👪

Inheritance

2

Autosomal Dominant Inheritance (mEDS Dominant) HP:0000006

The milder end of the spectrum (mEDS Dominant subtype) is typically caused by a heterozygous, often de novo, COL12A1 variant.

Autosomal dominant inheritance

Show evidence (1 reference)

PMID:24334604 SUPPORT Human Clinical

"a de novo dominant mutation in collagen XII (COL12A1) as underlying a novel overlap syndrome involving muscle and connective tissue"

Documents a de novo heterozygous COL12A1 variant causing the dominant form.

Autosomal Recessive Inheritance (mEDS Recessive) HP:0000007

The severe end of the spectrum (mEDS Recessive subtype) is caused by biallelic (homozygous or compound heterozygous) loss-of-function COL12A1 variants.

Autosomal recessive inheritance

Show evidence (1 reference)

PMID:39923201 SUPPORT Human Clinical

"Next-generation-based sequencing identified rare biallelic COL12A1 (NM_004370.6) variants in all eight patients."

Confirms biallelic COL12A1 variants as the cause of the recessive severe phenotype.

◆

Subtypes

2

mEDS (dominant, Bethlem myopathy 2 spectrum) MONDO:0034022

COL12A1 hgnc:2188

Caused by heterozygous, often de novo, missense or in-frame exon-skipping COL12A1 variants. The milder, more common end of the spectrum, presenting with joint hypermobility, congenital hypotonia, and proximal/axial muscle weakness that is typically non-progressive or slowly progressive.

Show evidence (1 reference)

PMID:24334604 SUPPORT Human Clinical

"the patient with the de novo missense mutation was more mildly affected, showing improvement including the acquisition of walking"

Founding paper describes the milder dominant phenotype associated with a de novo heterozygous COL12A1 variant.

mEDS (recessive, Ullrich congenital muscular dystrophy 2 spectrum) MONDO:0014654

COL12A1 hgnc:2188

Caused by biallelic (homozygous or compound heterozygous) loss-of-function COL12A1 variants. The more severe end of the spectrum, presenting at birth with profound weakness, arthrogryposis, and respiratory/feeding difficulties.

Show evidence (1 reference)

PMID:39923201 SUPPORT Human Clinical

"further establishing COL12A1 as a recessive myopathic Ehlers-Danlos syndrome (mEDS) gene, and expanding the clinical spectrum to include a milder EDS phenotype"

Establishes biallelic COL12A1 variants as causing the recessive, more severe end of the mEDS spectrum.

⚙

Pathophysiology

7

COL12A1 Dominant Variant

Heterozygous, often de novo, missense or in-frame exon-skipping variants cluster to the thrombospondin N-terminal region and adjacent collagenous domain, causing variant-specific intracellular accumulation of collagen XII chains and extracellular overmodification of the long isoform.

COL12A1 hgnc:2188

Genetic context variant_origin: GERMLINE zygosity: HETEROZYGOUS functional_impact_category: DOMINANT_NEGATIVE

Downstream

Depleted Collagen XII-Bridged Extracellular Matrix Intracellularly retained and structurally abnormal collagen XII fails to properly bridge collagen I fibrils with decorin and tenascin-X in the extracellular space.

Show evidence (1 reference)

PMID:31273343 SUPPORT Human Clinical

"Variant-specific intracellular accumulation of collagen XII chains, extracellular overmodification of the long isoform and near-absence of the short isoform of collagen XII, and extracellular decrease of decorin and tenascin-X were observed for the COL12A1 variants."

Directly demonstrates the cellular and extracellular consequences of heterozygous COL12A1 exon-skipping variants.

COL12A1 Biallelic Loss-of-Function

Homozygous or compound heterozygous loss-of-function (splice-site, truncating) COL12A1 variants abolish or severely reduce collagen XII protein expression, ranging from complete absence in severe disease to mild reduction in milder biallelic disease.

COL12A1 hgnc:2188

Genetic context variant_origin: GERMLINE zygosity: HOMOZYGOUS functional_impact_category: LOSS_OF_FUNCTION

Downstream

Depleted Collagen XII-Bridged Extracellular Matrix Absent or severely reduced collagen XII removes the molecular bridge between collagen I fibrils and other matrix components.

Show evidence (1 reference)

PMID:39923201 SUPPORT In Vitro

"in vitro immunocytochemistry analysis in fibroblasts ranged from complete absence of Collagen XII expression in a patient with severe disease, to a mild reduction in a patient with milder disease"

Demonstrates a genotype-severity correlation in collagen XII protein expression across the biallelic spectrum.

Depleted Collagen XII-Bridged Extracellular Matrix

Loss of the collagen XII bridge between collagen I fibrils and accessory extracellular matrix proteins secondarily depletes extracellular decorin and tenascin-X, destabilizing the connective tissue matrix of muscle endomysium/perimysium, joint capsules, and skin.

collagen fibril organization GO:0030199 ↓ DECREASED

skeletal muscle tissue UBERON:0001134

Downstream

Impaired Muscle Force Transmission Destabilized endomysial/perimysial connective tissue matrix impairs passive force transmission through skeletal muscle.

Joint and Skin Connective Tissue Laxity Destabilized joint capsule and dermal connective tissue matrix produces joint hypermobility and EDS-type skin findings.

Cardiac Valve Connective Tissue Involvement The same collagen XII-bridged ECM defect operating in cardiac valve leaflet connective tissue produces valvular anomalies.

Craniofacial and Dysmorphic Features A cluster of dysmorphic craniofacial findings recurs alongside the core muscle/joint phenotype in the severe biallelic cohort; the specific mechanistic link to the collagen XII/ECM defect is not yet established in the cited source, so this edge records only that both arise from the same underlying disorder, not a specific causal step.

Show evidence (1 reference)

PMID:31273343 SUPPORT Human Clinical

"extracellular decrease of decorin and tenascin-X were observed for the COL12A1 variants"

Directly demonstrates secondary depletion of decorin and tenascin-X in patient-derived material with COL12A1 variants.

Impaired Muscle Force Transmission

A Col12a1-null mouse model shows decreased grip strength, a delay in muscle fiber-type transition, and a deficiency in passive force generation, indicating that the matrix-based passive force-transducing elastic element normally provided by collagen XII is disrupted.

skeletal muscle fiber CL:0008002

Downstream

Proximal and Axial Muscle Weakness

Congenital Hypotonia

Skeletal Muscle Atrophy Chronic impaired force generation and disuse lead to secondary skeletal muscle atrophy, characteristically of the rectus femoris.

Motor Delay Impaired force generation delays acquisition of gross motor milestones.

Kyphoscoliosis Weakness of paraspinal musculature contributes to progressive spinal curvature.

Show evidence (1 reference)

PMID:24334604 SUPPORT Model Organism

"A mouse model with inactivation of the Col12a1 gene showed decreased grip strength, a delay in fiber-type transition and a deficiency in passive force generation while the muscle seems more resistant to eccentric contraction induced force drop, indicating a role for a matrix-based passive..."

Directly demonstrates the mechanistic link between collagen XII loss and impaired muscle force generation in a Col12a1-null mouse model.

Joint and Skin Connective Tissue Laxity

Destabilized joint capsule connective tissue produces distal joint hypermobility and, in the severe biallelic form, congenital joint contractures and arthrogryposis reflecting a mixed laxity/contracture phenotype.

Downstream

Distal Joint Hypermobility

Arthrogryposis

Hip Dysplasia Congenital joint laxity/instability predisposes to hip dysplasia.

Talipes Equinovarus Congenital joint contracture affecting the ankle/foot produces talipes equinovarus.

Show evidence (1 reference)

PMID:39923201 SUPPORT Human Clinical

"Distal joint laxity was noted in all patients (Fig. 1A–C), typically affecting wrists and ankles. Concurrent joint contractures were present in six patients and typically affected the long finger flexors"

Documents the combined joint-laxity-plus-contracture pattern characteristic of the severe biallelic phenotype.

Cardiac Valve Connective Tissue Involvement

Destabilized valve leaflet connective tissue produces mild valvular anomalies including leaflet thickening, dysplasia, and regurgitation, reported in a subset of the severe biallelic cohort.

cardiac valve UBERON:0000946

Downstream

Mitral Regurgitation

Show evidence (1 reference)

PMID:39923201 SUPPORT Human Clinical

"Four patients also had evidence of cardiac involvement, with one (F2P2) presenting with Wolff–Parkinson–White syndrome."

Documents cardiac involvement, including valvular anomalies, in a subset of the severe biallelic cohort.

Craniofacial and Dysmorphic Features

Dysmorphic craniofacial findings, evident in all patients of the severe biallelic cohort, recur alongside the core connective-tissue/muscle phenotype. The specific mechanistic link between the collagen XII/ECM defect and these findings is not established in the cited source.

Downstream

Micrognathia

Gingival Overgrowth

Show evidence (1 reference)

PMID:39923201 SUPPORT Human Clinical

"Dysmorphic features were evident in all patients."

Establishes dysmorphic craniofacial features as a consistent finding in the severe biallelic cohort.

⬡

Pathograph

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

●

Phenotypes

12

Cardiovascular 1

Mitral Regurgitation HP:0001653

Show evidence (1 reference)

PMID:39923201 SUPPORT Human Clinical

"F1P1 and F3P3 had echocardiograms in infancy showing mild valvular anomalies with thickened mitral valve leaflets and mild-to-moderate mitral regurgitation in F1P1 and dysplastic mitral and tricuspid valves with redundant tissue and mild mitral valve regurgitation in F3P3"

Documents mitral regurgitation with valve dysplasia in two patients of the severe biallelic cohort. (Note -- a third patient, F2P2, is separately tabulated with "MVP" i.e. true mitral valve prolapse, per Table 1's legend; that is a distinct finding not evidenced by this quote, so this phenotype is scoped to the regurgitation/dysplasia finding the quote actually supports.)

