency, though for the LWD Madelung deformity rather than the LMD long-bone deficiency; recorded as PARTIAL for that reason.

Genetic Counseling

Category: Counseling / Informational Action: genetic counseling Ontology label: Genetic Counseling NCIT:C15240

Counseling is unusual here because the parents are themselves usually affected. Two LWD parents carry a 25% recurrence risk per pregnancy for LMD and a 50% risk for LWD, so the counseling conversation is about a spectrum of outcomes rather than affected-versus-unaffected.

Show evidence (1 reference)

PMID:20301394 SUPPORT Human Clinical

"If both parents have SHOX deficiency, the offspring have a 50% chance of having a SHOX deficiency disorder, a 25% chance of having Langer type of mesomelic dwarfism, and a 25% chance of having neither condition."

Supplies the exact recurrence arithmetic this section describes.

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Diagnosis

2

Radiographic and Clinical Recognition

Suspected from severe mesomelic dwarfism with hypoplastic or absent ulna and fibula, short bowed radius and tibia, and mandibular hypoplasia. Because the deformity is already present in the fetus, LMD can be recognized on prenatal ultrasound and confirmed by fetal radiography and autopsy where a pregnancy is not continued. A family history of Leri-Weill dyschondrosteosis in both parents is a strong pointer.

diagnostic radiography NCIT:C17369

Show evidence (1 reference)

PMID:23883335 SUPPORT Human Clinical

"A competent pathologist could provide important diagnostic information, orienting or confirming the echographic or genetic suspect"

Supports the role of fetal pathological and radiographic assessment alongside ultrasound and molecular testing.

Molecular Confirmation of Biallelic SHOX/PAR1 Defect

Diagnosis is confirmed by demonstrating two defective SHOX alleles. Testing must cover the PAR1 enhancer regions as well as the coding sequence, since homozygous enhancer deletions with an intact SHOX coding region are an established cause; MLPA or array analysis of PAR1 is therefore required rather than optional.

genetic testing NCIT:C15709

Show evidence (1 reference)

PMID:20301394 SUPPORT Human Clinical

"The diagnosis of SHOX deficiency is established in a proband with either a pathogenic SHOX variant or a deletion, duplication, or insertion that can encompass the SHOX coding region and/or the enhancer region regulating SHOX expression."

States that enhancer-region defects establish the diagnosis equally with coding-region variants, which is the operational point of this section.

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Prevalence

1

Worldwide

Cases In Literature ≤0.1 per 100,000 Ultra Rare

Fewer than one hundred cases are documented in the literature. No population-based estimate exists; LMD is markedly rarer than Leri-Weill dyschondrosteosis because it requires two SHOX-region defects. The ULTRA_RARE band and the sub-1-per-million upper bound are inferred from the cumulative case count rather than measured against a denominator.

Show evidence (1 reference)

PMID:42553923 SUPPORT Human Clinical

"LMD remains an exceedingly rare condition, with fewer than one hundred cases documented in the medical literature"

Gives the cumulative published case count, the basis for the rarity band recorded here.

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Differential Diagnoses

3

Conditions with similar clinical presentations that must be differentiated from Langer Mesomelic Dysplasia:

Leri-Weill dyschondrosteosis

Overlapping Features The heterozygous counterpart, caused by the same alleles at half the dose. Milder mesomelic shortening with Madelung deformity, and no ulnar or fibular aplasia. Both parents of an LMD proband typically have LWD.

Robinow syndrome

Overlapping Features Also mesomelic, but adds genital hypoplasia and the fetal-facies gestalt, which SHOX deficiency does not produce.

Acromesomelic dysplasia, Maroteaux type

Overlapping Features Combined middle- and distal-segment shortening from NPR2 defects; the acral component and the normal ulna distinguish it.

{ }

Source YAML

click to show

name: Langer Mesomelic Dysplasia
synonyms:
- Mesomelic dysplasia (Langer type), SHOX-related
- Langer mesomelic dwarfism
- LMD
- mesomelic dwarfism of the hypoplastic ulna, fibula and mandible type
creation_date: "2026-08-27T00:00:00Z"
category: Mendelian
description: >-
  Langer mesomelic dysplasia is the severe, biallelic end of the SHOX deficiency
  spectrum: complete rather than partial loss of the short-stature homeobox
  transcription factor encoded in pseudoautosomal region 1 of the sex
  chromosomes. Where heterozygous SHOX loss produces Leri-Weill
  dyschondrosteosis — moderate mesomelic shortening with Madelung deformity —
  homozygous or compound heterozygous loss of SHOX or its flanking PAR1
  enhancers produces marked mesomelic dwarfism with severe hypoplasia or
  aplasia of the ulna and fibula, bowing of the radius and tibia, and mandibular
  hypoplasia. The relationship is dosage, not a different mechanism: LMD and LWD
  segregate in the same families, with the LMD probands homozygous for the very
  allele their LWD parents carry heterozygously.
disease_term:
  preferred_term: Langer mesomelic dysplasia
  term:
    id: MONDO:0009588
    label: Langer mesomelic dysplasia
parents:
- Skeletal Dysplasia
- Mesomelic Dysplasia
- SHOX-related skeletal dysplasia
notes: >-
  Scope. This entry covers the biallelic (homozygous, compound heterozygous, or
  hemizygous) end of the SHOX deficiency spectrum. The heterozygous Leri-Weill
  presentation is curated separately as ``Leri-Weill_Dyschondrosteosis``, and
  SHOX-deficient short stature without mesomelia or Madelung deformity is
  modelled in neither entry as a primary scope. Splitting LMD from LWD follows
  both the ISDS Nosology, which lists them as separate rows, and MONDO; the two
  entries cross-reference each other rather than one carrying the other as a
  subtype, because the phenotypic gap between them is large enough that a reader
  looking up LMD should not have to reconstruct it from a parent entry's
  qualifiers.

