Omodysplasia is a rare skeletal dysplasia characterized by severe rhizomelic shortening of the limbs, particularly of the humeri and femora, with distal tapering giving a club-like long bone morphology. Craniofacial features include frontal bossing, depressed nasal bridge, short nose with anteverted nares, and a long philtrum. Two genetic forms are recognized: an autosomal recessive form (OMOD1) caused by loss-of-function mutations in GPC6 encoding glypican-6, a heparan sulfate proteoglycan that stimulates Hedgehog signaling in growth plate chondrocytes; and an autosomal dominant form (OMOD2) caused by heterozygous mutations in FZD2 encoding Frizzled-2, a Wnt receptor that mediates both canonical and non-canonical Wnt signaling in limb development. The recessive form is more severe with generalized limb shortening, while the dominant form shows preferential humeral involvement with relatively preserved stature.
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name: Omodysplasia
creation_date: "2026-04-02T12:00:00Z"
updated_date: "2026-04-19T02:26:30Z"
category: Mendelian
description: >
Omodysplasia is a rare skeletal dysplasia characterized by severe rhizomelic
shortening of the limbs, particularly of the humeri and femora, with distal
tapering giving a club-like long bone morphology. Craniofacial features include
frontal bossing, depressed nasal bridge, short nose with anteverted nares, and
a long philtrum. Two genetic forms are recognized: an autosomal recessive form
(OMOD1) caused by loss-of-function mutations in GPC6 encoding glypican-6, a
heparan sulfate proteoglycan that stimulates Hedgehog signaling in growth plate
chondrocytes; and an autosomal dominant form (OMOD2) caused by heterozygous
mutations in FZD2 encoding Frizzled-2, a Wnt receptor that mediates both
canonical and non-canonical Wnt signaling in limb development. The recessive
form is more severe with generalized limb shortening, while the dominant form
shows preferential humeral involvement with relatively preserved stature.
disease_term:
preferred_term: omodysplasia
term:
id: MONDO:0017136
label: omodysplasia
parents:
- Skeletal Dysplasia
- Rhizomelic Limb Shortening Syndrome
has_subtypes:
- name: OMOD1
display_name: Autosomal Recessive Omodysplasia (GPC6-related)
description: >
The recessive form is caused by biallelic loss-of-function mutations in GPC6.
It presents with severe generalized rhizomelic limb shortening affecting both
upper and lower extremities, facial dysmorphism, and variable developmental
delay. Fewer than 30 cases have been reported.
subtype_term:
preferred_term: autosomal recessive omodysplasia
term:
id: MONDO:0009779
label: autosomal recessive omodysplasia
- name: OMOD2
display_name: Autosomal Dominant Omodysplasia (FZD2-related)
description: >
The dominant form is caused by heterozygous mutations in FZD2. It is
characterized by predominantly humeral shortening with relatively normal
stature, short first metacarpals, and genitourinary anomalies. The phenotype
overlaps with autosomal dominant Robinow syndrome.
subtype_term:
preferred_term: autosomal dominant omodysplasia
term:
id: MONDO:0008123
label: autosomal dominant omodysplasia
inheritance:
- name: Autosomal recessive
inheritance_term:
preferred_term: Autosomal recessive inheritance
term:
id: HP:0000007
label: Autosomal recessive inheritance
description: >
Autosomal recessive omodysplasia is caused by biallelic mutations in GPC6,
including point mutations and larger genomic rearrangements. Parental
consanguinity is common among reported families.
evidence:
- reference: PMID:19481194
reference_title: "Mutations in the heparan-sulfate proteoglycan glypican 6 (GPC6) impair endochondral ossification and cause recessive omodysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
autosomal-recessive omodysplasia, a genetic condition characterized by
short-limbed short stature, craniofacial dysmorphism, and variable
developmental delay, maps to chromosome 13 (13q31.1-q32.2) and is caused
by point mutations or by larger genomic rearrangements in glypican 6 (GPC6)
explanation: >-
Identifies GPC6 as the causative gene for autosomal recessive omodysplasia
via linkage mapping and mutation analysis.
- name: Autosomal dominant
inheritance_term:
preferred_term: Autosomal dominant inheritance
term:
id: HP:0000006
label: Autosomal dominant inheritance
de_novo_rate: "majority"
description: >
Autosomal dominant omodysplasia is caused by heterozygous mutations in FZD2.
Most reported cases are de novo, with nonsense mutations in the C-terminal
Dishevelled-interacting domain representing a mutational hotspot.
evidence:
- reference: PMID:25759469
reference_title: "A mutation in FRIZZLED2 impairs Wnt signaling and causes autosomal dominant omodysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
We identified a de novo mutation in FRIZZLED2 (FZD2) in the proband and
her daughter that was not found in unaffected family members
explanation: >-
First identification of FZD2 as the causative gene for autosomal dominant
omodysplasia.
- reference: PMID:29383834
reference_title: "Nonsense mutations in FZD2 cause autosomal-dominant omodysplasia: Robinow syndrome-like phenotypes."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Molecular analysis identified a de novo, heterozygous, nonsense mutation
(c.1640C>A, p.S547*) in FZD2. The affected codon was next to the
previously reported mutation (p.Trp548*)
explanation: >-
Confirms recurrent de novo nonsense FZD2 mutations in the C-terminal
domain as the cause of autosomal dominant omodysplasia.
pathophysiology:
- name: GPC6 loss of function and impaired Hedgehog signaling
description: >
In the recessive form, loss-of-function mutations in GPC6 abolish the
heparan sulfate binding site and the GPI membrane anchor, eliminating
glypican-6 from the chondrocyte surface. GPC6 normally promotes Hedgehog
signaling by binding to Hedgehog ligand through its core protein and to
Patched-1 through its glycosaminoglycan chains, facilitating ligand-receptor
interaction at the primary cilium. Loss of GPC6 reduces Hedgehog signaling in
growth plate chondrocytes, impairing proliferative chondrocyte function and
endochondral ossification.
cell_types:
- preferred_term: Growth plate chondrocyte
term:
id: CL:1000217
label: growth plate cartilage chondrocyte
biological_processes:
- preferred_term: Endochondral ossification
term:
id: GO:0001958
label: endochondral ossification
modifier: DECREASED
- preferred_term: Smoothened signaling pathway
term:
id: GO:0007224
label: smoothened signaling pathway
modifier: DECREASED
gene:
preferred_term: GPC6
description: >-
Glypican-6, a GPI-anchored heparan sulfate proteoglycan expressed in
proliferative chondrocytes that stimulates Hedgehog signaling by
facilitating Hedgehog-Patched interaction at the primary cilium.
modifier: DECREASED
term:
id: hgnc:4454
label: GPC6
evidence:
- reference: PMID:19481194
reference_title: "Mutations in the heparan-sulfate proteoglycan glypican 6 (GPC6) impair endochondral ossification and cause recessive omodysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
All mutations cause truncation of the GPC6 protein and abolish both the
HS-binding site and the GPI-bearing membrane-associated domain, and thus
loss of function is predicted
explanation: >-
Demonstrates that all identified GPC6 mutations are loss-of-function,
truncating both the heparan sulfate binding and membrane anchor domains.
- reference: PMID:28696225
reference_title: "Glypican-6 promotes the growth of developing long bones by stimulating Hedgehog signaling."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
GPC6-null embryos display most of the abnormalities found in OMOD1
patients and that Hedgehog (Hh) signaling is significantly reduced in
the long bones of these embryos
explanation: >-
GPC6 knockout mice recapitulate OMOD1 phenotype and demonstrate that
reduced Hedgehog signaling in developing long bones is the key
pathogenic mechanism.
- reference: PMID:28696225
reference_title: "Glypican-6 promotes the growth of developing long bones by stimulating Hedgehog signaling."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
GPC6 stimulates Hh signaling by binding to Hh and Ptc1 at the cilium and
increasing the interaction of the receptor and ligand
explanation: >-
Establishes the molecular mechanism by which GPC6 promotes Hedgehog
signaling at the primary cilium.
- reference: PMID:28869591
reference_title: "Identification of 153 new loci associated with heel bone mineral density and functional involvement of GPC6 in osteoporosis."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The results implicate GPC6 as a novel determinant of BMD
explanation: >-
Large-scale GWAS identifies GPC6 as a determinant of bone mineral density
in the general population, supporting its broader role in skeletal
biology beyond omodysplasia.
downstream:
- target: Impaired chondrocyte proliferation and long bone growth
- name: FZD2 dysfunction and impaired Wnt signaling
description: >
In the dominant form, heterozygous nonsense mutations in FZD2 impair the
interaction of Frizzled-2 with Dishevelled, disrupting both canonical
(beta-catenin-dependent) and non-canonical (planar cell polarity) Wnt
signaling pathways in limb mesenchyme. This leads to shortened bone elements
through defective chondrocyte elongation and orientation.
cell_types:
- preferred_term: Growth plate chondrocyte
term:
id: CL:1000217
label: growth plate cartilage chondrocyte
biological_processes:
- preferred_term: Canonical Wnt signaling pathway
term:
id: GO:0060070
label: canonical Wnt signaling pathway
modifier: DECREASED
- preferred_term: Planar cell polarity pathway
term:
id: GO:0060071
label: Wnt signaling pathway, planar cell polarity pathway
modifier: DECREASED
- preferred_term: Endochondral ossification
term:
id: GO:0001958
label: endochondral ossification
modifier: DECREASED
gene:
preferred_term: FZD2
description: >-
Frizzled-2, a Wnt receptor that mediates both canonical and non-canonical
Wnt signaling pathways in limb development. Nonsense mutations impair
interaction with Dishevelled.
modifier: DECREASED
term:
id: hgnc:4040
label: FZD2
evidence:
- reference: PMID:25759469
reference_title: "A mutation in FRIZZLED2 impairs Wnt signaling and causes autosomal dominant omodysplasia."
supports: SUPPORT
evidence_source: IN_VITRO
snippet: >-
we show reduced ability of this mutant form of FZD2 to interact with its
downstream target DISHEVELLED. Furthermore, expressing the mutant form of
FZD2 in vitro is not able to facilitate the cellular response to canonical
Wnt signaling like wild-type FZD2
explanation: >-
Demonstrates that the FZD2 W548* mutation impairs Dishevelled interaction
and canonical Wnt signaling in functional assays.