Head and Neck 2

Gingival Overgrowth HP:0000212

Show evidence (1 reference)

PMID:39923201 SUPPORT Human Clinical

"Other common findings included micrognathia (n = 4), gingival hypertrophy (n = 6)"

Documents gingival hypertrophy in 6 of 8 patients in the severe biallelic cohort, a dysmorphic feature distinguishing mEDS from typical EDS subtypes.

Micrognathia HP:0000347

Show evidence (1 reference)

PMID:39923201 SUPPORT Human Clinical

"Other common findings included micrognathia (n = 4), gingival hypertrophy (n = 6)"

Documents micrognathia in 4 of 8 patients in the severe biallelic cohort.

Limbs 1

Talipes Equinovarus HP:0001762

Show evidence (1 reference)

PMID:39923201 SUPPORT Human Clinical

"Congenital hip dysplasia Talipes equinovarus"

Listed as a presenting congenital orthopedic finding (alongside hip dysplasia) in one patient of the severe biallelic cohort.

Musculoskeletal 7

Proximal and Axial Muscle Weakness Proximal muscle weakness HP:0003701

Show evidence (1 reference)

PMID:40508193 SUPPORT Human Clinical

"present a combination of joint hypermobility and axial, distal, and proximal weakness"

Documents combined axial, distal, and proximal muscle weakness as the core myopathic phenotype of mEDS.

Skeletal Muscle Atrophy HP:0003202

Show evidence (1 reference)

PMID:40508193 SUPPORT Human Clinical

"confirming the characteristic atrophy of the rectus femoris"

Documents rectus femoris muscle atrophy as a characteristic imaging finding in mEDS.

Congenital Hypotonia HP:0001252

Show evidence (1 reference)

PMID:39923201 SUPPORT Human Clinical

"All patients presented with congenital onset symptoms including reduced fetal movement, hypotonia, and hip dysplasia"

Documents congenital hypotonia as a core presenting feature of the severe biallelic phenotype.

Distal Joint Hypermobility HP:0020152

Show evidence (1 reference)

PMID:39923201 SUPPORT Human Clinical

"Distal joint laxity was noted in all patients (Fig. 1A–C), typically affecting wrists and ankles."

Documents distal joint hypermobility/laxity in all patients of the biallelic cohort.

Arthrogryposis Arthrogryposis multiplex congenita HP:0002804

Show evidence (1 reference)

PMID:39923201 SUPPORT Human Clinical

"four patients (F1P1, F2P2, F3P3 and F4P4) presenting with arthrogryposis"

Documents arthrogryposis in a subset of the severe biallelic cohort.

Hip Dysplasia HP:0001385

Show evidence (1 reference)

PMID:39923201 SUPPORT Human Clinical

"All patients presented with congenital onset symptoms including reduced fetal movement, hypotonia, and hip dysplasia"

Documents congenital hip dysplasia as a core presenting feature of the severe biallelic phenotype.

Kyphoscoliosis HP:0002751

Show evidence (1 reference)

PMID:39923201 SUPPORT Human Clinical

"F1P1 and F3P3 were noted to have progressive thoracic kyphoscoliosis"

Documents progressive kyphoscoliosis as a musculoskeletal complication in the biallelic cohort.

Nervous System 1

Motor Delay HP:0001270

Show evidence (1 reference)

PMID:39923201 SUPPORT Human Clinical

"All patients had delayed acquisition of motor milestones."

Documents delayed motor milestone acquisition across the biallelic cohort.

🧬

Genetic Associations

1

COL12A1

Gene: COL12A1 hgnc:2188

Show evidence (1 reference)

PMID:39923201 SUPPORT Human Clinical

"COLXII is a homotrimer assembled from three COLXII alpha chains encoded by COL12A1. It is essential for collagen fibril organization by bridging Collagen I-containing fibrils bound at the collagenous domain with various extracellular matrix (ECM) proteins including tenascin-X."

Describes the normal molecular function of collagen XII.

💊

Medical Actions

4

Orthopedic Management of Scoliosis and Joint Contractures

Action: Orthopedic Surgical Procedure NCIT:C16186

Platform: Surgery

Orthopedic surveillance and surgical correction of progressive kyphoscoliosis and joint contractures, most often required in the more severe mEDS Recessive phenotype.

Mechanism Target:

MODULATES Kyphoscoliosis — Surgical instrumentation mechanically stabilizes and corrects the progressive spinal curvature; it addresses the structural consequence of muscle weakness and connective-tissue laxity rather than the underlying collagen XII defect.

Show evidence (1 reference)

PMID:39923201 SUPPORT Human Clinical

"F2P2, F6P7 and F7P8 had progressive scoliosis requiring spinal surgery at age 10 years in F2P2."

Documents spinal surgery for progressive scoliosis in the biallelic (mEDS Recessive) cohort.

Respiratory Support (Noninvasive to Invasive Mechanical Ventilation)

Action: Mechanical Ventilation NCIT:C70909

Platform: Device

Escalating respiratory support ranging from noninvasive ventilation to tracheostomy and ventilator dependency, reflecting the variable severity of respiratory muscle involvement across the mEDS spectrum.

Mechanism Target:

MODULATES Proximal and Axial Muscle Weakness — Supports ventilation when respiratory muscle weakness becomes severe enough to compromise breathing; it does not correct the underlying muscle force-transmission defect.

Show evidence (2 references)

PMID:39923201 SUPPORT Human Clinical

"Respiratory involvement was variable, ranging from none to tracheostomy and ventilatory dependency since birth (F6P7)."

Documents the range of respiratory support required in the biallelic (mEDS Recessive) cohort, from none to lifelong ventilator dependency.

PMID:40508193 SUPPORT Human Clinical

"Three out of 10 UCMD2 patients began non-invasive ventilation (NIV) before the age of 3"

Documents early noninvasive ventilation initiation in a subset of UCMD2 (mEDS Recessive) patients, drawn from a systematic literature review.

Nutritional Support (Nasogastric or Gastrostomy Feeding)

Action: Nutritional Support NCIT:C15433

Platform: Other

Enteral feeding support for neonatal feeding difficulties arising from congenital hypotonia and weakness, common in the severe mEDS Recessive phenotype.

Mechanism Target:

MODULATES Congenital Hypotonia — Provides enteral nutrition when hypotonia-related feeding difficulty makes oral intake unsafe or insufficient; it does not correct the underlying hypotonia itself.

Show evidence (1 reference)

PMID:39923201 SUPPORT Human Clinical

"Neonatal feeding difficulties were present in seven, requiring a nasogastric or gastrostomy tube placement."

Documents enteral feeding support for neonatal feeding difficulty in the biallelic (mEDS Recessive) cohort.

Genetic Counseling

Action: Genetic Counseling NCIT:C15240

Genetic counseling regarding the dominant (typically de novo) or recessive (biallelic) inheritance pattern, recurrence risk, and availability of carrier and prenatal/preimplantation testing.

Show evidence (2 references)

PMID:24334604 SUPPORT Human Clinical

"a de novo dominant mutation in collagen XII (COL12A1) as underlying a novel overlap syndrome involving muscle and connective tissue"

Documents the typically de novo dominant inheritance relevant to counseling for mEDS Dominant.

PMID:39923201 SUPPORT Human Clinical

"Next-generation-based sequencing identified rare biallelic COL12A1 (NM_004370.6) variants in all eight patients."

Documents the biallelic recessive inheritance relevant to counseling for mEDS Recessive, including carrier-testing implications for relatives.

🔬

Diagnosis

2

Molecular Genetic Testing

Diagnosis is established by identifying a heterozygous (dominant) or biallelic (recessive) pathogenic COL12A1 variant in an individual with suggestive combined muscle/connective-tissue clinical findings.

Show evidence (1 reference)

PMID:39923201 SUPPORT Human Clinical

"Next-generation-based sequencing identified rare biallelic COL12A1 (NM_004370.6) variants in all eight patients."

Describes the molecular diagnostic approach used to confirm biallelic COL12A1-related disease.

Dermal Fibroblast Immunostaining

Immunocytochemistry of patient-derived dermal fibroblasts for collagen XII expression can support a diagnosis and correlates with clinical severity, ranging from complete absence in severe disease to mild reduction in milder disease.

Show evidence (1 reference)

PMID:39923201 SUPPORT In Vitro

"in vitro immunocytochemistry analysis in fibroblasts ranged from complete absence of Collagen XII expression in a patient with severe disease, to a mild reduction in a patient with milder disease"

Describes dermal fibroblast immunostaining as a supportive diagnostic tool correlating with disease severity.

📊

Prevalence

1

Worldwide

Cases In Literature Ultra Rare

13 patients with heterozygous or homozygous COL12A1 variants reported in the literature as of the 2020 cohort-expansion study.

Show evidence (1 reference)

PMID:31273343 SUPPORT Human Clinical

"heterozygous or homozygous COL12A1 variants have been reported in 13 patients presenting with a clinical phenotype overlapping with collagen VI-related myopathies and Ehlers-Danlos syndrome (EDS)"

Reports the cumulative literature case count for COL12A1-related mEDS at time of publication.