  Cognition. Intellect is typically normal in LMD, and reported intellectual
  disability has been attributed to large deletions extending beyond PAR1 into
  contiguous genes rather than to SHOX nullizygosity itself (PMID:42553923: "
  Cognitive development and intellectual potential typically fall within the
  normal range"). No phenotype entry is curated for this, because HPO codes
  abnormalities and a normal finding has no appropriate term; the point belongs
  in counselling when a large deletion is found.

  Two phenotypes are deliberately left unwired to the pathograph. Micrognathia
  and conductive hearing loss are both recorded features, but neither has a
  published developmental route from SHOX loss: SHOX has no described expression
  domain in the mandible or the middle ear, and the hearing loss comes from a
  single consanguineous cohort whose own authors could not separate a real
  phenotypic manifestation from a coincidental finding. Drawing an edge to
  either would assert a mechanism nobody has shown.

  Deletions of the PAR1 enhancers downstream and upstream of SHOX cause the
  same disease as deletions of the coding region, so a negative SHOX
  coding-sequence result does not exclude the diagnosis. That is a curation
  point with direct diagnostic consequence and is recorded in the diagnosis
  section rather than only in prose here.
classifications:
  harrisons_chapter:
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
    notes: >-
      A Mendelian skeletal dysplasia; tagged on the genetics axis rather than to
      an organ-system chapter.
  isds_skeletal_category:
  - classification_value: mesomelic_and_rhizomesomelic_dysplasias
    notes: >-
      ISDS Nosology of Genetic Skeletal Disorders, 2023 revision (Unger et al.,
      PMID:36779427), group 15 "Mesomelic and rhizo-mesomelic dysplasias", row
      NOS 15-0020, listed as "Mesomelic dysplasia (Langer type), SHOX-related"
      (MIM 249700, pseudoautosomal recessive). The immediately preceding row,
      NOS 15-0010, is the heterozygous Leri-Weill counterpart, curated here as a
      separate dismech entry. The 2019 revision (Mortier et al., PMID:31633310)
      numbered the same group 17.
prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  rate_high: 0.1
  notes: >-
    Fewer than one hundred cases are documented in the literature. No
    population-based estimate exists; LMD is markedly rarer than Leri-Weill
    dyschondrosteosis because it requires two SHOX-region defects. The
    ULTRA_RARE band and the sub-1-per-million upper bound are inferred from the
    cumulative case count rather than measured against a denominator.
  evidence:
  - reference: PMID:42553923
    reference_title: "Langer mesomelic dysplasia as a rare manifestation of SHOX deficiency: a narrative review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      LMD remains an exceedingly rare condition, with fewer than one hundred
      cases documented in the medical literature
    explanation: >-
      Gives the cumulative published case count, the basis for the rarity band
      recorded here.
inheritance:
- name: Pseudoautosomal recessive
  inheritance_term:
    preferred_term: Pseudoautosomal recessive inheritance
    term:
      id: HP:0034341
      label: Pseudoautosomal recessive inheritance
  penetrance: COMPLETE
  description: >-
    SHOX lies in pseudoautosomal region 1, which escapes X inactivation and
    recombines between X and Y, so SHOX alleles follow autosomal rules in both
    sexes. LMD requires two defective SHOX alleles. The characteristic pedigree
    is two LWD parents with a 25% risk per pregnancy of an LMD child;
    consanguinity and pseudodominant transmission (an affected parent mating
    with a heterozygous carrier) both occur.
  evidence:
  - reference: PMID:20301394
    reference_title: "SHOX Deficiency Disorders."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      If both parents have SHOX deficiency, the offspring have a 50% chance of
      having a SHOX deficiency disorder, a 25% chance of having Langer type of
      mesomelic dwarfism, and a 25% chance of having neither condition.
    explanation: >-
      GeneReviews states the recurrence arithmetic that defines the recessive
      relationship of LMD to heterozygous SHOX deficiency.
  - reference: PMID:12116253
    reference_title: "Pseudodominant inheritance of Langer mesomelic dysplasia caused by a SHOX homeobox missense mutation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The same mutation was present in the heterozygous state in the proband's
      father and in the maternal grandmother, both of whom had features of LWD.
    explanation: >-
      Documents the same allele producing LWD when heterozygous and LMD when
      homozygous within one pedigree — the clearest possible demonstration of
      the dosage relationship.
pathophysiology:
- name: Complete Loss of SHOX Transcription Factor Activity
  biological_scale: MOLECULAR
  genes:
  - preferred_term: SHOX
    term:
      id: hgnc:10853
      label: SHOX
  genetic_context:
    gene:
      preferred_term: SHOX
      term:
        id: hgnc:10853
        label: SHOX
    allele_type: SHOX coding deletion, PAR1 enhancer deletion, or homeodomain missense
    zygosity: HOMOZYGOUS
    functional_impact_category: LOSS_OF_FUNCTION
  description: >-
    SHOX encodes a paired-related homeodomain transcription factor expressed in
    growth plate chondrocytes. In LMD both alleles are defective, by any of
    three routes that converge on absent functional protein: deletion of the
    coding region, homozygous deletion of the PAR1 enhancers that drive SHOX
    expression in the limb, or homeodomain missense substitutions that impair
    DNA binding and nuclear import. The homozygous or hemizygous defect reported
    in the defining series lay in exon 6a, implicating the SHOXa isoform
    specifically as the one required for normal skeletal development.
  molecular_functions:
  - preferred_term: SHOX sequence-specific DNA binding
    modifier: LOSS_OF_FUNCTION