- reference: PMID:36867021
reference_title: "FZD2 regulates limb development by mediating β-catenin-dependent and -independent Wnt signaling pathways."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
Fzd2em1Smill mutant embryos displayed decreased canonical Wnt signaling in
developing limb mesenchyme and disruption of digit chondrocyte elongation
and orientation, which is controlled by the β-catenin-independent
WNT5A/planar cell polarity (PCP) pathway
explanation: >-
Mouse model demonstrates that FZD2 mutations disrupt both canonical and
non-canonical Wnt signaling in limb development, directly causing
shortened bone elements.
- reference: PMID:36867021
reference_title: "FZD2 regulates limb development by mediating β-catenin-dependent and -independent Wnt signaling pathways."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
FZD2 controls limb development by mediating both canonical and
non-canonical Wnt pathways and reveal causality of pathogenic FZD2
mutations in RS and OMOD2 patients
explanation: >-
Confirms FZD2 as causative for OMOD2 and shows dual pathway involvement.
- reference: PMID:36967195
reference_title: "Non-canonical WNT5A-ROR signaling: New perspectives on an ancient developmental pathway."
supports: SUPPORT
evidence_source: OTHER
snippet: >-
mutations in each of these signaling components cause Robinow syndrome, a
congenital disorder characterized by profound tissue morphogenetic
abnormalities
explanation: >-
Review establishes that FZD2 is part of the core WNT5A-ROR-FZD-DVL
non-canonical signaling module, and that mutations in any component of
this pathway cause overlapping Robinow/omodysplasia phenotypes.
downstream:
- target: Impaired chondrocyte proliferation and long bone growth
- name: Impaired chondrocyte proliferation and long bone growth
description: >
The shared downstream consequence of both GPC6 and FZD2 deficiency is
impaired growth plate chondrocyte function. Growth plate cartilage shows
reduced chondrocyte proliferation and disorganized maturation, resulting in
defective endochondral ossification with shortened, malformed long bones.
cell_types:
- preferred_term: Growth plate chondrocyte
term:
id: CL:1000217
label: growth plate cartilage chondrocyte
biological_processes:
- preferred_term: Growth plate chondrocyte differentiation
term:
id: GO:0003418
label: growth plate cartilage chondrocyte differentiation
modifier: DECREASED
- preferred_term: Endochondral bone growth
term:
id: GO:0003416
label: endochondral bone growth
modifier: DECREASED
evidence:
- reference: PMID:19481194
reference_title: "Mutations in the heparan-sulfate proteoglycan glypican 6 (GPC6) impair endochondral ossification and cause recessive omodysplasia."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
Expression studies in microdissected mouse growth plate revealed expression
of Gpc6 in proliferative chondrocytes
explanation: >-
Demonstrates GPC6 expression in the relevant cell type (proliferative
growth plate chondrocytes), supporting the growth plate mechanism.
- reference: PMID:28696225
reference_title: "Glypican-6 promotes the growth of developing long bones by stimulating Hedgehog signaling."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
Hedgehog (Hh) signaling is significantly reduced in the long bones of
these embryos
explanation: >-
Reduced Hedgehog signaling in long bones of GPC6-null mice directly
explains the limb shortening phenotype.
- reference: PMID:9508243
reference_title: "Autosomal-recessive omodysplasia: prenatal diagnosis and histomorphometric assessment of the physeal plates of the long bones."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The pathological characteristics of the omodysplastic physeal plates were
an expanded zone of proliferating cartilage and an increased number of
closely packed, small chondrocytes
explanation: >-
Histomorphometric analysis of an omodysplastic fetus directly
demonstrates growth plate chondrocyte abnormalities, with compensatory
hyperplasia of small chondrocytes.
- reference: PMID:37353964
reference_title: "Five siblings expand the spectrum of GPC6-related skeletal dysplasia."
supports: SUPPORT
evidence_source: IN_VITRO
snippet: >-
the variant found in this family results in significantly reduced
stimulation of Hh activity when compared to the wild-type GPC6 protein,
however protein function is still present
explanation: >-
Hedgehog reporter assay demonstrates that GPC6 missense variant
p.Arg171Trp causes reduced but not abolished Hh signaling, explaining
the milder phenotype and confirming Hh as the key pathway.
phenotypes:
- category: Musculoskeletal
name: Rhizomelic limb shortening
description: >
Proximal limb shortening is a core manifestation. In GPC6-related disease,
both upper and lower limbs may be markedly involved, whereas FZD2-related
disease can show upper-limb-predominant rhizomelia.
phenotype_term:
preferred_term: Rhizomelic limb shortening
term:
id: HP:0008905
label: Rhizomelia
evidence:
- reference: PMID:14566439
reference_title: "Recessive omodysplasia: five new cases and review of the literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Clinical features are rhizomelic dwarfism with limited extension of elbows
and knees and a distinct face with a short nose, depressed nasal bridge,
long philtrum, midline haemangiomas in infants and cryptorchidism in males
explanation: >-
Supports rhizomelic limb shortening as a hallmark of recessive
omodysplasia.
- reference: PMID:29383834
reference_title: "Nonsense mutations in FZD2 cause autosomal-dominant omodysplasia: Robinow syndrome-like phenotypes."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The proband was a 16-year-old boy, who has been followed from infancy to
adolescence. He presented with rhizomelic short stature with elbow
restriction
explanation: >-
Confirms that rhizomelic shortening can also occur in FZD2-related
dominant omodysplasia.
phenotype_contexts:
- subtype: OMOD1
onset:
onset_category: ANTENATAL
notes: Second-semester ultrasonography documented short humeri and femora prenatally.
evidence:
- reference: PMID:9508243
reference_title: "Autosomal-recessive omodysplasia: prenatal diagnosis and histomorphometric assessment of the physeal plates of the long bones."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Second-semester ultrasonography of a female fetus documented short
femora and humeri and dislocation of the radii
explanation: >-
Demonstrates antenatal manifestation of proximal long-bone shortening in
recessive omodysplasia.
- category: Musculoskeletal
name: Short humerus
description: >
The humeri are short and often show distal tapering or relative
broadening/undermodeling on radiographs.
phenotype_term:
preferred_term: Short humerus
term:
id: HP:0005792
label: Short humerus
evidence:
- reference: PMID:2729357
reference_title: Omodysplasia.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Three cases of a new congenital bone disorder associating facial
anomalies (depressed nasal bridge, broad base of the nose, long philtrum)
with short humeri
explanation: >-
Original description of dominant omodysplasia identified short humeri as a
defining skeletal feature.
- reference: PMID:29383834
reference_title: "Nonsense mutations in FZD2 cause autosomal-dominant omodysplasia: Robinow syndrome-like phenotypes."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Radiological examination in infancy showed short, broad humeri with
relatively narrow distal ends
explanation: >-
Confirms shortened humeri with distal narrowing in molecularly confirmed
OMOD2.
- category: Musculoskeletal
name: Short femur
subtype: OMOD1
description: >
The femora are shortened in recessive omodysplasia and may show distal
tapering or undermodeling.
phenotype_term:
preferred_term: Short femur
term:
id: HP:0003097
label: Short femur
evidence:
- reference: PMID:9508243
reference_title: "Autosomal-recessive omodysplasia: prenatal diagnosis and histomorphometric assessment of the physeal plates of the long bones."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Second-semester ultrasonography of a female fetus documented short
femora and humeri and dislocation of the radii
explanation: >-
Provides direct evidence that femoral shortening is part of the recessive
phenotype and can be detected prenatally.
- reference: PMID:32655339
reference_title: "Novel Clinical and Radiological Findings in a Family with Autosomal Recessive Omodysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The pathognomonic radiological findings were distally tapered humeri and
femora as well as severe proximal radioulnar diastasis
explanation: >-
Confirms the characteristic tapered femoral morphology in molecularly
confirmed recessive omodysplasia.
- category: Musculoskeletal
name: Proximal radial head dislocation
description: >
Radial head dislocation is a characteristic elbow abnormality and is often
accompanied by proximal radioulnar diastasis.
phenotype_term:
preferred_term: Proximal radial head dislocation
term:
id: HP:0005070
label: Proximal radial head dislocation
evidence:
- reference: PMID:14566439
reference_title: "Recessive omodysplasia: five new cases and review of the literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Radiological findings are distal hypoplasia of the short humerus and femur
with characteristic radial dislocation and radioulnar diastasis
explanation: >-
Identifies radial head dislocation with radioulnar diastasis as a
characteristic radiologic feature of recessive omodysplasia.
- reference: PMID:25759469
reference_title: "A mutation in FRIZZLED2 impairs Wnt signaling and causes autosomal dominant omodysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Autosomal dominant omodysplasia is a rare skeletal dysplasia
characterized by short humeri, radial head dislocation, short first
metacarpals, facial dysmorphism and genitourinary anomalies
explanation: >-
Confirms that radial head dislocation is also part of the dominant
FZD2-related phenotype.
phenotype_contexts:
- subtype: OMOD1
onset:
onset_category: ANTENATAL
notes: Prenatal ultrasonography documented dislocation of the radii in a recessive case.
evidence:
- reference: PMID:9508243
reference_title: "Autosomal-recessive omodysplasia: prenatal diagnosis and histomorphometric assessment of the physeal plates of the long bones."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Second-semester ultrasonography of a female fetus documented short
femora and humeri and dislocation of the radii
explanation: >-
Shows antenatal detection of the forearm/elbow dislocation pattern in
recessive omodysplasia.