{ }

Source YAML

click to show

name: Myopathic Ehlers-Danlos Syndrome
category: Mendelian
creation_date: "2026-09-16T17:43:16Z"
description: >
  Myopathic Ehlers-Danlos syndrome (mEDS) is a connective-tissue/muscle
  overlap disorder caused by heterozygous (dominant) or biallelic
  (recessive) pathogenic variants in COL12A1, which encodes collagen XII, a
  fibril-associated collagen with interrupted triple helices (FACIT) that
  bridges collagen I-containing fibrils with other extracellular matrix
  components, including decorin and tenascin-X. The disorder spans a
  clinical spectrum: the milder, typically dominant end (historically termed
  Bethlem myopathy 2, an exact synonym of mEDS) presents with congenital
  hypotonia, proximal joint contractures, distal joint hypermobility, and
  progressive proximal and axial muscle weakness; the more severe, typically
  recessive end (Ullrich congenital muscular dystrophy 2) presents at birth
  with profound weakness, arthrogryposis, and respiratory insufficiency.
  Reduced or structurally abnormal collagen XII secondarily depletes
  extracellular decorin and tenascin-X, the same two matrix proteins whose
  primary loss drives classical-like EDS (TNXB) -- a mechanistic parallel
  between the two disorders' convergent effects on the matrix, not a
  structural link between the two dismech entries themselves.
disease_term:
  preferred_term: Myopathic Ehlers-Danlos Syndrome
  term:
    id: MONDO:0034022
    label: Bethlem myopathy 2
synonyms:
- mEDS
- EDS, myopathic type
- Ehlers-Danlos syndrome, myopathic type
- Bethlem myopathy 2
- Collagen XII-related myopathic EDS
notes: >
  No GeneReviews chapter exists for myopathic EDS, COL12A1, Bethlem myopathy,
  or Ullrich congenital muscular dystrophy (searched PubMed genereviews[book]
  for each term; no hits). The disease_term is anchored on MONDO:0034022
  ("Bethlem myopathy 2"), whose exact synonyms include "EDS, myopathic type",
  "Ehlers-Danlos syndrome, myopathic type", and "myopathic EDS" -- MONDO does
  not carry a separate, EDS-labeled top-level term for this disease. The
  severe/recessive end of the same COL12A1 clinical spectrum is separately
  termed MONDO:0014654 ("Ullrich congenital muscular dystrophy 2") and is
  modeled here as a subtype rather than a distinct disease, consistent with
  how the primary literature describes a single genotype-correlated severity
  spectrum rather than two discrete conditions. kb/disorders/Ullrich_Congenital_Muscular_Dystrophy.yaml
  already has_subtypes a thin "UCMD2" entry anchored on the same MONDO:0014654,
  citing the same PMID:24334604 founding paper; that entry frames the disease
  through neuromuscular-disease classification (COL6A1/2/3 as the primary
  cause, COL12A1 as a rare phenocopy subtype), while this entry frames the
  same COL12A1 gene-disease relationship through the 2017 international EDS
  classification (mEDS as one of the 13 named EDS subtypes). Both are
  legitimate framings of the same underlying biology rather than an
  unintentional duplication; this entry is the more detailed, EDS-focused
  curation for COL12A1 specifically, spanning both the dominant and
  recessive ends of its spectrum.
parents:
- Ehlers-Danlos Syndrome
- Connective Tissue Disorder
references:
- reference: PMID:24334604
  title: "Recessive and dominant mutations in COL12A1 cause a novel EDS/myopathy overlap syndrome in humans and mice."
- reference: PMID:28306229
  title: "The 2017 international classification of the Ehlers-Danlos syndromes."
has_subtypes:
- name: mEDS Dominant
  display_name: mEDS (dominant, Bethlem myopathy 2 spectrum)
  subtype_term:
    preferred_term: Bethlem myopathy 2
    term:
      id: MONDO:0034022
      label: Bethlem myopathy 2
  genes:
  - preferred_term: COL12A1
    term:
      id: hgnc:2188
      label: COL12A1
  description: >
    Caused by heterozygous, often de novo, missense or in-frame exon-skipping
    COL12A1 variants. The milder, more common end of the spectrum, presenting
    with joint hypermobility, congenital hypotonia, and proximal/axial muscle
    weakness that is typically non-progressive or slowly progressive.
  evidence:
  - reference: PMID:24334604
    reference_title: "Recessive and dominant mutations in COL12A1 cause a novel EDS/myopathy overlap syndrome in humans and mice."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the patient with the de novo missense mutation was more mildly affected, showing improvement including the acquisition of walking"
    explanation: Founding paper describes the milder dominant phenotype associated with a de novo heterozygous COL12A1 variant.
- name: mEDS Recessive
  display_name: mEDS (recessive, Ullrich congenital muscular dystrophy 2 spectrum)
  subtype_term:
    preferred_term: Ullrich congenital muscular dystrophy 2
    term:
      id: MONDO:0014654
      label: Ullrich congenital muscular dystrophy 2
  genes:
  - preferred_term: COL12A1
    term:
      id: hgnc:2188
      label: COL12A1
  description: >
    Caused by biallelic (homozygous or compound heterozygous) loss-of-function
    COL12A1 variants. The more severe end of the spectrum, presenting at birth
    with profound weakness, arthrogryposis, and respiratory/feeding
    difficulties.
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "further establishing COL12A1 as a recessive myopathic Ehlers-Danlos syndrome (mEDS) gene, and expanding the clinical spectrum to include a milder EDS phenotype"
    explanation: Establishes biallelic COL12A1 variants as causing the recessive, more severe end of the mEDS spectrum.
prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: 13 patients with heterozygous or homozygous COL12A1 variants reported in the literature as of the 2020 cohort-expansion study.
  evidence:
  - reference: PMID:31273343
    reference_title: "Novel defects in collagen XII and VI expand the mixed myopathy/Ehlers-Danlos syndrome spectrum and lead to variant-specific alterations in the extracellular matrix."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "heterozygous or homozygous COL12A1 variants have been reported in 13 patients presenting with a clinical phenotype overlapping with collagen VI-related myopathies and Ehlers-Danlos syndrome (EDS)"
    explanation: Reports the cumulative literature case count for COL12A1-related mEDS at time of publication.
inheritance:
- name: Autosomal Dominant Inheritance (mEDS Dominant)
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  description: >
    The milder end of the spectrum (mEDS Dominant subtype) is typically
    caused by a heterozygous, often de novo, COL12A1 variant.
  evidence:
  - reference: PMID:24334604
    reference_title: "Recessive and dominant mutations in COL12A1 cause a novel EDS/myopathy overlap syndrome in humans and mice."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a de novo dominant mutation in collagen XII (COL12A1) as underlying a novel overlap syndrome involving muscle and connective tissue"
    explanation: Documents a de novo heterozygous COL12A1 variant causing the dominant form.
- name: Autosomal Recessive Inheritance (mEDS Recessive)
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >
    The severe end of the spectrum (mEDS Recessive subtype) is caused by
    biallelic (homozygous or compound heterozygous) loss-of-function COL12A1
    variants.
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Next-generation-based sequencing identified rare biallelic COL12A1 (NM_004370.6) variants in all eight patients."
    explanation: Confirms biallelic COL12A1 variants as the cause of the recessive severe phenotype.
genetic:
- name: COL12A1
  gene_term:
    preferred_term: COL12A1
    term:
      id: hgnc:2188
      label: COL12A1
  notes: >
    COL12A1 encodes collagen XII, a homotrimeric FACIT collagen that bridges
    collagen I-containing fibrils with extracellular matrix proteins
    including decorin and tenascin-X. Dominant variants (missense, in-frame
    exon-skipping) produce a milder phenotype; biallelic loss-of-function
    variants produce a more severe phenotype.
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "COLXII is a homotrimer assembled from three COLXII alpha chains encoded by COL12A1. It is essential for collagen fibril organization by bridging Collagen I-containing fibrils bound at the collagenous domain with various extracellular matrix (ECM) proteins including tenascin-X."
    explanation: Describes the normal molecular function of collagen XII.
pathophysiology:
- name: COL12A1 Dominant Variant
  biological_scale: MOLECULAR
  subtypes:
  - mEDS Dominant
  genetic_context:
    variant_origin: GERMLINE
    functional_impact_category: DOMINANT_NEGATIVE
    zygosity: HETEROZYGOUS
  genes:
  - preferred_term: COL12A1
    term:
      id: hgnc:2188
      label: COL12A1
  description: >
    Heterozygous, often de novo, missense or in-frame exon-skipping variants
    cluster to the thrombospondin N-terminal region and adjacent collagenous
    domain, causing variant-specific intracellular accumulation of collagen
    XII chains and extracellular overmodification of the long isoform.
  evidence:
  - reference: PMID:31273343
    reference_title: "Novel defects in collagen XII and VI expand the mixed myopathy/Ehlers-Danlos syndrome spectrum and lead to variant-specific alterations in the extracellular matrix."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Variant-specific intracellular accumulation of collagen XII chains, extracellular overmodification of the long isoform and near-absence of the short isoform of collagen XII, and extracellular decrease of decorin and tenascin-X were observed for the COL12A1 variants."
    explanation: Directly demonstrates the cellular and extracellular consequences of heterozygous COL12A1 exon-skipping variants.
  downstream:
  - target: Depleted Collagen XII-Bridged Extracellular Matrix
    description: Intracellularly retained and structurally abnormal collagen XII fails to properly bridge collagen I fibrils with decorin and tenascin-X in the extracellular space.
- name: COL12A1 Biallelic Loss-of-Function
  biological_scale: MOLECULAR
  subtypes:
  - mEDS Recessive
  genetic_context:
    variant_origin: GERMLINE
    functional_impact_category: LOSS_OF_FUNCTION
    zygosity: HOMOZYGOUS
  genes:
  - preferred_term: COL12A1
    term:
      id: hgnc:2188
      label: COL12A1
  notes: >-
    zygosity is recorded as HOMOZYGOUS (the slot is single-valued); the
    reported cohort is a mix of homozygous and compound heterozygous
    biallelic genotypes -- see description.
  description: >
    Homozygous or compound heterozygous loss-of-function (splice-site,
    truncating) COL12A1 variants abolish or severely reduce collagen XII
    protein expression, ranging from complete absence in severe disease to
    mild reduction in milder biallelic disease.
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "in vitro immunocytochemistry analysis in fibroblasts ranged from complete absence of Collagen XII expression in a patient with severe disease, to a mild reduction in a patient with milder disease"
    explanation: Demonstrates a genotype-severity correlation in collagen XII protein expression across the biallelic spectrum.
  downstream:
  - target: Depleted Collagen XII-Bridged Extracellular Matrix
    description: Absent or severely reduced collagen XII removes the molecular bridge between collagen I fibrils and other matrix components.
- name: Depleted Collagen XII-Bridged Extracellular Matrix
  biological_scale: TISSUE
  locations:
  - preferred_term: skeletal muscle tissue
    term:
      id: UBERON:0001134
      label: skeletal muscle tissue
  biological_processes:
  - preferred_term: collagen fibril organization
    term:
      id: GO:0030199
      label: collagen fibril organization
    modifier: DECREASED
  description: >
    Loss of the collagen XII bridge between collagen I fibrils and
    accessory extracellular matrix proteins secondarily depletes
    extracellular decorin and tenascin-X, destabilizing the connective
    tissue matrix of muscle endomysium/perimysium, joint capsules, and skin.
  evidence:
  - reference: PMID:31273343
    reference_title: "Novel defects in collagen XII and VI expand the mixed myopathy/Ehlers-Danlos syndrome spectrum and lead to variant-specific alterations in the extracellular matrix."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "extracellular decrease of decorin and tenascin-X were observed for the COL12A1 variants"
    explanation: Directly demonstrates secondary depletion of decorin and tenascin-X in patient-derived material with COL12A1 variants.
  downstream:
  - target: Impaired Muscle Force Transmission
    description: Destabilized endomysial/perimysial connective tissue matrix impairs passive force transmission through skeletal muscle.
  - target: Joint and Skin Connective Tissue Laxity
    description: Destabilized joint capsule and dermal connective tissue matrix produces joint hypermobility and EDS-type skin findings.
  - target: Cardiac Valve Connective Tissue Involvement
    description: The same collagen XII-bridged ECM defect operating in cardiac valve leaflet connective tissue produces valvular anomalies.
  - target: Craniofacial and Dysmorphic Features
    description: >-
      A cluster of dysmorphic craniofacial findings recurs alongside the
      core muscle/joint phenotype in the severe biallelic cohort; the
      specific mechanistic link to the collagen XII/ECM defect is not yet
      established in the cited source, so this edge records only that both
      arise from the same underlying disorder, not a specific causal step.