    term:
      id: GO:0000981
      label: DNA-binding transcription factor activity, RNA polymerase II-specific
  evidence:
  - reference: PMID:12116254
    reference_title: "Complete SHOX deficiency causes Langer mesomelic dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      SHOX abnormalities were detected in all five probands. One was a
      homozygote or hemizygote and two were compound heterozygotes.
    explanation: >-
      Establishes biallelic SHOX defects in every proband of the defining
      series, which is the claim of this node.
  - reference: PMID:12116254
    reference_title: "Complete SHOX deficiency causes Langer mesomelic dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The homozygous or hemizygous mutation was in exon 6a, implying that the
      SHOXa isoform is essential for normal skeletal development.
    explanation: >-
      Supports the isoform-specific requirement asserted in this node's
      description.
  - reference: PMID:12116253
    reference_title: "Pseudodominant inheritance of Langer mesomelic dysplasia caused by a SHOX homeobox missense mutation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This C to T transition is predicted to cause an arginine to cysteine amino
      acid change in a highly conserved region of the recognition helix of the
      homeodomain, which may reduce the stability of the interaction between the
      SHOX protein and its target DNA.
    explanation: >-
      Supplies the molecular consequence of the missense route to complete
      deficiency: impaired homeodomain-DNA interaction. The source hedges
      ("predicted", "may"), and this node inherits that hedge.
  downstream:
  - target: Loss of SHOX Chondrogenic Target Regulation
    causal_link_type: DIRECT
    description: >-
      Absent SHOX protein removes the transcriptional program it drives.
- name: Loss of SHOX Chondrogenic Target Regulation
  biological_scale: MOLECULAR
  description: >-
    SHOX does not act alone on one target. It directly induces NPPB (natriuretic
    peptide B / BNP), whose co-expression with SHOX in prehypertrophic and
    hypertrophic chondrocytes places the pair in growth plate regulation; it
    interacts with SOX5 and SOX6 to regulate aggrecan synthesis and cartilage
    matrix assembly; and in a chondrogenic context it represses FGFR3, itself a
    negative regulator of endochondral growth. Losing SHOX therefore removes a
    growth-promoting input and simultaneously de-represses a growth-inhibiting
    one — a plausible reason the biallelic phenotype is disproportionately
    severe rather than simply twice as bad.
  biological_processes:
  - preferred_term: Regulation of chondrocyte gene expression by SHOX
    modifier: DECREASED
    term:
      id: GO:0006357
      label: regulation of transcription by RNA polymerase II
  evidence:
  - reference: PMID:42553923
    reference_title: "Langer mesomelic dysplasia as a rare manifestation of SHOX deficiency: a narrative review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The SHOX protein also directly induces transcription of the NPPB gene,
      encoding the natriuretic peptide BNP, a direct SHOX target whose
      co-expression with SHOX in prehypertrophic and hypertrophic chondrocytes
      implicates this axis in growth plate regulation
    explanation: >-
      Establishes NPPB as a direct SHOX target expressed in the relevant
      chondrocyte populations.
  - reference: PMID:42553923
    reference_title: "Langer mesomelic dysplasia as a rare manifestation of SHOX deficiency: a narrative review."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Given that the FGFR3 protein is a known negative regulator of endochondral
      bone growth, this SHOX protein-mediated repression is likely critical for
      growth homeostasis in mesomelic segments.
    explanation: >-
      Supports the FGFR3 de-repression limb of this node. The source itself
      hedges ("likely"), and the repression was shown in chicken micromass
      culture rather than human cartilage, so this is recorded as PARTIAL
      IN_VITRO rather than as an established human mechanism.
  downstream:
  - target: Disorganized Growth Plate Chondrocyte Maturation
    causal_link_type: DIRECT
    description: >-
      Loss of the SHOX target program is what the disorganized growth plate is
      downstream of.
- name: Zeugopod-Restricted SHOX Expression Domain
  biological_scale: TISSUE
  description: >-
    Why the middle limb segment and not the whole limb. In human embryos SHOX
    and its paralog SHOX2 occupy complementary limb domains: SHOX in the
    zeugopod (forearm, lower leg), SHOX2 more proximally in the stylopod. The
    paralog therefore cannot compensate where SHOX is lost, and the deficit is
    confined to the segment SHOX alone patterns. This is the anatomical
    explanation of "mesomelic", and it is a positional argument rather than a
    severity one.
  biological_processes:
  - preferred_term: limb development
    modifier: DECREASED
    term:
      id: GO:0060173
      label: limb development
  evidence:
  - reference: PMID:42553923
    reference_title: "Langer mesomelic dysplasia as a rare manifestation of SHOX deficiency: a narrative review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In human embryos, SHOX and SHOX2 display complementary expression profiles
      during limb development: SHOX is detected in the middle portion of the
      limb corresponding to the mesomelic segments, whereas SHOX2 is expressed
      more proximally
    explanation: >-
      Establishes the complementary expression domains that make the phenotype
      segment-specific.
  - reference: PMID:42553923
    reference_title: "Langer mesomelic dysplasia as a rare manifestation of SHOX deficiency: a narrative review."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      conditional Shox2 inactivation in murine limbs, a species that has lost
      the SHOX gene during evolution, leads to severe stylopodial (humerus,
      femur) shortening, with relative sparing of the zeugopod, confirming the