- category: Musculoskeletal
name: Limited elbow extension
description: >
Elbow motion is restricted, particularly extension, in both recessive and
dominant disease.
phenotype_term:
preferred_term: Limited elbow extension
term:
id: HP:0001377
label: Limited elbow extension
evidence:
- reference: PMID:14566439
reference_title: "Recessive omodysplasia: five new cases and review of the literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Clinical features are rhizomelic dwarfism with limited extension of elbows
and knees
explanation: >-
Supports elbow extension limitation in recessive omodysplasia.
- reference: PMID:29383834
reference_title: "Nonsense mutations in FZD2 cause autosomal-dominant omodysplasia: Robinow syndrome-like phenotypes."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
He presented with rhizomelic short stature with elbow restriction, mild
facial dysmorphism
explanation: >-
Confirms elbow restriction in a molecularly confirmed dominant case.
- category: Musculoskeletal
name: Limited knee extension
subtype: OMOD1
description: >
Knee extension can be limited in the recessive form alongside the elbow
contracture phenotype.
phenotype_term:
preferred_term: Limited knee extension
term:
id: HP:0003066
label: Limited knee extension
evidence:
- reference: PMID:14566439
reference_title: "Recessive omodysplasia: five new cases and review of the literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Clinical features are rhizomelic dwarfism with limited extension of elbows
and knees
explanation: >-
Directly supports limitation of knee extension in recessive omodysplasia.
- reference: PMID:32655339
reference_title: "Novel Clinical and Radiological Findings in a Family with Autosomal Recessive Omodysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Affected individuals manifest with rhizomelic short stature, decreased
mobility of elbow and knee joints as well as craniofacial anomalies
explanation: >-
Confirms recurrent knee-joint mobility limitation in molecularly
confirmed GPC6-related disease.
- category: Musculoskeletal
name: Short first metacarpal
subtype: OMOD2
description: >
Shortening of the first metacarpals is a characteristic hand finding in the
dominant form.
phenotype_term:
preferred_term: Short first metacarpal
term:
id: HP:0010034
label: Short 1st metacarpal
evidence:
- reference: PMID:25759469
reference_title: "A mutation in FRIZZLED2 impairs Wnt signaling and causes autosomal dominant omodysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Autosomal dominant omodysplasia is a rare skeletal dysplasia
characterized by short humeri, radial head dislocation, short first
metacarpals, facial dysmorphism and genitourinary anomalies
explanation: >-
Establishes short first metacarpals as part of the core dominant
phenotype.
- reference: PMID:29383834
reference_title: "Nonsense mutations in FZD2 cause autosomal-dominant omodysplasia: Robinow syndrome-like phenotypes."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Radiological examination in infancy showed short, broad humeri with
relatively narrow distal ends, mildly broad femora, thick proximal ulnae
with hypoplastic, dislocated proximal radii, and short first metacarpals
explanation: >-
Provides radiographic confirmation of first-metacarpal shortening in OMOD2.
- category: Musculoskeletal
name: Disproportionate short-limb short stature
subtype: OMOD1
description: >
Generalized short stature with disproportionate limb shortening is a major
feature of recessive omodysplasia; stature can be near normal in dominant
disease.
phenotype_term:
preferred_term: Disproportionate short-limb short stature
term:
id: HP:0008873
label: Disproportionate short-limb short stature
evidence:
- reference: PMID:19481194
reference_title: "Mutations in the heparan-sulfate proteoglycan glypican 6 (GPC6) impair endochondral ossification and cause recessive omodysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
autosomal-recessive omodysplasia, a genetic condition characterized by
short-limbed short stature, craniofacial dysmorphism, and variable
developmental delay
explanation: >-
Supports disproportionate short-limb short stature as a defining feature
of the recessive form.
- category: Craniofacial
name: Depressed nasal bridge
description: >
A depressed nasal bridge is part of the characteristic facial gestalt in
both recessive and dominant reports.
phenotype_term:
preferred_term: Depressed nasal bridge
term:
id: HP:0005280
label: Depressed nasal bridge
evidence:
- reference: PMID:14566439
reference_title: "Recessive omodysplasia: five new cases and review of the literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
a distinct face with a short nose, depressed nasal bridge, long philtrum
explanation: >-
Supports depressed nasal bridge in recessive omodysplasia.
- reference: PMID:2729357
reference_title: Omodysplasia.
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Three cases of a new congenital bone disorder associating facial
anomalies (depressed nasal bridge, broad base of the nose, long philtrum)
with short humeri
explanation: >-
Original dominant omodysplasia cases also showed a depressed nasal bridge.
- category: Craniofacial
name: Long philtrum
description: >
Long philtrum is part of the recurrent facial phenotype in both recessive
and dominant omodysplasia.
phenotype_term:
preferred_term: Long philtrum
term:
id: HP:0000343
label: Long philtrum
evidence:
- reference: PMID:14566439
reference_title: "Recessive omodysplasia: five new cases and review of the literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
a distinct face with a short nose, depressed nasal bridge, long philtrum
explanation: >-
Supports long philtrum in recessive omodysplasia.
- reference: PMID:29383834
reference_title: "Nonsense mutations in FZD2 cause autosomal-dominant omodysplasia: Robinow syndrome-like phenotypes."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
craniofacial dysmorphism (frontal bossing, depressed nasal bridge, bifid
nasal tip, and long philtrum)
explanation: >-
Confirms that long philtrum is also part of the dominant OMOD2 facial
phenotype.
- category: Craniofacial
name: Frontal bossing
subtype: OMOD2
description: >
Frontal bossing is part of the Robinow-like craniofacial phenotype reported
in dominant omodysplasia.
phenotype_term:
preferred_term: Frontal bossing
term:
id: HP:0002007
label: Frontal bossing
evidence:
- reference: PMID:29383834
reference_title: "Nonsense mutations in FZD2 cause autosomal-dominant omodysplasia: Robinow syndrome-like phenotypes."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
craniofacial dysmorphism (frontal bossing, depressed nasal bridge, bifid
nasal tip, and long philtrum)
explanation: >-
Frontal bossing is listed among the defining craniofacial features of OMOD2.
- category: Craniofacial
name: Short nose
description: >
Short nose is part of the characteristic facial appearance in both forms,
although the accompanying nasal configuration differs across reports.
phenotype_term:
preferred_term: Short nose
term:
id: HP:0003196
label: Short nose
evidence:
- reference: PMID:14566439
reference_title: "Recessive omodysplasia: five new cases and review of the literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
a distinct face with a short nose, depressed nasal bridge, long philtrum
explanation: >-
Supports short nose in recessive omodysplasia.
- reference: PMID:29383834
reference_title: "Nonsense mutations in FZD2 cause autosomal-dominant omodysplasia: Robinow syndrome-like phenotypes."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
He presented with rhizomelic short stature with elbow restriction, mild
facial dysmorphism (depressed broad bridge, short nose, anteverted
nostrils, long philtrum, and low-set ears), and genital hypoplasia
explanation: >-
Confirms short nose in a molecularly confirmed dominant case.
- category: Craniofacial
name: Anteverted nares
subtype: OMOD2
description: >
Anteverted nares are part of the reported dominant craniofacial phenotype.
phenotype_term:
preferred_term: Anteverted nares
term:
id: HP:0000463
label: Anteverted nares
evidence:
- reference: PMID:29383834
reference_title: "Nonsense mutations in FZD2 cause autosomal-dominant omodysplasia: Robinow syndrome-like phenotypes."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
He presented with rhizomelic short stature with elbow restriction, mild
facial dysmorphism (depressed broad bridge, short nose, anteverted
nostrils, long philtrum, and low-set ears), and genital hypoplasia
explanation: >-
Directly supports anteverted nares in FZD2-related dominant omodysplasia.
- category: Craniofacial
name: Bifid nasal tip
subtype: OMOD2
description: >
Bifid nasal tip has been reported as part of the OMOD2 facial phenotype.
phenotype_term:
preferred_term: Bifid nasal tip
term:
id: HP:0000456
label: Bifid nasal tip
evidence:
- reference: PMID:29383834
reference_title: "Nonsense mutations in FZD2 cause autosomal-dominant omodysplasia: Robinow syndrome-like phenotypes."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
craniofacial dysmorphism (frontal bossing, depressed nasal bridge, bifid
nasal tip, and long philtrum)
explanation: >-
Directly supports bifid nasal tip in dominant omodysplasia.
- category: Craniofacial
name: Low-set ears
subtype: OMOD2
description: >
Low-set ears were described in a molecularly confirmed dominant case.
phenotype_term:
preferred_term: Low-set ears
term:
id: HP:0000369
label: Low-set ears
evidence:
- reference: PMID:29383834
reference_title: "Nonsense mutations in FZD2 cause autosomal-dominant omodysplasia: Robinow syndrome-like phenotypes."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
He presented with rhizomelic short stature with elbow restriction, mild
facial dysmorphism (depressed broad bridge, short nose, anteverted
nostrils, long philtrum, and low-set ears), and genital hypoplasia
explanation: >-
Supports low-set ears as part of the OMOD2 facial phenotype.
- category: Craniofacial
name: Cleft lip
subtype: OMOD2
description: >
Orofacial clefting with cleft lip has been reported in a subset of
molecularly confirmed FZD2-related cases.
phenotype_term:
preferred_term: Cleft lip
term:
id: HP:0410030
label: Cleft lip
evidence:
- reference: PMID:29230162
reference_title: "A Novel de novo FZD2 Mutation in a Patient with Autosomal Dominant Omodysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
We described a heterozygous de novo mutation (G434V) in the frizzled
class receptor 2 (FZD2) gene in a patient with distinct facial features
including hypertelorism, bilateral cleft lip/palate, short nose with a
broad nasal bridge, microretrognathia
explanation: >-
Documents cleft lip in a molecularly confirmed dominant case.