- name: Impaired Muscle Force Transmission
  biological_scale: TISSUE
  cell_types:
  - preferred_term: skeletal muscle fiber
    term:
      id: CL:0008002
      label: skeletal muscle fiber
  description: >
    A Col12a1-null mouse model shows decreased grip strength, a delay in
    muscle fiber-type transition, and a deficiency in passive force
    generation, indicating that the matrix-based passive force-transducing
    elastic element normally provided by collagen XII is disrupted.
  evidence:
  - reference: PMID:24334604
    reference_title: "Recessive and dominant mutations in COL12A1 cause a novel EDS/myopathy overlap syndrome in humans and mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "A mouse model with inactivation of the Col12a1 gene showed decreased grip strength, a delay in fiber-type transition and a deficiency in passive force generation while the muscle seems more resistant to eccentric contraction induced force drop, indicating a role for a matrix-based passive force-transducing elastic element in the generation of the weakness."
    explanation: Directly demonstrates the mechanistic link between collagen XII loss and impaired muscle force generation in a Col12a1-null mouse model.
  downstream:
  - target: Proximal and Axial Muscle Weakness
  - target: Congenital Hypotonia
  - target: Skeletal Muscle Atrophy
    description: Chronic impaired force generation and disuse lead to secondary skeletal muscle atrophy, characteristically of the rectus femoris.
  - target: Motor Delay
    description: Impaired force generation delays acquisition of gross motor milestones.
  - target: Kyphoscoliosis
    description: Weakness of paraspinal musculature contributes to progressive spinal curvature.
- name: Joint and Skin Connective Tissue Laxity
  biological_scale: TISSUE
  description: >
    Destabilized joint capsule connective tissue produces distal joint
    hypermobility and, in the severe biallelic form, congenital joint
    contractures and arthrogryposis reflecting a mixed laxity/contracture
    phenotype.
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Distal joint laxity was noted in all patients (Fig. 1A–C), typically affecting wrists and ankles. Concurrent joint contractures were present in six patients and typically affected the long finger flexors"
    explanation: Documents the combined joint-laxity-plus-contracture pattern characteristic of the severe biallelic phenotype.
  downstream:
  - target: Distal Joint Hypermobility
  - target: Arthrogryposis
  - target: Hip Dysplasia
    description: Congenital joint laxity/instability predisposes to hip dysplasia.
  - target: Talipes Equinovarus
    description: Congenital joint contracture affecting the ankle/foot produces talipes equinovarus.
- name: Cardiac Valve Connective Tissue Involvement
  biological_scale: TISSUE
  locations:
  - preferred_term: cardiac valve
    term:
      id: UBERON:0000946
      label: cardiac valve
  description: >
    Destabilized valve leaflet connective tissue produces mild valvular
    anomalies including leaflet thickening, dysplasia, and regurgitation,
    reported in a subset of the severe biallelic cohort.
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Four patients also had evidence of cardiac involvement, with one (F2P2) presenting with Wolff–Parkinson–White syndrome."
    explanation: Documents cardiac involvement, including valvular anomalies, in a subset of the severe biallelic cohort.
  downstream:
  - target: Mitral Regurgitation
- name: Craniofacial and Dysmorphic Features
  biological_scale: TISSUE
  description: >
    Dysmorphic craniofacial findings, evident in all patients of the severe
    biallelic cohort, recur alongside the core connective-tissue/muscle
    phenotype. The specific mechanistic link between the collagen XII/ECM
    defect and these findings is not established in the cited source.
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Dysmorphic features were evident in all patients."
    explanation: Establishes dysmorphic craniofacial features as a consistent finding in the severe biallelic cohort.
  downstream:
  - target: Micrognathia
  - target: Gingival Overgrowth
phenotypes:
- name: Proximal and Axial Muscle Weakness
  phenotype_term:
    preferred_term: Proximal muscle weakness
    term:
      id: HP:0003701
      label: Proximal muscle weakness
  evidence:
  - reference: PMID:40508193
    reference_title: "Myopathic Ehlers-Danlos Syndrome (mEDS) Related to COL12A1: Two Novel Families and Literature Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "present a combination of joint hypermobility and axial, distal, and proximal weakness"
    explanation: Documents combined axial, distal, and proximal muscle weakness as the core myopathic phenotype of mEDS.
- name: Skeletal Muscle Atrophy
  phenotype_term:
    preferred_term: Skeletal muscle atrophy
    term:
      id: HP:0003202
      label: Skeletal muscle atrophy
  evidence:
  - reference: PMID:40508193
    reference_title: "Myopathic Ehlers-Danlos Syndrome (mEDS) Related to COL12A1: Two Novel Families and Literature Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "confirming the characteristic atrophy of the rectus femoris"
    explanation: Documents rectus femoris muscle atrophy as a characteristic imaging finding in mEDS.
- name: Congenital Hypotonia
  subtype: mEDS Recessive
  phenotype_term:
    preferred_term: Hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All patients presented with congenital onset symptoms including reduced fetal movement, hypotonia, and hip dysplasia"
    explanation: Documents congenital hypotonia as a core presenting feature of the severe biallelic phenotype.
- name: Distal Joint Hypermobility
  subtype: mEDS Recessive
  phenotype_term:
    preferred_term: Distal joint hypermobility
    term:
      id: HP:0020152
      label: Distal joint hypermobility
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Distal joint laxity was noted in all patients (Fig. 1A–C), typically affecting wrists and ankles."
    explanation: Documents distal joint hypermobility/laxity in all patients of the biallelic cohort.
- name: Arthrogryposis
  subtype: mEDS Recessive
  phenotype_term:
    preferred_term: Arthrogryposis multiplex congenita
    term:
      id: HP:0002804
      label: Arthrogryposis multiplex congenita
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "four patients (F1P1, F2P2, F3P3 and F4P4) presenting with arthrogryposis"
    explanation: Documents arthrogryposis in a subset of the severe biallelic cohort.
- name: Hip Dysplasia
  subtype: mEDS Recessive
  phenotype_term:
    preferred_term: Hip dysplasia
    term:
      id: HP:0001385
      label: Hip dysplasia
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All patients presented with congenital onset symptoms including reduced fetal movement, hypotonia, and hip dysplasia"
    explanation: Documents congenital hip dysplasia as a core presenting feature of the severe biallelic phenotype.
- name: Gingival Overgrowth
  subtype: mEDS Recessive
  phenotype_term:
    preferred_term: Gingival hypertrophy
    term:
      id: HP:0000212
      label: Gingival overgrowth
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other common findings included micrognathia (n = 4), gingival hypertrophy (n = 6)"
    explanation: Documents gingival hypertrophy in 6 of 8 patients in the severe biallelic cohort, a dysmorphic feature distinguishing mEDS from typical EDS subtypes.
- name: Micrognathia
  subtype: mEDS Recessive
  phenotype_term:
    preferred_term: Micrognathia
    term:
      id: HP:0000347
      label: Micrognathia
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Other common findings included micrognathia (n = 4), gingival hypertrophy (n = 6)"
    explanation: Documents micrognathia in 4 of 8 patients in the severe biallelic cohort.
- name: Mitral Regurgitation
  subtype: mEDS Recessive
  phenotype_term:
    preferred_term: Mitral regurgitation
    term:
      id: HP:0001653
      label: Mitral regurgitation
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "F1P1 and F3P3 had echocardiograms in infancy showing mild valvular anomalies with thickened mitral valve leaflets and mild-to-moderate mitral regurgitation in F1P1 and dysplastic mitral and tricuspid valves with redundant tissue and mild mitral valve regurgitation in F3P3"
    explanation: Documents mitral regurgitation with valve dysplasia in two patients of the severe biallelic cohort. (Note -- a third patient, F2P2, is separately tabulated with "MVP" i.e. true mitral valve prolapse, per Table 1's legend; that is a distinct finding not evidenced by this quote, so this phenotype is scoped to the regurgitation/dysplasia finding the quote actually supports.)
- name: Talipes Equinovarus
  subtype: mEDS Recessive
  phenotype_term:
    preferred_term: Talipes equinovarus
    term:
      id: HP:0001762
      label: Talipes equinovarus
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Congenital hip dysplasia Talipes equinovarus"
    explanation: Listed as a presenting congenital orthopedic finding (alongside hip dysplasia) in one patient of the severe biallelic cohort.
- name: Kyphoscoliosis
  subtype: mEDS Recessive
  phenotype_term:
    preferred_term: Kyphoscoliosis
    term:
      id: HP:0002751
      label: Kyphoscoliosis
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "F1P1 and F3P3 were noted to have progressive thoracic kyphoscoliosis"
    explanation: Documents progressive kyphoscoliosis as a musculoskeletal complication in the biallelic cohort.
- name: Motor Delay
  subtype: mEDS Recessive
  phenotype_term:
    preferred_term: Motor delay
    term:
      id: HP:0001270
      label: Motor delay
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All patients had delayed acquisition of motor milestones."
    explanation: Documents delayed motor milestone acquisition across the biallelic cohort.
diagnosis:
- name: Molecular Genetic Testing
  description: Diagnosis is established by identifying a heterozygous (dominant) or biallelic (recessive) pathogenic COL12A1 variant in an individual with suggestive combined muscle/connective-tissue clinical findings.
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Next-generation-based sequencing identified rare biallelic COL12A1 (NM_004370.6) variants in all eight patients."
    explanation: Describes the molecular diagnostic approach used to confirm biallelic COL12A1-related disease.
- name: Dermal Fibroblast Immunostaining
  description: Immunocytochemistry of patient-derived dermal fibroblasts for collagen XII expression can support a diagnosis and correlates with clinical severity, ranging from complete absence in severe disease to mild reduction in milder disease.
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "in vitro immunocytochemistry analysis in fibroblasts ranged from complete absence of Collagen XII expression in a patient with severe disease, to a mild reduction in a patient with milder disease"
    explanation: Describes dermal fibroblast immunostaining as a supportive diagnostic tool correlating with disease severity.
treatments:
- name: Orthopedic Management of Scoliosis and Joint Contractures
  description: >
    Orthopedic surveillance and surgical correction of progressive
    kyphoscoliosis and joint contractures, most often required in the more
    severe mEDS Recessive phenotype.
  treatment_term:
    preferred_term: Orthopedic Surgical Procedure
    term:
      id: NCIT:C16186
      label: Orthopedic Surgical Procedure
  therapeutic_modality: SURGERY
  target_mechanisms:
  - target: Kyphoscoliosis
    treatment_effect: MODULATES
    description: >
      Surgical instrumentation mechanically stabilizes and corrects the
      progressive spinal curvature; it addresses the structural consequence
      of muscle weakness and connective-tissue laxity rather than the
      underlying collagen XII defect.
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "F2P2, F6P7 and F7P8 had progressive scoliosis requiring spinal surgery at age 10 years in F2P2."
    explanation: Documents spinal surgery for progressive scoliosis in the biallelic (mEDS Recessive) cohort.
- name: Respiratory Support (Noninvasive to Invasive Mechanical Ventilation)
  description: >
    Escalating respiratory support ranging from noninvasive ventilation to
    tracheostomy and ventilator dependency, reflecting the variable severity
    of respiratory muscle involvement across the mEDS spectrum.
  treatment_term:
    preferred_term: Mechanical Ventilation
    term:
      id: NCIT:C70909
      label: Mechanical Ventilation
  therapeutic_modality: DEVICE
  target_mechanisms:
  - target: Proximal and Axial Muscle Weakness
    treatment_effect: MODULATES
    description: >
      Supports ventilation when respiratory muscle weakness becomes severe
      enough to compromise breathing; it does not correct the underlying
      muscle force-transmission defect.
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Respiratory involvement was variable, ranging from none to tracheostomy and ventilatory dependency since birth (F6P7)."
    explanation: Documents the range of respiratory support required in the biallelic (mEDS Recessive) cohort, from none to lifelong ventilator dependency.
  - reference: PMID:40508193
    reference_title: "Myopathic Ehlers-Danlos Syndrome (mEDS) Related to COL12A1: Two Novel Families and Literature Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Three out of 10 UCMD2 patients began non-invasive ventilation (NIV) before the age of 3"
    explanation: Documents early noninvasive ventilation initiation in a subset of UCMD2 (mEDS Recessive) patients, drawn from a systematic literature review.
- name: Nutritional Support (Nasogastric or Gastrostomy Feeding)
  description: >
    Enteral feeding support for neonatal feeding difficulties arising from
    congenital hypotonia and weakness, common in the severe mEDS Recessive
    phenotype.
  treatment_term:
    preferred_term: Nutritional Support
    term:
      id: NCIT:C15433
      label: Nutritional Support
  therapeutic_modality: OTHER
  target_mechanisms:
  - target: Congenital Hypotonia
    treatment_effect: MODULATES
    description: >
      Provides enteral nutrition when hypotonia-related feeding difficulty
      makes oral intake unsafe or insufficient; it does not correct the
      underlying hypotonia itself.
  evidence:
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neonatal feeding difficulties were present in seven, requiring a nasogastric or gastrostomy tube placement."
    explanation: Documents enteral feeding support for neonatal feeding difficulty in the biallelic (mEDS Recessive) cohort.
- name: Genetic Counseling
  description: >
    Genetic counseling regarding the dominant (typically de novo) or
    recessive (biallelic) inheritance pattern, recurrence risk, and
    availability of carrier and prenatal/preimplantation testing.
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:24334604
    reference_title: "Recessive and dominant mutations in COL12A1 cause a novel EDS/myopathy overlap syndrome in humans and mice."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a de novo dominant mutation in collagen XII (COL12A1) as underlying a novel overlap syndrome involving muscle and connective tissue"
    explanation: Documents the typically de novo dominant inheritance relevant to counseling for mEDS Dominant.
  - reference: PMID:39923201
    reference_title: "Clinical characterization of Collagen XII-related disease caused by biallelic COL12A1 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Next-generation-based sequencing identified rare biallelic COL12A1 (NM_004370.6) variants in all eight patients."
    explanation: Documents the biallelic recessive inheritance relevant to counseling for mEDS Recessive, including carrier-testing implications for relatives.