      complementary segmental roles of these paralogs
    explanation: >-
      The reciprocal experiment: removing the proximal paralog produces the
      proximal phenotype, corroborating the segmental division of labour.
  downstream:
  - target: Disorganized Growth Plate Chondrocyte Maturation
    causal_link_type: DIRECT
    description: >-
      This node is a precondition, not a consequence: the expression domain
      pre-exists the mutation and is what confines the growth-plate
      disorganization to zeugopodal cartilage. It has no incoming edge for that
      reason.
  - target: Severe Mesomelic Limb Shortening
    causal_link_type: DIRECT
    description: >-
      The segment SHOX patterns alone is the segment that fails.
- name: Disorganized Growth Plate Chondrocyte Maturation
  biological_scale: CELLULAR
  description: >-
    SHOX-deficient growth plates lose their normal parallel columnar arrangement
    of chondrocytes, with tandem stacking replaced by a side-by-side
    arrangement, an expanded hypertrophic layer, and evidence of abnormal
    endochondral ossification. Unusually for a disorder this rare, the lesion has
    been described in LMD tissue itself and not only inferred from the
    heterozygous state: fetal growth plates from terminated LMD pregnancies show
    shortened, side-by-side chondrocyte columns in the proliferative zone and
    enlarged reserve-zone chondrocytes, with mutant SHOX protein still detectable
    across all three zones.
  cell_types:
  - preferred_term: Growth plate chondrocyte
    term:
      id: CL:1000217
      label: growth plate cartilage chondrocyte
  - preferred_term: Hypertrophic chondrocyte
    term:
      id: CL:0000743
      label: hypertrophic chondrocyte
  biological_processes:
  - preferred_term: Growth plate chondrocyte differentiation
    modifier: DECREASED
    term:
      id: GO:0003418
      label: growth plate cartilage chondrocyte differentiation
  - preferred_term: Endochondral bone morphogenesis
    modifier: DECREASED
    term:
      id: GO:0060350
      label: endochondral bone morphogenesis
  evidence:
  - reference: PMID:11677662
    reference_title: "Histopathological analysis of Leri-Weill dyschondrosteosis: disordered growth plate."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A widespread disorganisation of physeal anatomy was revealed with
      disruption of the normal parallel columnar arrangement of chondrocytes.
      Tandem stacking of maturing chondrocytes within columns was replaced by
      a side-by-side arrangement.
    explanation: >-
      Direct human growth-plate histopathology of SHOX deficiency. The material
      is from heterozygous LWD patients; the LMD-specific fetal histology in the
      next item shows the same columnar disorganization.
  - reference: PMID:42553923
    reference_title: "Langer mesomelic dysplasia as a rare manifestation of SHOX deficiency: a narrative review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      significant cellular disorganization was evident in the proliferative
      zone, where chondrocyte columns were shortened and stacked side-by-side
      rather than in a normal longitudinal orientation. Additionally,
      enlargement of chondrocytes was observed in the reserve zone.
    explanation: >-
      Histopathology from LMD fetal growth plates specifically, which is what
      makes this node an observation in the disease rather than a transfer from
      the heterozygous state.
  - reference: PMID:25110390
    reference_title: "Skeletal Deformity Associated with SHOX Deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      histopathological analyses showed a disrupted columnar arrangement of
      chondrocytes and an expanded hypertrophic layer of the growth plate.
      Recent studies have suggested that perturbed programmed cell death of
      hypertrophic chondrocytes may underlie the skeletal changes related to
      SHOX deficiency.
    explanation: >-
      Review confirming the growth-plate lesion across SHOX deficiency and
      naming hypertrophic chondrocyte apoptosis as a candidate underlying
      process.
  downstream:
  - target: Severe Mesomelic Limb Shortening
    causal_link_type: DIRECT
    description: >-
      Failure of ordered chondrocyte maturation truncates longitudinal growth of
      the middle limb segment.
- name: Severe Mesomelic Limb Shortening
  biological_scale: ORGANISM
  description: >-
    The clinical endpoint: the middle limb segments are the most severely
    affected, with the ulna and fibula hypoplastic or absent and the radius and
    tibia short and bowed. Because both alleles are lost, the shortening is
    substantially more severe than in Leri-Weill dyschondrosteosis and is
    already detectable prenatally.
  evidence:
  - reference: PMID:12116254
    reference_title: "Complete SHOX deficiency causes Langer mesomelic dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These findings confirm clinical inferences that Langer mesomelic dysplasia
      is the homozygous form of Leri-Weill dyschondrosteosis and add to our
      understanding of genotype/phenotype relationships in SHOX deficiency
      disorders.
    explanation: >-
      Establishes the dosage relationship between the two entities, which is
      what makes this node's severity claim mechanistic rather than descriptive.
  downstream:
  - target: Severe Mesomelia
    causal_link_type: DIRECT
    description: >-
      The zeugopod is where SHOX alone patterns growth, so it is the segment
      that fails.
  - target: Disproportionate Short Stature
    causal_link_type: DIRECT
    description: >-
      Stature loss is limb-restricted, which is why the trunk and pelvis remain
      normally proportioned.
  - target: Ulnar Hypoplasia
    causal_link_type: DIRECT
    description: >-
      The ulna is the zeugopod bone that fails most severely, often losing its
      distal epiphysis.
  - target: Fibular Hypoplasia
    causal_link_type: DIRECT
    description: >-