- reference: PMID:41022130
reference_title: "[Omodysplasia Type II - first publication of de novo Mutation in FZD2 Gene]."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
We describe a prenatally detected case with shortened upper extremities,
cleft lip and palate and suspected genital hypoplasia
explanation: >-
Additional recent prenatal case confirms that cleft lip can be part of
the OMOD2 spectrum.
- category: Craniofacial
name: Cleft palate
subtype: OMOD2
description: >
Cleft palate has been reported with FZD2-related dominant omodysplasia,
usually alongside cleft lip.
phenotype_term:
preferred_term: Cleft palate
term:
id: HP:0000175
label: Cleft palate
evidence:
- reference: PMID:29230162
reference_title: "A Novel de novo FZD2 Mutation in a Patient with Autosomal Dominant Omodysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
We described a heterozygous de novo mutation (G434V) in the frizzled
class receptor 2 (FZD2) gene in a patient with distinct facial features
including hypertelorism, bilateral cleft lip/palate, short nose with a
broad nasal bridge, microretrognathia
explanation: >-
Documents cleft palate in a molecularly confirmed dominant case.
- reference: PMID:41022130
reference_title: "[Omodysplasia Type II - first publication of de novo Mutation in FZD2 Gene]."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
We describe a prenatally detected case with shortened upper extremities,
cleft lip and palate and suspected genital hypoplasia
explanation: >-
Additional recent prenatal case confirms that cleft palate can be part of
the OMOD2 spectrum.
- category: Dermatological
name: Facial midline hemangioma
subtype: OMOD1
description: >
Midline facial hemangiomas in infancy are reported in the recessive form.
phenotype_term:
preferred_term: Facial midline hemangioma
term:
id: HP:0007601
label: Midline facial capillary hemangioma
evidence:
- reference: PMID:14566439
reference_title: "Recessive omodysplasia: five new cases and review of the literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
midline haemangiomas in infants
explanation: >-
Midline hemangiomas in infancy are described as a feature of the
recessive form.
- category: Genitourinary
name: Cryptorchidism
subtype: OMOD1
description: >
Cryptorchidism in males is a recurrent feature in the recessive form.
phenotype_term:
preferred_term: Cryptorchidism
term:
id: HP:0000028
label: Cryptorchidism
evidence:
- reference: PMID:14566439
reference_title: "Recessive omodysplasia: five new cases and review of the literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
cryptorchidism in males
explanation: >-
Cryptorchidism is described as a feature in males with the recessive form.
- category: Genitourinary
name: External genital hypoplasia
subtype: OMOD2
description: >
Hypoplastic male external genitalia are part of the dominant phenotype;
ambiguous genitalia was reported in one affected boy.
phenotype_term:
preferred_term: External genital hypoplasia
term:
id: HP:0003241
label: External genital hypoplasia
evidence:
- reference: PMID:29383834
reference_title: "Nonsense mutations in FZD2 cause autosomal-dominant omodysplasia: Robinow syndrome-like phenotypes."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
rhizomelic short stature with elbow restriction, mild facial dysmorphism
(depressed broad bridge, short nose, anteverted nostrils, long philtrum,
and low-set ears), and genital hypoplasia
explanation: >-
Supports genital hypoplasia in a molecularly confirmed dominant case.
- reference: PMID:12210345
reference_title: "Omodysplasia: an affected mother and son."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Her son had ambiguous genitalia and similar skeletal manifestations as
his mother. A comparison to other known and suspected cases of dominant
omodysplasia is presented. Our observations confirm the existence of a
dominant variant of omodysplasia, document genital hypoplasia as an
important feature of this syndrome in males
explanation: >-
Independent dominant family confirms that male genital hypoplasia is an
important feature and can present as ambiguous genitalia.
- category: Cardiovascular
name: Congenital heart defect
subtype: OMOD1
description: >
Congenital heart defects have been reported in recessive omodysplasia, but
current evidence supports them as an uncommon associated finding rather than
a core diagnostic feature.
phenotype_term:
preferred_term: Congenital heart defect
term:
id: HP:0001627
label: Abnormal heart morphology
evidence:
- reference: PMID:8209882
reference_title: "Parental consanguinity in two sibs with omodysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Two sibs with omodysplasia were born to phenotypically normal but
consanguineous parents. They had severe micromelic dwarfism, facial
anomalies, and mental retardation. One had a congenital heart defect
explanation: >-
Documents congenital heart defect in a molecularly confirmed recessive
family, supporting inclusion as an associated but apparently uncommon
extraskeletal manifestation.
- category: Neurological
name: Global developmental delay
subtype: OMOD1
description: >
Neurodevelopmental delay has been reported variably in recessive
omodysplasia; current evidence does not support treating intellectual
disability as a consistent dominant-feature claim.
phenotype_term:
preferred_term: Global developmental delay
term:
id: HP:0001263
label: Global developmental delay
evidence:
- reference: PMID:19481194
reference_title: "Mutations in the heparan-sulfate proteoglycan glypican 6 (GPC6) impair endochondral ossification and cause recessive omodysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
short-limbed short stature, craniofacial dysmorphism, and variable
developmental delay
explanation: >-
Supports variable developmental delay in GPC6-related recessive
omodysplasia.
genetic:
- name: GPC6 mutations
subtype: OMOD1
gene_term:
preferred_term: GPC6
term:
id: hgnc:4454
label: GPC6
inheritance:
- name: Autosomal recessive
inheritance_term:
preferred_term: Autosomal recessive inheritance
term:
id: HP:0000007
label: Autosomal recessive inheritance
features: >-
Biallelic loss-of-function mutations including nonsense mutations, splice site
mutations, and larger genomic rearrangements such as exon deletions. Most
identified mutations truncate the GPC6 protein. Hypomorphic missense variants
(e.g. p.Arg171Trp) have been reported with a milder phenotype, expanding the
genotype-phenotype spectrum.
evidence:
- reference: PMID:19481194
reference_title: "Mutations in the heparan-sulfate proteoglycan glypican 6 (GPC6) impair endochondral ossification and cause recessive omodysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
autosomal-recessive omodysplasia, a genetic condition characterized by
short-limbed short stature, craniofacial dysmorphism, and variable
developmental delay, maps to chromosome 13 (13q31.1-q32.2) and is caused
by point mutations or by larger genomic rearrangements in glypican 6 (GPC6)
explanation: >-
Maps the disease locus and identifies the causative gene with the
spectrum of mutation types.
- reference: PMID:32655339
reference_title: "Novel Clinical and Radiological Findings in a Family with Autosomal Recessive Omodysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
A homozygous deletion of exon 6 in the GPC6 gene was detected
explanation: >-
Confirms that larger genomic rearrangements (exon deletions) in GPC6
also cause the recessive form.
- reference: PMID:37353964
reference_title: "Five siblings expand the spectrum of GPC6-related skeletal dysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
All affected individuals were found to have homozygous missense variants
in GPC6: c.511 C>T (p.Arg171Trp)
explanation: >-
Identifies a hypomorphic GPC6 missense variant causing a milder skeletal
dysplasia phenotype, expanding the mutation spectrum beyond truncating
mutations.
- name: FZD2 mutations
subtype: OMOD2
gene_term:
preferred_term: FZD2
term:
id: hgnc:4040
label: FZD2
inheritance:
- name: Autosomal dominant
inheritance_term:
preferred_term: Autosomal dominant inheritance
term:
id: HP:0000006
label: Autosomal dominant inheritance
features: >-
Heterozygous mutations in FZD2 including nonsense mutations in the C-terminal
Dishevelled-interacting domain (p.Trp548*, p.Ser547*) and missense mutations
(p.Gly434Val) affecting protein function. Most cases are de novo.
evidence:
- reference: PMID:25759469
reference_title: "A mutation in FRIZZLED2 impairs Wnt signaling and causes autosomal dominant omodysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The FZD2 mutation (c.1644G>A) changes a tryptophan residue at amino acid
548 to a premature stop (p.Trp548*)
explanation: >-
First identification of the p.Trp548* nonsense mutation in FZD2 as the
cause of autosomal dominant omodysplasia.
- reference: PMID:29383834
reference_title: "Nonsense mutations in FZD2 cause autosomal-dominant omodysplasia: Robinow syndrome-like phenotypes."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Molecular analysis identified a de novo, heterozygous, nonsense mutation
(c.1640C>A, p.S547*) in FZD2. The affected codon was next to the
previously reported mutation (p.Trp548*)
explanation: >-
Second FZD2 nonsense mutation at an adjacent codon confirms a mutational
hotspot in the C-terminal Dishevelled-interacting domain.
- reference: PMID:30455931
reference_title: "Two unrelated patients with autosomal dominant omodysplasia and FRIZZLED2 mutations."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
two patients with autosomal dominant omodysplasia and mutations in the
FZD2 gene. The mutations identified have been recently reported,
suggesting the possibility of recurrent mutations
explanation: >-
Additional unrelated patients with FZD2 mutations support recurrence at
the same hotspot.
- reference: PMID:29230162
reference_title: "A Novel de novo FZD2 Mutation in a Patient with Autosomal Dominant Omodysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
a heterozygous de novo mutation (G434V) in the frizzled class receptor 2
(FZD2) gene in a patient with distinct facial features including
hypertelorism, bilateral cleft lip/palate, short nose with a broad nasal
bridge, microretrognathia, and bilateral shortness of the upper limbs
explanation: >-
Identifies a missense FZD2 mutation (G434V) distinct from the C-terminal
nonsense hotspot, expanding the mutation spectrum to include missense
variants and broadening the phenotypic range to include cleft lip/palate.
animal_models:
- species: Mouse
genotype: Gpc6 knockout
description: >
GPC6-null mice recapitulate the skeletal phenotype of autosomal recessive
omodysplasia, with shortened long bones and significantly reduced Hedgehog
signaling in developing long bones.
genes:
- preferred_term: GPC6
term:
id: hgnc:4454
label: GPC6
associated_phenotypes:
- Short limbs
- Reduced Hedgehog signaling in long bones
evidence:
- reference: PMID:28696225
reference_title: "Glypican-6 promotes the growth of developing long bones by stimulating Hedgehog signaling."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
GPC6-null embryos display most of the abnormalities found in OMOD1
patients and that Hedgehog (Hh) signaling is significantly reduced in
the long bones of these embryos
explanation: >-
GPC6 knockout mouse validates the loss-of-function mechanism and
directly models the human recessive phenotype.