📚

References & Deep Research

References

2

PMID:24334604

Recessive and dominant mutations in COL12A1 cause a novel EDS/myopathy overlap syndrome in humans and mice.

No top-level findings curated for this source.

PMID:28306229

The 2017 international classification of the Ehlers-Danlos syndromes.

No top-level findings curated for this source.

Deep Research

1

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

Evaluations and curation notes (3)

Add treatments section (round-5 review fix) · 2026-09-18T02:33:15Z · View source

Added the treatments: section the round-5 PR review flagged as missing -- Myopathic EDS was the only one of the six entries in this PR with none. Four treatments, all cited to primary literature already in the file's evidence base (no new deep-research pass needed; the DR report's own Treatment section synthesized citation keys that could not be reliably resolved to PMIDs, so real quotes were sourced directly from the two already-cited clinical characterization papers instead): (1) Orthopedic Management of Scoliosis and Joint Contractures (NCIT:C16186, target_mechanisms -> Kyphoscoliosis), citing PMID:39923201's report of spinal surgery at age 10 in the biallelic cohort; (2) Respiratory Support / Mechanical Ventilation (NCIT:C70909, target_mechanisms -> Proximal and Axial Muscle Weakness), citing both PMID:39923201 (tracheostomy/ventilator dependency range) and PMID:40508193 (early NIV in UCMD2 patients); (3) Nutritional Support via nasogastric/gastrostomy feeding (NCIT:C15433, target_mechanisms -> Congenital Hypotonia), citing PMID:39923201's report of feeding difficulties in 7 of the biallelic cohort; (4) Genetic Counseling (NCIT:C15240, no target_mechanisms per established KB precedent), reusing the already-verified dominant/recessive inheritance evidence. One snippet initially failed reference validation because it retained the source paper's inline citation bracket markers ([17,31], [37,38]); trimmed to the substantive sentence and re-verified. This addresses one of three items bundled into a single push per round-5 review feedback on PR #11899, alongside a Periodontal EDS full-text reference fetch (unrelated file) and a missing NCIT term-cache row for Dermatosparaxis EDS (unrelated file, previously reverted in error as out-of-scope churn from an earlier merge-conflict cleanup, now confirmed legitimate and restored). Validated: just validate-disorders (batched with Periodontal and Dermatosparaxis, 138/138 snippets verified), check-causal-targets, check-entity-refs, check-qualifier-terms, check-duplicate-keys, check-enum-values, check-genereviews.