      The lower-limb counterpart of the ulnar lesion, with the fibular head
      ossification centre often absent.
  - target: Radial Bowing
    causal_link_type: DIRECT
    description: >-
      Unequal growth failure between the paired forearm bones bows the radius.
  - target: Madelung Deformity
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Where distal radial growth fails asymmetrically against the ulna, the same
      wrist geometry as in Leri-Weill dyschondrosteosis results — but the
      biallelic lesion distorts the whole zeugopod, so the classic deformity is
      often obscured rather than accentuated.
  - target: Genu Valgum
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Valgus at the knee and ankle follows from the tibia and fibula being
      shortened by different amounts, not from a primary joint lesion.
phenotypes:
- category: Skeletal
  name: Severe Mesomelia
  description: >-
    Marked shortening of the forearms and lower legs, the defining feature and
    substantially more severe than in the heterozygous Leri-Weill presentation.
    Radiographs show dysplastic and hypoplastic change in all long bones with
    the mesomelic segments disproportionately affected.
  phenotype_term:
    preferred_term: Mesomelia
    term:
      id: HP:0003027
      label: Mesomelia
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:42553923
    reference_title: "Langer mesomelic dysplasia as a rare manifestation of SHOX deficiency: a narrative review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Radiographic findings demonstrate significant dysplastic and hypoplastic
      changes in all long bones, with a characteristic and disproportionate
      mesomelic shortening of the forearms and lower legs. Defective
      ossification is particularly prominent in the distal ulna and proximal
      fibula
    explanation: >-
      States the radiographic distribution of the shortening and where
      ossification fails most.
- category: Skeletal
  name: Disproportionate Short Stature
  description: >-
    Severe short stature with a disproportionately short middle limb segment;
    LMD is a mesomelic dwarfism rather than a proportionate growth failure. The
    cranium, chest, spine, and pelvis are typically normally proportioned, which
    is what makes the disproportion so visually striking.
  phenotype_term:
    preferred_term: Disproportionate short stature
    term:
      id: HP:0003498
      label: Disproportionate short stature
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:42553923
    reference_title: "Langer mesomelic dysplasia as a rare manifestation of SHOX deficiency: a narrative review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Reported cases of LMD involve various degrees of limb skeletal
      abnormalities, whereas the cranium, chest, spine, and pelvis typically
      show normal proportions
    explanation: >-
      Establishes that the growth deficit is limb-restricted, which is the
      content of "disproportionate" here.
  - reference: PMID:20301394
    reference_title: "SHOX Deficiency Disorders."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      a 25% chance of having Langer type of mesomelic dwarfism
    explanation: >-
      GeneReviews names the entity as a mesomelic dwarfism.
- category: Skeletal
  name: Ulnar Hypoplasia
  description: >-
    The ulna is bowed and hypoplastic and often lacks its distal epiphysis;
    aplasia occurs. With the fibula, it is the bone whose near-absence gives the
    disorder its descriptive name.
  phenotype_term:
    preferred_term: Hypoplasia of the ulna
    term:
      id: HP:0003022
      label: Hypoplasia of the ulna
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:42553923
    reference_title: "Langer mesomelic dysplasia as a rare manifestation of SHOX deficiency: a narrative review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In the upper limbs, both the radius and ulna exhibit marked deformities;
      the ulna is typically bowed and hypoplastic, often lacking the distal
      epiphysis.
    explanation: >-
      Describes the ulnar lesion, including the absent distal epiphysis.
- category: Skeletal
  name: Fibular Hypoplasia
  description: >-
    The fibula is often rudimentary and proximally shortened, and the
    ossification centre for the fibular head may be absent.
  phenotype_term:
    preferred_term: Fibular hypoplasia
    term:
      id: HP:0003038
      label: Fibular hypoplasia
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:42553923
    reference_title: "Langer mesomelic dysplasia as a rare manifestation of SHOX deficiency: a narrative review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      whereas the fibula is often rudimentary and proximally shortened. The
      ossification center for the fibular head may be absent
    explanation: >-
      Describes the fibular lesion and the absent ossification centre.
- category: Skeletal
  name: Radial Bowing
  description: >-
    The radius shows varying degrees of bowing and may carry a Madelung-type
    deformity, which is variable in LMD and may be severe, mild, or absent —
    unlike in Leri-Weill dyschondrosteosis, where it is the diagnostic sign.
  phenotype_term:
    preferred_term: Radial bowing
    term:
      id: HP:0002986
      label: Radial bowing
  frequency: FREQUENT
  evidence:
  - reference: PMID:42553923
    reference_title: "Langer mesomelic dysplasia as a rare manifestation of SHOX deficiency: a narrative review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The radius demonstrates varying degrees of bowing and may be associated
      with Madelung-type deformity, although this feature shows considerable
      variability: it may be severe, mild, or even absent in individual
      patients
    explanation: >-
      Supports both the bowing and the explicit variability of the Madelung
      component in this disorder.
- category: Skeletal
  name: Genu Valgum
  description: >-
    Valgus deformity at the knees and ankles, arising from the length