- species: Mouse
genotype: Fzd2em1Smill (single-nucleotide insertion causing frameshift)
description: >
Fzd2 mutant mice harboring a frameshift mutation in the final
Dishevelled-interacting domain develop shortened limbs resembling human
dominant omodysplasia and Robinow syndrome, with decreased canonical Wnt
signaling in limb mesenchyme and disrupted chondrocyte polarity.
genes:
- preferred_term: FZD2
term:
id: hgnc:4040
label: FZD2
associated_phenotypes:
- Short limbs
- Decreased canonical Wnt signaling in limb mesenchyme
- Disrupted chondrocyte elongation and orientation
evidence:
- reference: PMID:36867021
reference_title: "FZD2 regulates limb development by mediating β-catenin-dependent and -independent Wnt signaling pathways."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: >-
Fzd2em1Smill mutant mice had shortened limbs, resembling those of RS and
OMOD2 patients, indicating that FZD2 mutations are causative
explanation: >-
Fzd2 frameshift mouse model recapitulates the shortened limb phenotype
of dominant omodysplasia, confirming causality.
prevalence:
- population: Global
percentage: Unknown
notes: >-
Omodysplasia is extremely rare. Fewer than 20 cases of the recessive form
had been reported by 2004, and approximately 10 cases of the dominant form
had been reported by 2022.
evidence:
- reference: PMID:14566439
reference_title: "Recessive omodysplasia: five new cases and review of the literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Fewer than 20 cases have been reported in the literature so far
explanation: >-
Establishes the extreme rarity of the recessive form with fewer than
20 published cases as of 2004.
- reference: PMID:35937024
reference_title: "Dominant omodysplasia-A sporadic case-A new case report and review of the literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
ten cases of the autosomal dominant type of this disease have been
reported
explanation: >-
Documents the rarity of the dominant form with approximately 10 reported
cases as of 2022.
diagnosis:
- name: Clinical, Radiographic, and Molecular Diagnosis
description: >-
Omodysplasia is diagnosed from short-limbed short stature with severe
proximal (rhizomelic) limb shortening, characteristic facial dysmorphism,
and radiographic findings, and is subtyped by molecular genetic testing:
autosomal recessive omodysplasia from biallelic GPC6 variants and
autosomal dominant omodysplasia from heterozygous FZD2 variants.
diagnosis_term:
preferred_term: molecular genetic testing
term:
id: MAXO:0000533
label: molecular genetic testing
evidence:
- reference: PMID:19481194
reference_title: "Mutations in the heparan-sulfate proteoglycan glypican 6 (GPC6) impair endochondral ossification and cause recessive omodysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "autosomal-recessive omodysplasia, a genetic condition characterized by short-limbed short stature, craniofacial dysmorphism, and variable developmental delay, maps to chromosome 13 (13q31.1-q32.2) and is caused by point mutations or by larger genomic rearrangements in glypican 6 (GPC6)"
explanation: >-
Defines the clinical features and GPC6 molecular basis of autosomal recessive omodysplasia.
- reference: PMID:25759469
reference_title: "A mutation in FRIZZLED2 impairs Wnt signaling and causes autosomal dominant omodysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "We identified a de novo mutation in FRIZZLED2 (FZD2) in the proband and her daughter that was not found in unaffected family members"
explanation: >-
Supports FZD2 molecular testing for the autosomal dominant form of omodysplasia.
progression:
- subtype: OMOD1
notes: >-
Skeletal changes in recessive omodysplasia are regressive with age. The
humerofemoral abnormalities, including distal tapering and club-like
morphology, improve over time, and the growth plate compensatory
hyperplasia of chondrocytes suggests partial adaptive mechanisms.
evidence:
- reference: PMID:14566439
reference_title: "Recessive omodysplasia: five new cases and review of the literature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
the regressive nature of the humerofemoral changes
explanation: >-
Clinical review documents that the characteristic long bone abnormalities
improve with age in recessive omodysplasia.
- reference: PMID:9508243
reference_title: "Autosomal-recessive omodysplasia: prenatal diagnosis and histomorphometric assessment of the physeal plates of the long bones."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
a genetic, functional deficiency of the physeal cells, underlying the
short-limbed dwarfism of autosomal-recessive omodysplasia, is partially
compensated, albeit ineffectively, by an increased number of small
chondrocytes in the proliferating zone of the physeal plate
explanation: >-
Histomorphometric evidence of a compensatory mechanism in the growth plate,
with increased chondrocyte numbers partially offsetting the functional
deficiency.
- subtype: OMOD2
notes: >-
In dominant omodysplasia, the skeletal phenotype is persistent into
adulthood. Long-term observation shows humeri and femora become less
undermodeled with age, but may develop mild bowing. Mild lower extremity
rhizomelia may become apparent over time.
evidence:
- reference: PMID:29383834
reference_title: "Nonsense mutations in FZD2 cause autosomal-dominant omodysplasia: Robinow syndrome-like phenotypes."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
The abnormal skeletal pattern was persistent in adolescence; however, the
humeri and femora became less undermodeled, while the humeri and radii
became mildly bowed
explanation: >-
Long-term radiological follow-up from infancy to adolescence documents
persistence but evolution of the skeletal phenotype.
- reference: PMID:24458798
reference_title: "Long-term observation of a patient with dominant omodysplasia."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: >-
Mild rhizomelic shortening of the lower extremities has not been
previously reported
explanation: >-
Long-term follow-up reveals mild lower extremity involvement in dominant
omodysplasia that was not apparent in earlier descriptions.
treatments:
- name: Orthopedic surgical management
description: >
Surgical intervention for management of radial head dislocation and other
skeletal deformities. Limb-lengthening procedures may be considered in severe
cases.
treatment_term:
preferred_term: Orthopedic surgical management
term:
id: MAXO:0000004
label: surgical procedure
- name: Physical therapy
description: >
Rehabilitation to maintain and improve joint range of motion, particularly
at the elbows and knees where restricted extension is common.
treatment_term:
preferred_term: Physical therapy
term:
id: MAXO:0000011
label: physical therapy
- name: Genetic counseling
description: >
Genetic counseling for families, particularly to distinguish between the
autosomal recessive and autosomal dominant forms and to inform recurrence
risk assessment.
treatment_term:
preferred_term: Genetic counseling
term:
id: MAXO:0000079
label: genetic counseling
notes: >
The nosological distinction between autosomal recessive and autosomal dominant
omodysplasia reflects different genetic etiologies (GPC6 vs FZD2) converging on
related signaling pathways (Hedgehog vs Wnt) that regulate endochondral
ossification. The phenotypic overlap with autosomal dominant Robinow syndrome
(also caused by WNT pathway mutations) raises questions about whether OMOD2
and AD Robinow syndrome represent a clinical continuum. Congenital heart
defects (atrial septal defect, patent ductus arteriosus) have been reported in
a minority of OMOD1 cases in the literature, but this is not consistently
documented in available abstracts and requires further primary source
verification.
This report is retrieval-only and is generated directly from Asta results.
search_papers_by_relevance with snippet_search.Disease Name: Omodysplasia (OMOD) – a rare genetic skeletal dysplasia affecting limb development
MONDO ID: MONDO:0009779 (Autosomal recessive form, OMOD1); MONDO:0008123 (Autosomal dominant form, OMOD2)
Category: Mendelian disorder (skeletal dysplasia)
Omodysplasia is characterized by profound disruptions in endochondral bone development driven by mutations in key developmental signaling pathways. In autosomal recessive Omodysplasia (OMOD1), biallelic loss-of-function mutations in GPC6 (glypican 6) impair Hedgehog signaling in growth plate cartilage (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Glypican-6 is a cell-surface heparan sulfate proteoglycan that normally augments Indian hedgehog (IHH) signaling during bone growth. Loss of GPC6 results in reduced Hedgehog pathway activity in the cartilage growth plate, leading to defective chondrocyte proliferation and impaired endochondral ossification (GO:0001958) (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Consequently, long bones cannot elongate normally, causing rhizomelic (proximal) limb shortening and skeletal deformities. In the autosomal dominant form (OMOD2), heterozygous mutations in FZD2 (Frizzled-2) disrupt Wnt signaling required for limb and facial morphogenesis (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Frizzled-2 is a receptor for Wnt morphogens, and pathogenic truncating mutations (e.g. p.Trp548) abolish the receptor’s intracellular Dishevelled-binding motif (pmc.ncbi.nlm.nih.gov). The mutant FZD2 cannot effectively transmit canonical Wnt signals (GO:0060070), leading to significantly blunted Wnt/β-catenin pathway activity in osteochondral cells (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). This Wnt signal failure impairs limb bud development and growth plate function, particularly affecting the formation of the humerus and radius (www.ncbi.nlm.nih.gov). In summary, Omodysplasia’s core pathology is a developmental signaling failure* – Hedgehog pathway insufficiency (in OMOD1) and Wnt pathway perturbation (in OMOD2) – that converges on abnormal cartilage template formation and ossification. These molecular derangements translate into stunted bone growth, skeletal patterning defects, and the characteristic clinical dwarfism and dysmorphology.