Self-review fixes + deep-research cross-check: Myopathic Ehlers-Danlos Syndrome · 2026-09-16T18:07:46Z · View source

Ran the falcon deep-research pass required by the task template (already launched before the CREATE commit; completed in the background, 17/17 references resolved/0 confabulated). Unresolved/obsolete terms it flagged (HP:0002802, HP:0002355, GO:0062023) and the harmless MONDO:0034022 template-placeholder label mismatch are all pre-existing report artifacts this entry never bound. Cross-checked the report's phenotype comparison table against the entry: strongly corroborates the dominant/recessive split and all 12 curated phenotypes, and surfaces one plausible addition (pes planus in dominant disease, sourced to a paper not yet fetched) that was not added given time budget. Separately, spawned a fresh general-purpose subagent loaded with the dismech-pr-review skill to red-team the entry before the DR cross-check landed. It found two BLOCKING issues and several SUGGESTED ones, addressed here: (1) 8 of 12 phenotypes (Skeletal Muscle Atrophy, Hip Dysplasia, Gingival Overgrowth, Micrognathia, Mitral Valve Prolapse [since renamed], Talipes Equinovarus, Kyphoscoliosis, Motor Delay) had no downstream edge from any pathophysiology node, directly contradicting the CREATE history record's claim that all phenotypes were wired into the graph -- just check-causal-targets did not catch this because it only checks for dangling targets, not zero-indegree phenotype nodes. Fixed by adding new downstream edges from the existing muscle-weakness and joint-laxity nodes (Skeletal Muscle Atrophy, Motor Delay, Kyphoscoliosis from Impaired Muscle Force Transmission; Hip Dysplasia, Talipes Equinovarus from Joint and Skin Connective Tissue Laxity) and by adding two new pathophysiology nodes: 'Cardiac Valve Connective Tissue Involvement' (targeting the renamed Mitral Regurgitation phenotype) and 'Craniofacial and Dysmorphic Features' (targeting Micrognathia and Gingival Overgrowth, with an explicit hedge in its description that the mechanistic link to the collagen XII/ECM defect is not established in the cited source -- an honest disconnect-flagged edge rather than a fabricated causal claim). (2) The 'Mitral Valve Prolapse'/HP:0001634 phenotype's snippet actually described valve dysplasia and regurgitation in patients F1P1/F3P3, not prolapse; the source's Table 1 legend shows true MVP was recorded only for a different patient (F2P2, alongside HCM/WPW). Renamed the phenotype to 'Mitral Regurgitation'/HP:0001653, which the existing snippet does support, and added a parenthetical note in the explanation distinguishing it from the F2P2 MVP finding this entry does not separately evidence. Also addressed three SUGGESTED findings: added subtype: mEDS Recessive to Distal Joint Hypermobility, Kyphoscoliosis, and Motor Delay for consistency with five sibling phenotypes already tagged from the same 100%-biallelic-cohort source (PMID:39923201); added a notes: caveat on the COL12A1 Biallelic Loss-of-Function pathophysiology node that zygosity: HOMOZYGOUS (single-valued slot) undercounts a cohort that is actually a mix of homozygous and compound heterozygous genotypes; and softened the top-level description's claim about a 'shared downstream node' with classical-like EDS (TNXB) to state it is a mechanistic parallel (both disorders converge on decorin/tenascin-X depletion) rather than an implied structural link between the two dismech entries, since no conforms_to or module connects them. Did NOT act on the fourth SUGGESTED finding: whether the 'mEDS Recessive' subtype should exist at all given a pre-existing, independently-anchored thin 'UCMD2' has_subtypes stub on the same MONDO:0014654 inside kb/disorders/Ullrich_Congenital_Muscular_Dystrophy.yaml (discovered and cross-referenced in the CREATE commit). The reviewer recommended escalating this lump/split question to human review rather than treating the two-way notes cross-reference as sufficient; agreed this is the right call, and it is recorded here rather than resolved unilaterally by restructuring either entry into a Grouping. Revalidated with: just validate (27/27 snippets verified, up from 25), just validate-disorders (CI-authoritative gate, passed), just check-causal-targets (0 new dangling targets), just check-entity-refs, just check-duplicate-keys, just check-enum-values, and a manual PyYAML check confirming zero orphaned phenotype nodes remain (was 8/12 before this pass).

Create: Myopathic Ehlers-Danlos Syndrome · 2026-09-16T17:54:13Z · View source

Created new entry for myopathic Ehlers-Danlos syndrome (mEDS), a connective-tissue/muscle overlap disorder caused by COL12A1 (collagen XII) variants. Modeled as a single genotype-correlated severity spectrum with two subtypes rather than two diseases: mEDS Dominant (heterozygous, milder, anchors the disease_term via MONDO:0034022 'Bethlem myopathy 2', an exact MONDO synonym of 'myopathic EDS'/'EDS, myopathic type') and mEDS Recessive (biallelic loss-of-function, more severe, MONDO:0014654 'Ullrich congenital muscular dystrophy 2'). MONDO has no separate EDS-branded top-level term for this disease -- confirmed via runoak relationship search on the COL12A1 HGNC id (RO:0004003) rather than a label search on 'myopathic Ehlers-Danlos', which returns nothing. No GeneReviews chapter exists for myopathic EDS, COL12A1, Bethlem myopathy, or Ullrich congenital muscular dystrophy (searched PubMed genereviews[book] for each; no hits), recorded in notes:. Sources: the founding 2014 discovery paper (PMID:24334604, Zou et al., recessive+dominant mutations in mouse and human), a 2020 cohort-expansion mechanism paper demonstrating that COL12A1 variants secondarily deplete extracellular decorin AND tenascin-X (PMID:31273343, full text -- mechanistically linking this entry to classical-like EDS/TNXB at a shared downstream ECM node), a 2025 clinical characterization of the severe biallelic end (PMID:39923201, full text, 8 patients/7 families), and a 2025 review with two novel dominant families (PMID:40508193). Pathograph converges dominant (DOMINANT_NEGATIVE, subunit-interface variants) and recessive (LOSS_OF_FUNCTION, biallelic) molecular nodes on a shared 'Depleted Collagen XII-Bridged Extracellular Matrix' node, branching into a muscle-force-transmission arm (citing a Col12a1-null mouse model's decreased grip strength and passive-force-generation deficiency) and a joint/skin-laxity arm; all phenotypes wired into the causal graph. Ran just discover-datasets Myopathic_Ehlers-Danlos_Syndrome: both candidates that came back (geo:GSE20025, geo:GSE103270) were Named Entity Confusion -- fetched and confirmed both are COL6A1/2/3-related classic collagen-VI Bethlem myopathy studies, not COL12A1/MONDO:0034022 'Bethlem myopathy 2' -- so no datasets: block was added. Validated with: just validate (25/25 snippets verified after fixing one non-propositional 2-word table-cell snippet flagged by the whole-KB just check-snippet-length gate), just validate-disorders (CI-authoritative gate, passed), just check-causal-targets (0 new dangling targets), just check-entity-refs, just check-duplicate-keys, just check-enum-values, just check-qualifier-terms, and just list-gene-term-mismatches (0/5 mismatches). just compliance: 89.4% global / 90.2% weighted. A falcon deep-research pass (just dr_fallback='--fallback' research-disorder falcon Myopathic_Ehlers-Danlos_Syndrome) was launched for cross-check per the default-provider instruction; its findings, if any, will be recorded in a follow-up EDIT history record. Discovered a real cross-file overlap while checking the cache diff for the PMID:24334604 fetch: it was already tracked, cited by an existing kb/disorders/Ullrich_Congenital_Muscular_Dystrophy.yaml entry's thin 'UCMD2' has_subtypes stub (also anchored on MONDO:0014654, one description line plus two evidence items). This is not accidental duplication -- that entry frames UCMD as a neuromuscular-disease syndrome with COL6A1/2/3 as the primary cause and COL12A1 as a rare phenocopy subtype, while this new entry frames the same COL12A1 gene-disease relationship through the 2017 international EDS classification's named 'myopathic EDS' subtype, and additionally covers the milder dominant end (Bethlem myopathy 2) that the Ullrich-framed entry does not model at all. Added a two-way cross-reference rather than duplicating or deleting either curation: a notes: paragraph in this entry pointing to the existing UCMD2 stub and explaining the dual classification, and a matching one-paragraph addition to that file's UCMD2 subtype description pointing back here. Both files revalidated together with just validate-disorders (110/110 snippets verified across both).

Falcon ▸

Myopathic Ehlers–Danlos Syndrome (mEDS): Disease-Characteristics Report

Edison Scientific Literature 41 citations 2026-09-16T18:01:27.816552

Myopathic Ehlers–Danlos Syndrome (mEDS): Disease-Characteristics Report

Target: Myopathic Ehlers–Danlos syndrome / COL12A1-related myopathy
Category: Mendelian extracellular-matrix disorder
Knowledge cut-off emphasized: 2024, with a clearly labeled 2025 cohort included because it materially changes the recessive natural-history evidence.