    disproportion between tibia and fibula rather than from a primary joint
    abnormality. It is often the complaint that brings the patient to orthopedic
    attention.
  phenotype_term:
    preferred_term: Genu valgum
    term:
      id: HP:0002857
      label: Genu valgum
  frequency: FREQUENT
  evidence:
  - reference: PMID:42553923
    reference_title: "Langer mesomelic dysplasia as a rare manifestation of SHOX deficiency: a narrative review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The disproportion between tibial and fibular lengths contributes to
      characteristic valgus deformities at the knees (genu valgum) and ankles,
      which may be the presenting feature leading to orthopedic consultation
    explanation: >-
      Gives both the mechanism of the valgus deformity and its role as a
      presenting complaint.
- category: Skeletal
  name: Madelung Deformity
  description: >-
    A Madelung-type wrist deformity may accompany the radial bowing, but unlike
    in Leri-Weill dyschondrosteosis — where it is the diagnostic sign — it is
    variable here and may be severe, mild, or absent. Its absence therefore does
    not argue against LMD.
  phenotype_term:
    preferred_term: Madelung deformity
    term:
      id: HP:0003067
      label: Madelung deformity
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:42553923
    reference_title: "Langer mesomelic dysplasia as a rare manifestation of SHOX deficiency: a narrative review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The radius demonstrates varying degrees of bowing and may be associated
      with Madelung-type deformity, although this feature shows considerable
      variability: it may be severe, mild, or even absent in individual
      patients
    explanation: >-
      Supports the feature's occurrence while explicitly refuting its constancy,
      which is why the frequency is OCCASIONAL and the evidence PARTIAL.
- category: Craniofacial
  name: Micrognathia
  description: >-
    Mandibular hypoplasia was part of Langer's original description and survives
    in the disorder's descriptive synonym, but later series find it
    inconsistently present. It should not be treated as a required feature.
  phenotype_term:
    preferred_term: Micrognathia
    term:
      id: HP:0000347
      label: Micrognathia
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:42553923
    reference_title: "Langer mesomelic dysplasia as a rare manifestation of SHOX deficiency: a narrative review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Although originally considered a defining feature of LMD (Langer, 1967),
      hypoplastic mandible is now recognized as inconsistently present
    explanation: >-
      Supports the feature's occurrence while refuting its status as a defining
      criterion, which is why the frequency here is OCCASIONAL rather than
      VERY_FREQUENT.
- category: Auditory
  name: Conductive Hearing Loss
  description: >-
    Bilateral conductive hearing loss was found in two of four LMD patients in a
    Turkish consanguineous cohort. Whether this belongs to SHOX deficiency or is
    a coincidental finding in that family is unresolved, so it is curated as a
    reported association rather than an established feature.
  phenotype_term:
    preferred_term: Conductive hearing impairment
    term:
      id: HP:0000405
      label: Conductive hearing impairment
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:42553923
    reference_title: "Langer mesomelic dysplasia as a rare manifestation of SHOX deficiency: a narrative review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Whether this represents a rare phenotypic manifestation of SHOX deficiency
      or a coincidental finding in a consanguineous family remains unclear
    explanation: >-
      The source's own statement of the uncertainty, which is why this phenotype
      is recorded as PARTIAL rather than SUPPORT.
genetic:
- name: SHOX
  gene_term:
    preferred_term: SHOX
    term:
      id: hgnc:10853
      label: SHOX
  relationship_type: CAUSATIVE
  notes: >-
    Short stature homeobox, in pseudoautosomal region 1 at Xp22.33/Yp11.32.
    Biallelic defects cause LMD; heterozygous defects cause Leri-Weill
    dyschondrosteosis or isolated short stature. The allelic spectrum spans
    whole-gene deletions, deletions of the downstream and upstream PAR1
    enhancers with an intact coding region, homeodomain point mutations, and
    canonical splice-site variants.
    Enhancer deletions matter operationally: a test that sequences only the SHOX
    coding region will miss them.
  evidence:
  - reference: PMID:12116254
    reference_title: "Complete SHOX deficiency causes Langer mesomelic dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      SHOX abnormalities were detected in all five probands. One was a
      homozygote or hemizygote and two were compound heterozygotes.
    explanation: >-
      Establishes SHOX as causative with biallelic defects in every proband
      studied.
  - reference: PMID:23883335
    reference_title: "Langer mesomelic dysplasia in early fetuses: two cases and a literature review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      a homozygous deletion of the 3' enhancer of the SHOX gene, and
      consanguineous parents affected by Léri-Weill dyschondrosteosis
    explanation: >-
      Documents the enhancer-deletion route to LMD with an intact coding region,
      the allele class most easily missed by coding-only testing.
  - reference: PMID:41042407
    reference_title: "Exploring genotype-phenotype correlation of a novel SHOX gene splicing variant: Langer mesomelic dysplasia or idiopathic short stature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A novel SHOX gene splice donor variant (c.486 + 2T > C) was found in
      homozygous form in individuals with LMD, and in heterozygous form in
      individuals with ISS.
    explanation: >-
      One allele, two doses, two diagnoses within a single family — the cleanest
      available demonstration that the LMD/ISS distinction is gene dosage rather