Genes/Proteins: The two genes causally implicated in Omodysplasia are GPC6 (HGNC:4454) and FZD2 (HGNC:4040). GPC6 encodes glypican-6, a glycosylphosphatidylinositol (GPI)-anchored heparan sulfate proteoglycan on the cell surface (pmc.ncbi.nlm.nih.gov). Glypican-6 acts as a co-receptor for morphogens; notably, it binds Hedgehog ligands and the Patched-1 (PTCH1) receptor to facilitate Hedgehog signal transduction in chondrocytes (pmc.ncbi.nlm.nih.gov). “GPC6 seems to have a previously unsuspected role in endochondral ossification and skeletal growth, and its functional abrogation results in a short-limb phenotype” (pmc.ncbi.nlm.nih.gov), as discovered by Campos-Xavier et al. (2009). All known disease-causing GPC6 mutations (e.g. nonsense and frameshift variants) produce truncated proteins lacking the GPI-anchor and heparan sulfate attachment sites, resulting in complete loss of glypican-6 function (pmc.ncbi.nlm.nih.gov). This abolishes GPC6’s ability to stimulate Hedgehog signaling, which is crucial for normal cartilage maturation (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). The FZD2 gene encodes Frizzled-2, a 7-transmembrane Wnt receptor. Frizzled-2 is broadly expressed during embryonic limb and craniofacial development (pmc.ncbi.nlm.nih.gov), where it transduces Wnt signals required for tissue patterning. Pathogenic FZD2 mutations in OMOD2 are typically truncating (e.g. a C-terminal nonsense mutation p.Trp548 identified by Saal et al., 2015 (pmc.ncbi.nlm.nih.gov)). The mutant Frizzled-2 protein is produced but lacks part of the cytoplasmic tail, including the conserved KTXXXW motif needed to recruit Dishevelled (DVL) upon Wnt binding (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). As a result, the truncated FZD2 cannot effectively initiate the canonical Wnt/β-catenin cascade. In functional assays, the truncated FZD2 was “significantly less efficient in transducing WNT signaling than the wild-type FZD2” (pmc.ncbi.nlm.nih.gov), leading to haploinsufficiency or a dominant-negative effect in Wnt-dependent developmental processes (pmc.ncbi.nlm.nih.gov). In addition to these primary genes, downstream signaling proteins are involved: for OMOD1, the Hedgehog pathway components such as the ligand Indian hedgehog (IHH) and its receptors PTCH1 and SMO (Smoothened) are relevant – GPC6 normally enhances their interaction (pmc.ncbi.nlm.nih.gov). For OMOD2, Wnt ligands (e.g. WNT5A and others expressed in limb mesenchyme) and intracellular effectors DVL2, β-catenin, and TCF/LEF* transcription factors play roles in the disrupted pathway (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Notably, WNT5A and its receptor ROR2 are linked to Robinow syndrome (a disorder with overlapping limb/facial phenotypes), highlighting that FZD2 mutations likely perturb similar developmental signaling routes (pmc.ncbi.nlm.nih.gov).
Chemical Entities: A key molecular entity in OMOD1 pathology is heparan sulfate (HS) – the glycosaminoglycan side chain of glypican-6. Heparan sulfate (CHEBI:28815) attached to GPC6 is essential for binding morphogens. GPC6’s HS chains physically interact with Hedgehog proteins and with PTCH1 (pmc.ncbi.nlm.nih.gov), effectively tethering the ligand-receptor complex. In GPC6 deficiency, this extracellular matrix factor is lacking, so Hedgehog ligands cannot form proper gradients or signaling complexes (pmc.ncbi.nlm.nih.gov). No specific exogenous small-molecule toxins or metabolites are known to cause Omodysplasia; it is a purely genetic disorder. However, the pathways involved have chemical modulators: for example, Wnt signaling inhibitors or Hedgehog pathway agonists are of theoretical interest. (To date, no drug therapy exists for Omodysplasia, but understanding that glypican-6 binds Hedgehog suggests that Hedgehog agonists might partially compensate, as observed in research models (pubmed.ncbi.nlm.nih.gov).) Overall, the relevant “chemical” players are the endogenous morphogen ligands (Hedgehog, Wnt) and the heparan sulfate matrix components facilitating their signaling.
Cell Types: The primary cell type affected in Omodysplasia is the chondrocyte (CL:0000138), specifically growth plate chondrocytes in developing long bones. GPC6 is normally expressed in proliferative zone chondrocytes of the growth plate (pmc.ncbi.nlm.nih.gov), which are the cartilage cells responsible for longitudinal bone growth. In GPC6-related OMOD1, these chondrocytes show markedly reduced signaling activity and impaired proliferation (pmc.ncbi.nlm.nih.gov). This leads to fewer chondrocytes maturing and hypertrophying, thus stunting bone elongation. Hypertrophic chondrocytes and osteoblasts (CL:0000062) are also indirectly affected, since Hedgehog signaling from prehypertrophic chondrocytes normally regulates their differentiation. In FZD2-related OMOD2, the affected cells include mesenchymal cells of the limb buds and osteochondral progenitors that rely on Wnt signals for proper patterning. Craniofacial osteoblasts and chondrocranial cells are similarly impacted by the disrupted Wnt signaling, explaining the facial dysmorphisms (www.ncbi.nlm.nih.gov). Notably, other cell types in organs that sometimes show anomalies (heart, genitalia) could be involved: for instance, cardiac valve mesenchyme and gonadal cells might be subtly affected due to the widespread roles of Wnt/Hedgehog in development (supporting the variable heart defects and cryptorchidism in some cases (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov)). Nonetheless, the disease pathology primarily centers on chondrocytes of the growth plate and their osteogenic counterparts.
Anatomical Locations: Omodysplasia chiefly involves the appendicular skeleton (UBERON:0002384), especially the proximal long bones of the arms and legs. The term “Omodysplasia” comes from Greek omos (shoulder), reflecting the prominent shortening of the humerus (UBERON:0002269) (pmc.ncbi.nlm.nih.gov). In autosomal dominant OMOD2, the upper limbs are most affected, with short humeri and elbow abnormalities (e.g., dislocated radial head of the radius bone (UBERON:0001306)) (www.ncbi.nlm.nih.gov). Autosomal recessive OMOD1 involves both upper and lower limbs: the humeri and femora (UBERON:0002445) are shortened and show metaphyseal flaring and distal tapering (narrowing towards the ends) (pmc.ncbi.nlm.nih.gov). The proximal radioulnar joint can be malformed (diastasis and radial head dislocation) leading to limited elbow extension (pubmed.ncbi.nlm.nih.gov). The knees may also be stiff due to abnormal distal femur and proximal tibia development (pmc.ncbi.nlm.nih.gov). The hands sometimes show shortened first metacarpals (UBERON:0001427), particularly in OMOD2 (www.ncbi.nlm.nih.gov). Craniofacial structures are another anatomical focus: patients have characteristic facial dysmorphology involving the skull and midface (UBERON:0001707) – including frontal bone prominence, nasal bridge, philtrum, etc. (see Phenotypes below). Additionally, some internal organs can be involved: for example, a subset of cases have congenital heart defects (e.g., atrial septal defect, patent ductus arteriosus) (pmc.ncbi.nlm.nih.gov), suggesting involvement of cardiac outflow tract structures (UBERON:0004174) during embryogenesis. Some males have cryptorchidism (undescended testes), implicating development of the inguinal canal/gubernaculum (UBERON:0036278). These systemic involvements are less consistent but highlight that the mutations affect developmental processes across multiple anatomical sites. Importantly, the epiphyseal growth plates (UBERON:0002495) of long bones are the central anatomical locations where the molecular pathology plays out, resulting in the limb deformities that define Omodysplasia (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov).
Several biological processes are disrupted in Omodysplasia, reflecting the roles of GPC6 and FZD2 in development:
Hedgehog signaling pathway (GO:0007224): The Hedgehog (Hh) signaling cascade is significantly downregulated in GPC6-related OMOD1. Normally, IHH produced by growth plate chondrocytes signals via PTCH1/SMO on neighboring cells to promote chondrocyte proliferation and prevent premature hypertrophy. Glypican-6 is required to efficiently present Hedgehog ligand to its receptor at the cell surface (pmc.ncbi.nlm.nih.gov). In GPC6-deficient chondrocytes, Hedgehog pathway activity is “significantly reduced in the long bones” (pmc.ncbi.nlm.nih.gov), leading to a failure of proper growth plate signaling. This is evidenced by GPC6-null mouse embryos, which show curtailed Hh signaling and recapitulate the Omodysplasia skeletal phenotype (pmc.ncbi.nlm.nih.gov). Thus, the normal biological process of Hedgehog-mediated signal transduction in bone development is impaired, causing truncated bone growth.
Wnt signaling pathway (canonical) (GO:0060070): Wnt/β-catenin signaling is perturbed in FZD2-related OMOD2. Canonical Wnt signaling in osteoblast and chondrocyte precursors drives cell proliferation and skeletal patterning during limb and craniofacial development. The Frizzled-2 receptor normally binds Wnt ligands and, via Dishevelled, stabilizes β-catenin for gene transcription. In OMOD2, the mutated Frizzled-2 cannot propagate the Wnt signal, leading to markedly diminished pathway output (pmc.ncbi.nlm.nih.gov). Saal et al. (2015) showed that cells expressing the mutant FZD2 failed to activate a Wnt-responsive luciferase reporter (TOPFLASH assay), whereas wild-type FZD2 yielded ~3-fold induction (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). The authors conclude the patients’ cells are effectively haploinsufficient for Wnt signaling during skeletal development (pmc.ncbi.nlm.nih.gov). Therefore, the biological process of canonical Wnt signal transduction is disrupted in Omodysplasia, contributing to abnormal limb formation and bone growth.
Endochondral ossification (GO:0001958): This is the process by which cartilage is gradually replaced by bone in the developing skeleton. Endochondral ossification is fundamentally impaired in Omodysplasia (pmc.ncbi.nlm.nih.gov). Due to Hedgehog and Wnt signaling defects, the coordination between chondrocyte maturation and osteoblast activity is lost. Normally, proliferating chondrocytes lay down a cartilage template, then undergo hypertrophy and apoptosis, while osteoprogenitors invade to form bone tissue. In GPC6-deficient individuals, endochondral bone formation is delayed and disorganized (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Growth plates show reduced chondrocyte proliferation and possibly altered hypertrophic zones, leading to shortened metaphyses. Campos-Xavier et al. noted that loss of GPC6 abrogates a critical function in endochondral ossification, resulting in the short-limb dwarfism phenotype (pmc.ncbi.nlm.nih.gov). Thus, the entire sequence of events in endochondral bone growth is disrupted – a central pathophysiological mechanism in Omodysplasia.