Executive summary

Myopathic Ehlers–Danlos syndrome is an exceptionally rare, usually congenital disorder caused by germline pathogenic variants in COL12A1, combining congenital myopathy with connective-tissue manifestations. The characteristic pattern is congenital hypotonia and muscle weakness, delayed motor development, distal joint hypermobility, proximal or large-joint contractures, spinal deformity, and variably soft skin, atrophic scars, or impaired wound healing. Dominant-negative glycine substitutions and in-frame exon-skipping alleles usually cause milder, ambulant disease, sometimes evolving into adult distal myopathy. Biallelic loss-of-function generally causes a more severe congenital phenotype, although independent ambulation and improvement over time are possible. The primary lesion is defective collagen XII organization around collagen-I fibrils, disrupting extracellular-matrix architecture, mechanics, cell–cell organization, and force transmission rather than the muscle contractile apparatus itself. (delbaere2020noveldefectsin pages 2-3, zou2014recessiveanddominant pages 1-2, mohassel2019dominantcollagenxii pages 2-3, mccarty2025clinicalcharacterizationof pages 7-9)

The 2023 authoritative review states: “Mutations in the collagen XII gene cause myopathic Ehlers-Danlos syndrome (mEDS), an early-onset disease characterized by overlapping connective tissue abnormalities and muscle weakness.” It further describes delayed motor development, weakness, laxity, hypermobility, contractures, and abnormal wound healing. (izu2023collagenxiimediated pages 1-2)

1. Disease information

Definition and nomenclature

mEDS is one of the monogenic EDS types recognized in the 2017 international classification. It is also described as COL12A1-related myopathy, COL12A1-related myopathic EDS, EDS/myopathy overlap syndrome, collagen XII–related disease, Bethlem myopathy 2/Bethlem-like myopathy, and, for severe recessive presentations, Ullrich congenital muscular dystrophy 2/UCMD2-like disease. The terminology reflects a continuous collagen-XII disease spectrum rather than proven discrete biological entities. (delbaere2020noveldefectsin pages 2-3, merlini2025myopathicehlersdanlossyndrome pages 7-9, merlini2025myopathicehlersdanlossyndrome pages 1-2)

Identifiers

MONDO:0034022: Open Targets currently labels this entity Bethlem myopathy 2 and associates it with COL12A1/ENSG00000111799. Thus, the supplied MONDO identifier is available, but its preferred label is not exactly “myopathic EDS.” (OpenTargets Search: myopathic Ehlers-Danlos syndrome-COL12A1)
OMIM: COL12A1-related dominant and recessive phenotypes are commonly indexed under Bethlem myopathy 2 and Ullrich congenital muscular dystrophy 2, respectively; a single unambiguous mEDS-only OMIM identifier was not established in the retrieved evidence.
Orphanet: mEDS is recognized as an ultra-rare EDS subtype, but a disease-specific ORPHA number was not verified from the retrieved primary evidence.
ICD-10/ICD-11 and MeSH: no validated mEDS-specific code or descriptor was identified. Implementations generally require an umbrella EDS/heritable connective-tissue-disorder code plus molecular annotation.
Gene: COL12A1, collagen type XII alpha-1 chain; Ensembl ENSG00000111799. (OpenTargets Search: myopathic Ehlers-Danlos syndrome-COL12A1)

This report represents aggregated disease-level evidence from published patients, families, fibroblast assays, and animal models—not individual EHR-derived data.

2. Etiology

Causal factor

The cause is a germline pathogenic COL12A1 variant. Collagen XII is a homotrimeric fibril-associated collagen with interrupted triple helices (FACIT) that organizes collagen-I-rich extracellular matrices. Both autosomal-dominant and autosomal-recessive disease occur. (izu2023collagenxiimediated pages 1-2, chiquet2014collagenxiiprotecting pages 1-3, delbaere2020noveldefectsin pages 1-2)

Genetic risk

Dominant disease: usually heterozygous glycine substitutions in the triple-helical region or in-frame exon-skipping alleles. These interfere with secretion or assembly of homotrimeric collagen XII and act predominantly through dominant-negative effects. (punetha2017novelcol12a1variant pages 3-4, mohassel2019dominantcollagenxii pages 2-3, mccarty2025clinicalcharacterizationof pages 2-3)
Recessive disease: biallelic loss-of-function or severely hypomorphic alleles cause marked reduction or absence of collagen XII. (mccarty2025clinicalcharacterizationof pages 1-2)
The first discovery study included two severely affected siblings with homozygous loss of function and one milder patient with a de novo dominant missense variant. (zou2014recessiveanddominant pages 1-2)

Variants supported in retrieved primary reports include c.8329G>C (p.Gly2777Arg), absent from ExAC and NHLBI ESP in the 2017 report; heterozygous exon-skipping defects designated Δ52, Δ53, Δ54, and Δ56; and biallelic p.Ile1393Phefs*11/p.Ala1110Asp in one family. A 2024 report identified homozygous c.8903C>T (p.Pro2968Leu) but treated its disease classification cautiously because functional and segregation evidence remained limited. (delbaere2020noveldefectsin pages 1-2, punetha2017novelcol12a1variant pages 3-4, ipek2024col12a1genevariant pages 5-6, mccarty2025clinicalcharacterizationof pages 1-2)

All established mEDS alleles are germline. Somatic COL12A1 variants reported in cancers do not establish mEDS.

Non-genetic, protective, and gene–environment factors

No environmental toxin, infection, lifestyle exposure, susceptibility locus, protective allele, modifier gene, or validated gene–environment interaction has been demonstrated to cause or prevent mEDS. Mechanical loading regulates normal collagen-XII expression—tensile/cyclic strain induces it in fibroblastic cells—but this is mechanobiology, not evidence that exercise or occupation causes Mendelian disease. (izu2023collagenxiimediated pages 1-2, chiquet2014collagenxiiprotecting pages 3-4)

Family history increases prior probability in inherited cases but may be absent with de novo dominant variants. Consanguinity can increase the probability of recessive disease; no quantified attributable risk or established founder allele was found.

3. Phenotypes

The core genotype–phenotype distinction is summarized below.

Domain	Autosomal-dominant COL12A1 disease	Autosomal-recessive/biallelic COL12A1 disease	Ontology suggestions
Onset	Usually congenital or childhood hypotonia/motor delay; adolescent presentation and symptomatic distal weakness beginning in the fourth decade also occur. (mohassel2019dominantcollagenxii pages 2-3, merlini2025myopathicehlersdanlossyndrome pages 2-3)	Congenital onset; reduced fetal movement, hypotonia, hip dysplasia, and delayed milestones occurred in all eight individuals in the 2025 cohort; arthrogryposis occurred in 4/8. (mccarty2025clinicalcharacterizationof pages 2-3)	HP:0002808 Abnormal fetal movements; HP:0001252 Hypotonia; HP:0001263 Global developmental delay; HP:0002751 Kyphosis
Severity and course	Generally mild, with retained ambulation and slowly progressive weakness; childhood function may be relatively preserved before adult distal weakness. Rare severe neonatal respiratory presentations occur. (mohassel2019dominantcollagenxii pages 2-3, merlini2025myopathicehlersdanlossyndrome pages 7-9)	Variable but usually more severe: 5/8 had profound congenital weakness, minimal milestones, respiratory insufficiency, and feeding difficulty; 3/8 had mild-to-moderate weakness and walked independently. Motor ability often improved slowly without regression. (mccarty2025clinicalcharacterizationof pages 7-9, mccarty2025clinicalcharacterizationof pages 2-3)	HP:0003701 Proximal muscle weakness; HP:0002460 Distal muscle weakness; HP:0002376 Developmental regression—typically absent
Motor function and weakness	Axial, proximal, or distal weakness; adult disease may selectively involve anterior lower-leg muscles, finger extensors, and intrinsic hand muscles. In a later review, 31/33 reported dominant cases remained ambulant. (mohassel2019dominantcollagenxii pages 2-3, merlini2025myopathicehlersdanlossyndrome pages 7-9)	Proximal and distal lower-limb weakness ranging from isolated hip-flexor weakness to profound generalized weakness. Five of 15 literature cases never walked; some ambulant children walked at 15 months, 16 months, or 3 years. (mccarty2025clinicalcharacterizationof pages 2-3, merlini2025myopathicehlersdanlossyndrome pages 7-9)	HP:0003324 Generalized muscle weakness; HP:0008948 Pelvic-girdle muscle weakness; HP:0009055 Distal lower-limb muscle weakness; HP:0002355 Difficulty walking
Joints and spine	Joint hyperlaxity in 5/6 patients in a 2019 series; pes planus common, with occasional ankle contractures. Distal hypermobility may coexist with proximal contractures; kyphoscoliosis can progress. (punetha2017novelcol12a1variant pages 3-4, mohassel2019dominantcollagenxii pages 2-3)	Distal laxity in all eight recent patients; contractures in 6/8, often involving finger flexors and knees. Progressive scoliosis requiring surgery occurred in 3/8 and thoracic kyphoscoliosis in 2/8. (mccarty2025clinicalcharacterizationof pages 2-3)	HP:0001382 Joint hypermobility; HP:0001371 Flexion contracture; HP:0001763 Pes planus; HP:0002650 Scoliosis; HP:0002751 Kyphosis; HP:0002802 Arthrogryposis multiplex congenita
Skin, wound healing, and craniofacial findings	Soft/doughy skin, atrophic scarring, abnormal wound healing, and high-arched palate have been reported; reliable frequencies are unavailable. (delbaere2020noveldefectsin pages 2-3, punetha2017novelcol12a1variant pages 3-4, izu2023collagenxiimediated pages 1-2)	Dysmorphic features were universal in the recent cohort; gingival hypertrophy occurred in 6/8, with micrognathia and dental abnormalities also reported. Velvety palms/soles occurred, whereas keloid scarring was absent; skin-feature frequencies otherwise unavailable. (mccarty2025clinicalcharacterizationof pages 7-9, mccarty2025clinicalcharacterizationof pages 2-3)	HP:0000974 Hyperextensible skin; HP:0001075 Atrophic scars; HP:0000278 Retrognathia; HP:0000212 Gingival overgrowth; HP:0000164 Abnormality of the dentition; HP:0000218 High-arched palate
Respiratory, feeding, and cardiac involvement	No cardiac or pulmonary disease was detected in the six-patient 2019 series; reported FVC values in later compiled cases ranged approximately 58–115% predicted. Rare severe dominant neonatal respiratory failure is reported. Feeding frequencies unavailable. (mohassel2019dominantcollagenxii pages 2-3, merlini2025myopathicehlersdanlossyndrome pages 7-9, merlini2025myopathicehlersdanlossyndrome pages 2-3)	Seven of eight required nasogastric or gastrostomy feeding. Respiratory involvement ranged from absent to ventilator dependence from birth; cardiac findings occurred in 4/8. Exact lesion-specific frequencies are unavailable. (mccarty2025clinicalcharacterizationof pages 2-3)	HP:0002093 Respiratory insufficiency; HP:0002020 Gastroesophageal reflux; HP:0008872 Feeding difficulties in infancy; HP:0011968 Feeding by nasogastric tube; HP:0011471 Gastrostomy tube feeding; HP:0001627 Abnormal heart morphology
Laboratory and electrophysiology	CK is usually normal or mildly elevated, although compiled values ranged from about 42–1,310 U/L. One congenital case had normal CK, EMG, and nerve-conduction studies. (punetha2017novelcol12a1variant pages 3-4, merlini2025myopathicehlersdanlossyndrome pages 2-3)	CK was normal in four and mildly elevated in two reported patients. EMG/nerve-conduction evidence was unavailable in the extracted cohort. (mccarty2025clinicalcharacterizationof pages 2-3)	HP:0003236 Elevated serum creatine kinase; HP:0003458 EMG abnormality—variable/not established
Biopsy and imaging	Muscle biopsy may show mild, nonspecific, non-dystrophic myopathy with fiber-size variation and increased connective tissue. Imaging can demonstrate rectus-femoris, posterior-thigh, neck, and lumbar muscle involvement. (punetha2017novelcol12a1variant pages 3-4, merlini2025myopathicehlersdanlossyndrome pages 7-9, merlini2025myopathicehlersdanlossyndrome pages 1-2)	Four biopsies showed mild myopathic changes without dystrophic necrosis/regeneration. MRI ranged from normal to severe diffuse atrophy and fatty replacement; posterior-thigh and rectus-femoris involvement may be selective. (mccarty2025clinicalcharacterizationof pages 7-9, mccarty2025clinicalcharacterizationof pages 3-4)	HP:0003199 Decreased muscle mass; HP:0003712 Abnormal muscle fiber morphology; HP:0003808 Abnormal muscle biopsy finding; UBERON:0001383 skeletal muscle tissue
Molecular mechanism	Glycine substitutions and in-frame exon-skipping variants affecting the triple-helical region typically exert dominant-negative effects, causing intracellular retention, impaired secretion, or abnormal fibril-associated collagen-XII deposition. Mutant-allele siRNA restored ECM localization in exon-52-deletion fibroblasts. (punetha2017novelcol12a1variant pages 3-4, mohassel2019dominantcollagenxii pages 2-3, mccarty2025clinicalcharacterizationof pages 2-3)	Usually biallelic loss of function, producing markedly reduced or absent collagen XII. Fibroblast collagen-XII abundance correlated with clinical severity in the eight-patient cohort. (mccarty2025clinicalcharacterizationof pages 1-2)	GO:0030198 extracellular matrix organization; GO:0030199 collagen fibril organization; GO:0005201 extracellular matrix structural constituent; GO:0062023 collagen-containing extracellular matrix; CL:0000057 fibroblast
Prognosis and function	Most patients retain ambulation; weakness may remain mild for years but can progress in adulthood. No genotype-specific survival, mortality, or validated quality-of-life statistics are available. (mohassel2019dominantcollagenxii pages 2-3, merlini2025myopathicehlersdanlossyndrome pages 7-9)	Lifelong congenital disease with severity ranging from ventilator-dependent profound disability to independent walking. Improvement without motor regression is documented, but survival rates, life expectancy, and validated quality-of-life outcomes are unavailable. (mccarty2025clinicalcharacterizationof pages 7-9, mccarty2025clinicalcharacterizationof pages 2-3)	HP:0002355 Difficulty walking; HP:0003547 Shoulder-girdle muscle weakness; ICF mobility and self-care domains