      than allele identity. It also adds splice-site variants to the allelic
      spectrum alongside deletions and missense.
  - reference: PMID:41042407
    reference_title: "Exploring genotype-phenotype correlation of a novel SHOX gene splicing variant: Langer mesomelic dysplasia or idiopathic short stature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The mutation segregated perfectly with ISS, LMD, and normal stature in
      this family.
    explanation: >-
      Perfect co-segregation across three phenotype classes in one pedigree,
      which is what makes the dosage reading rather than a chance association.
diagnosis:
- name: Radiographic and Clinical Recognition
  description: >-
    Suspected from severe mesomelic dwarfism with hypoplastic or absent ulna and
    fibula, short bowed radius and tibia, and mandibular hypoplasia. Because the
    deformity is already present in the fetus, LMD can be recognized on prenatal
    ultrasound and confirmed by fetal radiography and autopsy where a pregnancy
    is not continued. A family history of Leri-Weill dyschondrosteosis in both
    parents is a strong pointer.
  diagnosis_term:
    preferred_term: diagnostic radiography
    term:
      id: NCIT:C17369
      label: Imaging Procedure
  evidence:
  - reference: PMID:23883335
    reference_title: "Langer mesomelic dysplasia in early fetuses: two cases and a literature review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A competent pathologist could provide important diagnostic information,
      orienting or confirming the echographic or genetic suspect
    explanation: >-
      Supports the role of fetal pathological and radiographic assessment
      alongside ultrasound and molecular testing.
- name: Molecular Confirmation of Biallelic SHOX/PAR1 Defect
  description: >-
    Diagnosis is confirmed by demonstrating two defective SHOX alleles. Testing
    must cover the PAR1 enhancer regions as well as the coding sequence, since
    homozygous enhancer deletions with an intact SHOX coding region are an
    established cause; MLPA or array analysis of PAR1 is therefore required
    rather than optional.
  diagnosis_term:
    preferred_term: genetic testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  evidence:
  - reference: PMID:20301394
    reference_title: "SHOX Deficiency Disorders."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The diagnosis of SHOX deficiency is established in a proband with either a
      pathogenic SHOX variant or a deletion, duplication, or insertion that can
      encompass the SHOX coding region and/or the enhancer region regulating
      SHOX expression.
    explanation: >-
      States that enhancer-region defects establish the diagnosis equally with
      coding-region variants, which is the operational point of this section.
differential_diagnoses:
- name: Leri-Weill dyschondrosteosis
  description: >-
    The heterozygous counterpart, caused by the same alleles at half the dose.
    Milder mesomelic shortening with Madelung deformity, and no ulnar or fibular
    aplasia. Both parents of an LMD proband typically have LWD.
- name: Robinow syndrome
  description: >-
    Also mesomelic, but adds genital hypoplasia and the fetal-facies gestalt,
    which SHOX deficiency does not produce.
- name: Acromesomelic dysplasia, Maroteaux type
  description: >-
    Combined middle- and distal-segment shortening from NPR2 defects; the acral
    component and the normal ulna distinguish it.
treatments:
- name: Recombinant Growth Hormone Therapy
  description: >-
    rhGH is licensed and effective for SHOX-deficient short stature, with a
    reported final-height gain of 7 to 10 cm — but that evidence is entirely
    from heterozygous patients. In LMD the one documented treated case, an
    individual with combined LMD and Turner syndrome, showed a biochemical
    response with rising IGF-1 and no height-velocity response at all, with the
    height deficit widening over four years. Complete SHOX deficiency plausibly
    removes the growth plate substrate on which GH acts, so the extrapolation
    from LWD is not merely unproven but has been contradicted once. Offer it, if
    at all, with that explicitly on the table.
  therapeutic_modality: PROTEIN_REPLACEMENT
  treatment_term:
    preferred_term: Growth hormone therapy
    term:
      id: NCIT:C15599
      label: Hormone Replacement Therapy
    therapeutic_agent:
    - preferred_term: recombinant human growth hormone
      term:
        id: NCIT:C837
        label: Somatropin
  target_mechanisms:
  - target: Disorganized Growth Plate Chondrocyte Maturation
    description: >-
      Acts on the growth plate that the SHOX lesion disorganizes, but through a
      SHOX-independent axis. It does not restore SHOX target regulation, which is
      why the height gain is partial in a complete-loss genotype.
  evidence:
  - reference: PMID:42553923
    reference_title: "Langer mesomelic dysplasia as a rare manifestation of SHOX deficiency: a narrative review."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In particular, GH therapy failed to produce growth acceleration in a
      documented case involving a combination of LMD and Turner syndrome.
    explanation: >-
      The single reported LMD treatment experience is a negative result, which
      is why this evidence item is REFUTE rather than SUPPORT.
  - reference: PMID:42553923
    reference_title: "Langer mesomelic dysplasia as a rare manifestation of SHOX deficiency: a narrative review."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The authors concluded that GH therapy may not be beneficial in the setting
      of complete SHOX deficiency, although no worsening of the skeletal
      deformities was observed
    explanation: >-
      States the conclusion drawn from that case, including the reassurance that
      treatment did not make the skeletal phenotype worse.
  - reference: PMID:20301394
    reference_title: "SHOX Deficiency Disorders."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      For prepubertal children with SHOX-deficient short stature, recombinant