Cartilage development and morphogenesis (GO:0051216, GO:0060350): Related to ossification, the early developmental processes of cartilage patterning in the limb are also affected. GPC6 and FZD2 mutations alter the behavior of limb bud mesenchymal cells that condense into cartilage models of bones. Aberrant Hedgehog/Wnt signaling likely disturbs chondrocyte differentiation (GO:0035988) and cartilage morphogenesis. For example, the organization of growth plate cartilage is abnormal in GPC6-null mice, who display shortened long bone cartilage templates and delayed ossification centers (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Similarly, FZD2-related Wnt deficits can affect cell fate specification in limb mesenchyme (a Wnt-driven process), leading to defects like missing or shortened bone segments (e.g. first metacarpal shortening in OMOD2 (www.ncbi.nlm.nih.gov)). Although specific gene ontology terms cover these sub-processes, collectively Omodysplasia disrupts normal skeletal system development (GO:0001501) and cartilage/bone maturation at multiple stages.
Morphogen gradient formation: Though not a formal GO term, it’s worth noting that Omodysplasia illustrates problems in morphogen distribution. Glypican-6 normally helps establish proper gradients of Hedgehog in the growth plate microenvironment (pmc.ncbi.nlm.nih.gov). In its absence, the spatial-temporal pattern of IHH signaling is likely altered. Indeed, heparan sulfate proteoglycans (like GPC6) “play a role in regulating essential developmental events, such as morphogen gradient formation” (pmc.ncbi.nlm.nih.gov). This general process underlies how signaling pathways orchestrate tissue patterning, and its disturbance is a theme in the disease.
Overall, Omodysplasia affects critical developmental biological processes: signaling pathways (Hh, Wnt), cartilage anlage formation, and ossification. This multi-level disruption in skeletogenesis explains the clinical features of the disease.
The molecular pathology of Omodysplasia unfolds at specific cellular locations and structures:
Plasma membrane (GO:0005886): Both glypican-6 and Frizzled-2 function at the cell surface. Glypican-6 is anchored to the external leaflet of the plasma membrane via a GPI anchor (pmc.ncbi.nlm.nih.gov), positioning its heparan sulfate chains to interact with extracellular ligands. Frizzled-2 is a transmembrane receptor spanning the plasma membrane, with an extracellular domain binding Wnt and an intracellular tail transmitting signals. The disease-causing FZD2 mutation truncates the intracellular tail, so the mutant receptor still localizes to the membrane and can bind Wnt ligand but cannot relay the signal inward (pmc.ncbi.nlm.nih.gov). Thus, the cell membrane is a key site: in OMOD1, the membrane is deficient in GPC6 co-receptors; in OMOD2, it bears non-functional FZD2 receptors. These defects at the plasma membrane compromise the initiation of Hedgehog and Wnt signaling cascades.
Primary cilium (GO:0031513): The primary cilium is a microtubule-based organelle on the surface of chondrocytes that acts as a hub for Hedgehog signal transduction. Patched-1 (PTCH1) and Smoothened localize to cilia to transduce Hedgehog signals once IHH is present. Recent research showed that glypican-6 shuttles to the cilium upon Hedgehog stimulation: “in the absence of Hh, GPC6 is localized outside of the cilium but moves into the cilium upon addition of Hh” (pmc.ncbi.nlm.nih.gov). GPC6 appears to facilitate the interaction of Hedgehog ligand with PTCH1 at the ciliary membrane (pmc.ncbi.nlm.nih.gov). In GPC6-null cells, Hedgehog cannot effectively activate signaling in the cilium, as evidenced by loss of downstream Gli activation (pmc.ncbi.nlm.nih.gov). Therefore, the primary cilium of growth plate chondrocytes is a critical cellular component impacted by Omodysplasia – without GPC6, the Hedgehog reception in cilia is blunted. (Notably, ciliary dysfunction is not primary here, but the lack of a co-receptor in cilia has a similar outcome: reduced Hh pathway output.)
Extracellular matrix (GO:0031012): The cartilage extracellular matrix (ECM) is the milieu where signaling molecules diffuse and act. Glypican-6, via its heparan sulfate chains, is a component of the pericellular matrix that sequesters and presents growth factors. In OMOD1, the ECM in the growth plate lacks functional GPC6, likely altering the distribution of IHH and possibly other growth factors (FGFs, BMPs) that bind HSPGs (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). The absence of GPC6 in the matrix may lead to rapid diffusion or uneven gradients of Hedgehog, failing to properly maintain the proliferative vs. hypertrophic zones of cartilage. Additionally, the ECM component chondroitin sulfate can also influence growth plate signaling, but it’s the deficit of the heparan sulfate proteoglycan that is central in this disease. In summary, the ECM immediately around chondrocytes is a key compartment – Omodysplasia perturbs the normal ECM-morphogen interactions necessary for organized ossification.
Cytoskeleton/Dishevelled puncta: In OMOD2, an interesting cellular phenotype is observed in the cytoplasm regarding Dishevelled (DVL) localization. In unstimulated cells, DVL is found in cytosolic punctate complexes. When Wnt binds to a Frizzled receptor, DVL relocates to the plasma membrane to propagate the signal. In cells expressing mutant FZD2, recruitment of DVL to the membrane upon Wnt stimulation is greatly reduced (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Microscopy showed that with Wnt, wild-type FZD2 co-localizes with DVL at the membrane, whereas FZD2^Trp548* fails to recruit DVL, leaving DVL in cytosolic puncta (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). This suggests that the cytosolic signalosome assembly (a complex of FZD–DVL–Axin, etc.) at the inner leaflet of the membrane is defective. So while not a specific organelle, the subcellular localization of signal proteins (membrane vs cytosol) is an important cellular component aspect – Omodysplasia involves failure to form the membrane-associated Wnt signalosome due to the truncated FZD2.
In summary, Omodysplasia’s molecular defects manifest at the cell surface (membrane receptors/co-receptors), within specialized surface organelles (primary cilium for Hh signaling), and in the extracellular space (matrix ligand distribution). These disrupted cellular component locales underlie the breakdown of intercellular communication required for normal skeletal morphogenesis.
Omodysplasia is a developmental disorder present from birth, so its “progression” is best understood as a series of events during growth rather than a degenerative timeline. The initiating event is the inheritance (or de novo occurrence) of a pathogenic mutation in GPC6 or FZD2 at conception. This genetic defect sets off an abnormal developmental program in the embryo. During early embryogenesis, limb bud formation and skeletal patterning are altered due to impaired signaling. For instance, in FZD2-related cases, the limb buds may already exhibit abnormal proximal-distal patterning, contributing to humeral shortening. As endochondral ossification commences in the fetus, the effects become pronounced: by mid-gestation (~20 weeks), prenatal ultrasound can detect markedly shortened long bones (rhizomelia) in severe cases (pmc.ncbi.nlm.nih.gov). Bayat et al. (2020) reported a family where a routine 21-week scan showed severe shortening of all limbs in an affected fetus (pmc.ncbi.nlm.nih.gov). Thus, the disease process is active in utero, with insufficient growth plate expansion and bone formation from the second trimester onward.
At birth, the clinical phenotype is fully manifest: infants present with disproportionate short stature (short limbs with relatively normal trunk) and characteristic facial features. Birth length is often far below the typical range (one reported OMOD1 neonate was 45 cm at term, <<1st percentile (pmc.ncbi.nlm.nih.gov)). Despite the skeletal abnormalities, newborns are usually medically stable (weight can be near normal, and vital organ function is generally intact aside from occasional heart defects). Postnatally, the disease does not “progress” in the sense of new systems failing, but the consequences of the developmental anomalies persist. During childhood, the growth velocity of long bones remains low because the fundamental signaling deficits continue to limit chondrocyte function. This leads to short stature becoming more pronounced over time (final adult heights in recessive Omodysplasia range ~132–144 cm, about −5 to −7 SD below mean height) (pmc.ncbi.nlm.nih.gov). The limb deformities (e.g. elbow dislocations, bowed radii) may become more functionally significant as the child grows and tries to use their limbs, sometimes requiring orthopedic interventions.
Omodysplasia does not typically have distinct clinical stages; it is relatively static after the growth period is complete. One might consider the infancy/childhood phase (when growth plates are open) as the period where the skeletal differences emerge and increase relative to peers, followed by an adult phase where stature is fixed and secondary complications may appear. For instance, limited joint mobility in elbows and knees can lead to muscle contractures if not managed with physiotherapy. There is no evidence of progressive degeneration in bones – the bones are abnormal in shape/size but not known to deteriorate or fracture pathologically (unless secondary osteoporosis occurs in older age, which hasn’t been reported specifically for Omodysplasia). Intellectual development is usually normal, though a few cases of developmental delay are noted in the recessive form (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov) – this may be related to other congenital issues or mild structural brain differences, but data are sparse. Life expectancy is not well-documented due to the rarity, but patients have been reported into adulthood (pmc.ncbi.nlm.nih.gov). In summary, the “progression” is chiefly the unfolding of developmental abnormalities: from a genetic lesion to aberrant embryonic skeletal patterning, to detectable fetal bone shortening, to neonatal dwarfism, and finally to short-statured adulthood with possible orthopedic challenges. There are no phases of remission or relapse – the condition is continuously present from womb to adult life, defined by the consequences of early developmental disruptions.