      human growth hormone (rhGH therapy) (dose 50 µg/kg body weight/day) should
      be offered. The therapeutic effect is a gain in final height of 7 to 10
      cm.
    explanation: >-
      The recommendation and effect size that would be extrapolated to LMD.
      PARTIAL because the population is the heterozygous spectrum, not LMD.
  - reference: PMID:23720786
    reference_title: "GH treatment to final height produces similar height gains in patients with SHOX deficiency and Turner syndrome: results of a multicenter trial."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Short-statured prepubertal patients with genetically confirmed SHOX
      deficiency (n = 49) or Turner syndrome (n = 24) who participated in the
      extension.
    explanation: >-
      Names the trial population explicitly, which is what makes the
      extrapolation to LMD visible as an extrapolation.
- name: Orthopedic Surgery for Limb Deformity
  description: >-
    Corrective and lengthening procedures for the forearm and lower leg
    deformity. Operative decisions in LMD are harder than in LWD because the
    ulna and fibula may be largely absent rather than merely deformed.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: orthopedic surgical procedure
    term:
      id: NCIT:C16186
      label: Orthopedic Surgical Procedure
  target_mechanisms:
  - target: Severe Mesomelic Limb Shortening
    description: >-
      Addresses the established limb anatomy. Purely anatomical correction; the
      upstream chondrogenic defect is unmodified.
  evidence:
  - reference: PMID:20301394
    reference_title: "SHOX Deficiency Disorders."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Different operative procedures have been attempted to decrease pain and
      restore wrist function.
    explanation: >-
      GeneReviews describes operative management within SHOX deficiency, though
      for the LWD Madelung deformity rather than the LMD long-bone deficiency;
      recorded as PARTIAL for that reason.
- name: Genetic Counseling
  action_category: COUNSELING_INFORMATIONAL
  description: >-
    Counseling is unusual here because the parents are themselves usually
    affected. Two LWD parents carry a 25% recurrence risk per pregnancy for LMD
    and a 50% risk for LWD, so the counseling conversation is about a spectrum
    of outcomes rather than affected-versus-unaffected.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: genetic counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:20301394
    reference_title: "SHOX Deficiency Disorders."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      If both parents have SHOX deficiency, the offspring have a 50% chance of
      having a SHOX deficiency disorder, a 25% chance of having Langer type of
      mesomelic dwarfism, and a 25% chance of having neither condition.
    explanation: >-
      Supplies the exact recurrence arithmetic this section describes.
discussions:
- discussion_id: no_mouse_shox_ortholog
  kind: HUMAN_MODEL_MISMATCH
  prompt: >-
    Can any rodent model be informative about SHOX loss, given that the mouse
    genome has no SHOX ortholog at all?
  attaches_to:
  - pathophysiology#Complete Loss of SHOX Transcription Factor Activity
  rationale: >-
    SHOX was lost from the rodent lineage; the mouse carries only the paralog
    Shox2, which has a different expression domain (proximal rather than middle
    limb segment). So the standard route for validating a transcription factor's
    developmental role — a knockout mouse — is unavailable for this disease, and
    the mechanism curated here rests entirely on human genetics and human growth
    plate histopathology. This is a structural limitation on the evidence, not a
    gap that more mouse work would close, and it is why the entry carries no
    ``animal_models`` section.
- discussion_id: gh_efficacy_in_complete_shox_deficiency
  kind: KNOWLEDGE_GAP
  prompt: >-
    Does recombinant growth hormone produce any height gain in complete
    (biallelic) SHOX deficiency, or does the licensed benefit in heterozygous
    SHOX deficiency simply not transfer?
  attaches_to:
  - treatments#Recombinant Growth Hormone Therapy
  rationale: >-
    The evidence base is asymmetric in a way that matters at the bedside:
    randomized trial data in heterozygous SHOX deficiency versus a single
    reported LMD case in which GH produced an IGF-1 response and no growth. One
    negative case cannot settle the question, but it is the only LMD-specific
    datum there is, and it points the opposite way from the licensed indication.
    Because LMD numbers fewer than a hundred published cases, a trial is
    implausible; a pooled registry of treated patients is the realistic route.
- discussion_id: prenatal_recognition_of_lmd
  kind: KNOWLEDGE_GAP
  prompt: >-
    How early and how reliably can LMD be distinguished on prenatal ultrasound
    from the other causes of severe fetal limb shortening?
  attaches_to:
  - diagnosis#Radiographic and Clinical Recognition
  rationale: >-
    Sonographic suspicion has been reported as early as 12+3 weeks, but the
    published prenatal experience is dominated by families already known to
    carry SHOX defects, where the prior probability is high. The operating
    characteristics of fetal ultrasound for LMD in an unselected population with
    short fetal long bones are unknown, which is the situation in which the
    question is actually asked.
references:
- reference: PMID:20301394
  title: "SHOX Deficiency Disorders."
  tags:
  - GeneReviews
- reference: PMID:36779427
  title: "Nosology of genetic skeletal disorders: 2023 revision."

📚

References & Deep Research

References

2

PMID:20301394

SHOX Deficiency Disorders.

No top-level findings curated for this source.

PMID:36779427

Nosology of genetic skeletal disorders: 2023 revision.

No top-level findings curated for this source.

Langer Mesomelic Dysplasia

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