Omodysplasia’s clinical phenotype centers on the skeleton, with secondary effects in other systems. Key manifestations and their mechanistic underpinnings include:
Disproportionate Short Stature (Rhizomelic dwarfism): Almost all patients have significantly short stature primarily due to shortened proximal long bones (rhizomelia). This phenotype directly reflects impaired endochondral ossification in the humeri and femora. The arms and thighs are much shorter than normal, while the head and trunk are relatively normal in size. In recessive OMOD1, both upper and lower limbs are severely affected, leading to very short overall height (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). In dominant OMOD2, the short stature may be mild or borderline (some patients have near-normal height), with a more pronounced effect in the arms (pubmed.ncbi.nlm.nih.gov). For example, an OMOD2 case had normal stature but clearly shortened humeri and restricted elbow movement (pubmed.ncbi.nlm.nih.gov). The rhizomelic shortening is a direct consequence of reduced chondrocyte proliferation in the growth plate – fewer and thinner growth plate columns yield shorter bones.
Limb Abnormalities and Joint Limitations: Beyond length, the shape of bones and joints is altered. Distal tapering of long bones (club-like flaring of the metaphyses) is often noted on X-rays (pmc.ncbi.nlm.nih.gov). The elbows are characteristically abnormal: many patients have proximal radioulnar diastasis with radial head dislocation (pubmed.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). This leads to limited extension and rotation at the elbow. The mechanism is that improper signaling during elbow joint formation (which involves segmented growth of radius/ulna) leads to malformed joint surfaces. Cubitus varus (inward angulation of elbow) may be seen. The knees can also be stiff with limited range, partly due to shortened distal femur and fibular bowing. In some cases, contractures or pterygia (webbing) at the knees and elbows were reported (pmc.ncbi.nlm.nih.gov), likely secondary to reduced motion in utero. Hands and feet: OMOD2 often shows a short first metacarpal, causing a form of brachydactyly (the thumb appears proximally placed) (www.ncbi.nlm.nih.gov). OMOD1 hands can be relatively normal or mildly shortened. Overall, limb joint limitations reflect the underlying structural abnormalities in bone geometry caused by dysregulated growth plate development.
Craniofacial Dysmorphism: Characteristic facial features are present, especially in OMOD1. These include frontal bossing (prominent forehead), a somewhat bulbous broad face, depressed nasal bridge with a short nose and anteverted (upturned) nostrils, and a long prominent philtrum (pubmed.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Hypertelorism (wide-spaced eyes) and relative macrocephaly (large-appearing head due to short stature) are sometimes noted (pubmed.ncbi.nlm.nih.gov). Newborns can have a frontal capillary hemangioma (stork bite or nevus flammeus on the forehead) in some cases (pmc.ncbi.nlm.nih.gov), although this is a minor finding. The craniofacial anomalies have parallels to Robinow syndrome (another short-limb condition involving Wnt5A/ROR2), underlining the Wnt-signaling disturbance in OMOD2 (pubmed.ncbi.nlm.nih.gov). Mechanistically, insufficient Wnt signaling via FZD2 in craniofacial mesenchyme likely leads to midface hypoplasia and the nasal bridge defect. Likewise, Hedgehog signaling (particularly Sonic hedgehog) is critical in facial patterning; glypican-6 loss might subtly affect SHH gradients in the developing face, contributing to these dysmorphic features (pmc.ncbi.nlm.nih.gov). Notably, in OMOD2 (FZD2 mutations), the craniofacial phenotype can closely resemble mild autosomal dominant Robinow syndrome (frontal bossing, nasal bridge depression, etc.) (pubmed.ncbi.nlm.nih.gov), consistent with disruption of Wnt/planar cell polarity pathways.
Chest and Spine: The axial skeleton is generally less affected. Spine length is relatively preserved (no significant dwarfism of the spine), and there are no consistent vertebral anomalies reported in Omodysplasia. Scoliosis is not a known feature. The chest may appear normal; however, some patients have been noted to have pectus carinatum or excavatum in other short-limb syndromes, but this isn’t emphasized in OMOD literature. Radiologically, no major vertebral segmentation defects or rib abnormalities have been described (pmc.ncbi.nlm.nih.gov). This contrasts with some other skeletal dysplasias, highlighting that Omodysplasia’s effects are mostly appendicular and craniofacial.
Genitourinary Anomalies: A subset of patients, especially males with recessive OMOD1, exhibit cryptorchidism (undescended testicles) (pmc.ncbi.nlm.nih.gov). This was present in the first reported families and is considered part of the phenotype variability (pmc.ncbi.nlm.nih.gov). Cryptorchidism could result from impaired androgen-driven gubernaculum development or abdominal pressure issues; however, since it’s not in all cases, it might reflect Wnt pathway roles in gonadal descent (Wnt5a is known to influence reproductive tract development). Some patients also have kidney or urinary tract anomalies reported anecdotally, but data is scarce. In OMOD2, hypoplastic genitalia or anomalies were mentioned as “variable genitourinary anomalies” in the original description (www.ncbi.nlm.nih.gov), though not in every case. For example, one male patient had cryptorchidism, while another had normal genital development (www.ncbi.nlm.nih.gov). These features indicate that while not the core of the disease, developmental pathways affected by GPC6/FZD2 can extend to the genitourinary system.
Cardiac and Other Organ Systems: There have been few reports of congenital heart defects in Omodysplasia (pmc.ncbi.nlm.nih.gov). Specifically, conditions like coarctation of the aorta, atrial septal defect (ASD), patent ductus arteriosus (PDA), or valve anomalies were noted in some cases of OMOD1 (pmc.ncbi.nlm.nih.gov). In the 2009 series, 2 of 8 patients had heart defects (pmc.ncbi.nlm.nih.gov). While not every patient is affected, these occurrences suggest that the genetic defect might subtly impact cardiac morphogenesis (possibly through impaired signaling in cardiac neural crest or endocardial cushion cells, where Hh/Wnt also play roles). No consistent gastrointestinal or pulmonary abnormalities have been tied to Omodysplasia.
Neurological and Cognitive: Omodysplasia is primarily a bone disorder, and most patients have normal intelligence and no major neurological deficits. However, variable developmental delay and mild intellectual disability were reported in a few of the early recessive cases (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). For instance, Campos-Xavier et al. mentioned “variable developmental delay” among their cases (pmc.ncbi.nlm.nih.gov). It’s unclear if this is due to the genetic defect’s effect on brain development or secondary to other issues (like chronic medical concerns or less optimal social development). Glypicans are expressed in the central nervous system and involved in neurodevelopmental signaling gradients (pmc.ncbi.nlm.nih.gov), so in theory a GPC6 mutation might have minor CNS effects. A recent case report (Das et al., 2024) even described an adult with Omodysplasia and treatment-resistant schizophrenia (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov), speculating on a link between the Wnt/Hedgehog pathway genes and neurodevelopment. However, this appears to be an isolated case; no definitive neurobehavioral phenotype is established for Omodysplasia (pmc.ncbi.nlm.nih.gov). Occasionally noted are hypotonia and motor delay in infancy (likely due to the orthopedic limitations). Seizures or major CNS malformations are not typical. In summary, most individuals with Omodysplasia do not have significant cognitive impairment, though a few have had mild delays, and rare psychiatric comorbidity has been observed anecdotally.
In conclusion, the phenotype of Omodysplasia spans primarily skeletal abnormalities – short limbs, joint dysplasia, facial dysmorphism – with occasional extraskeletal features like heart defects or cryptorchidism. These clinical manifestations align with the underlying molecular mechanisms: disrupted Hedgehog and Wnt signaling during development leads to errors in bone growth and patterning, which manifest as the unique constellation of Omodysplasia features. Each phenotypic trait, from rhizomelic short stature to craniofacial features, can be traced back to the developmental pathways derailed by GPC6 or FZD2 mutations. The rarity of the condition (fewer than 30 reported AR cases by 2009 (pmc.ncbi.nlm.nih.gov) and only ~10 AD cases by 2022 (pubmed.ncbi.nlm.nih.gov)) underscores that our understanding of the full phenotype spectrum is still evolving. Recent studies, such as a 2023 report of five siblings with a mild missense GPC6 variant, have expanded the known phenotype to include milder rhizomelia with partial function retained (pubmed.ncbi.nlm.nih.gov) (pubmed.ncbi.nlm.nih.gov). Those findings support the correlation between the molecular severity and clinical severity: even a hypomorphic GPC6 mutation that somewhat reduces Hedgehog signaling can cause short stature, albeit less extreme (pubmed.ncbi.nlm.nih.gov). Thus, Omodysplasia provides a clear example of how perturbation of key signaling pathways in the embryo leads to predictable abnormalities in anatomy and growth, and ongoing research and case reports continue to refine the genotype–phenotype correlations in this rare skeletal dysplasia.
Evidence: The pathophysiological insights above are supported by numerous studies. Campos-Xavier et al., 2009 (American Journal of Human Genetics) first identified GPC6 mutations as the cause of recessive Omodysplasia and documented the loss of function in endochondral ossification (pmc.ncbi.nlm.nih.gov). Saal et al., 2015 (Human Molecular Genetics) discovered the FZD2 mutation in dominant Omodysplasia and demonstrated its impact on Wnt signaling using cell-based assays (pmc.ncbi.nlm.nih.gov). Capurro et al., 2017 (J Cell Biol) provided mechanistic evidence in Gpc6-knockout mice that glypican-6 enhances Hedgehog signaling at the primary cilium (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). A 2020 case report by Bayat et al. described novel GPC6 variants and prenatal presentation (pmc.ncbi.nlm.nih.gov). Most recently, Crenshaw et al., 2023 (Am J Med Genet) reported a milder phenotype with a partial-function GPC6 mutation, confirmed via Hedgehog activity assays (pubmed.ncbi.nlm.nih.gov) (pubmed.ncbi.nlm.nih.gov). These and other references furnish a consistent picture of Omodysplasia’s molecular basis and clinical manifestations, solidifying our current understanding of this rare skeletal disorder.