Table: Evidence-based comparison of autosomal-dominant and biallelic COL12A1-related myopathic Ehlers-Danlos syndrome across clinical, diagnostic, molecular, and prognostic domains. Frequencies are reported only where available, and evidence gaps are explicitly marked.

Principal phenotype annotations

Congenital hypotonia — HP:0001252; usually neonatal/congenital, variable severity.
Generalized, proximal, axial, or distal weakness — HP:0003324, HP:0003701, HP:0002460; mild and slowly progressive in many dominant cases, profound congenitally in severe recessive disease.
Delayed motor milestones — HP:0001270/HP:0001263; walking may be delayed to early childhood, never achieved in severe cases, or retained into adulthood.
Distal/generalized joint hypermobility — HP:0001382; a major recurring feature and present in 5/6 patients in one dominant series and all eight patients in the recent biallelic cohort. (mohassel2019dominantcollagenxii pages 2-3, mccarty2025clinicalcharacterizationof pages 2-3)
Proximal or large-joint/finger/knee contractures — HP:0001371; present in 6/8 of the recent biallelic cohort. (mccarty2025clinicalcharacterizationof pages 2-3)
Arthrogryposis — HP:0002802; 4/8 in that cohort. (mccarty2025clinicalcharacterizationof pages 2-3)
Scoliosis/kyphoscoliosis — HP:0002650, HP:0002751; may progress and require surgery.
Pes planus — HP:0001763; common in dominant distal-myopathy presentations. (mohassel2019dominantcollagenxii pages 2-3)
Soft/doughy or hyperextensible skin and atrophic scarring — HP:0000974, HP:0001075; frequencies remain poorly quantified. (delbaere2020noveldefectsin pages 2-3)
Gingival hypertrophy and dental abnormalities — HP:0000212, HP:0000164; gingival hypertrophy occurred in 6/8 biallelic patients. (mccarty2025clinicalcharacterizationof pages 2-3)
Feeding difficulty/enteral feeding — HP:0011968, HP:0011471; 7/8 biallelic patients required nasogastric or gastrostomy feeding. (mccarty2025clinicalcharacterizationof pages 2-3)
Respiratory insufficiency — HP:0002093; ranges from absent to neonatal ventilator dependence in biallelic disease; uncommon in typical dominant disease.
Patellar instability — suggested HP:0002999 or a more specific HPO patellar-dislocation term; human imaging and Col12a1-null mice support inclusion. (zhu2021ablationofthe pages 16-20)

Quality of life

No disease-specific EQ-5D, SF-36, PROMIS, or validated patient-reported-outcome study was found. Functional burden plausibly arises from delayed walking, falls, weakness, spinal deformity, feeding or ventilatory dependence, surgery, and mobility-aid requirements, but quantitative quality-of-life effects remain unknown.

4. Genetic and molecular information

Gene and protein

COL12A1 encodes three identical α1(XII) chains that assemble as collagen-XII homotrimers. Each chain contains two short collagenous domains and non-collagenous domains, including a large NC3 region with fibronectin type-III repeats, von Willebrand factor-A modules, and a thrombospondin N-terminal module. Alternative splicing produces large XIIA and smaller XIIB isoforms; mixed XIIA/XIIB trimers can form. The short isoform predominates in many mature tissues, while long collagen XII remains prominent in bone, tendon, and dermis. (chiquet2014collagenxiiprotecting pages 1-3, delbaere2020noveldefectsin pages 1-2, izu2023collagenxiimediated pages 1-2)

Variant classes and consequences

Missense glycine substitutions: disturb the Gly-X-Y triple-helical motif; p.Gly2777Arg caused intracellular retention and reduced deposited matrix, supporting dominant-negative interference. (punetha2017novelcol12a1variant pages 3-4)
Canonical splice/in-frame exon-skipping variants: preserve the reading frame but alter critical extracellular domains; Δ52/53/54/56 alleles caused variant-specific intracellular accumulation, abnormal long-isoform processing, near-absence of short collagen XII, and altered decorin/tenascin-X. (delbaere2020noveldefectsin pages 1-2)
Frameshift/nonsense/canonical loss-of-function variants: generally biallelic and cause absent or markedly reduced collagen XII, with protein abundance broadly tracking severity. (mccarty2025clinicalcharacterizationof pages 1-2)
VUS: p.Arg1863Cys and p.Pro2968Leu illustrate the need not to diagnose mEDS from rarity or computational prediction alone. Functional evidence, segregation, phenotype concordance, and ACMG/AMP assessment are necessary. (delbaere2020noveldefectsin pages 1-2, ipek2024col12a1genevariant pages 5-6)

Exact gnomAD frequencies were not available for every allele. Disease-causing alleles are expected to be absent or extremely rare; the p.Gly2777Arg report documented absence from the then-current ExAC/ESP databases. (punetha2017novelcol12a1variant pages 3-4)

Modifiers, epigenetics, and chromosomal abnormalities

No validated modifier gene, disease-specific methylation signature, histone alteration, recurrent CNV, translocation, inversion, aneuploidy, or germline-mosaicism rate is established. Parental mosaicism should nevertheless be considered when counseling apparently de novo cases.

5. Environmental information

mEDS is not infectious, toxic, nutritional, occupational, or lifestyle-induced. No pathogen or environmental exposure is implicated. Sensible activity modification may reduce secondary joint injury, fatigue, or falls but does not alter the initiating genotype. Smoking, alcohol, diet, pollutants, and radiation have not been shown to modify penetrance.

6. Mechanism and pathophysiology

Ordered causal chain

A pathogenic germline COL12A1 allele leads to production of a structurally abnormal collagen-XII chain or reduced/absent protein.
Dominant glycine/exon-skipping alleles lead to intracellular retention, defective secretion, and incorporation of abnormal chains into homotrimers; biallelic loss-of-function leads to quantitative collagen-XII deficiency. (delbaere2020noveldefectsin pages 1-2, punetha2017novelcol12a1variant pages 3-4, mohassel2019dominantcollagenxii pages 2-3, mccarty2025clinicalcharacterizationof pages 1-2)
Defective collagen XII leads to impaired association with collagen-I fibrils and disturbed interactions with decorin, tenascin-X, fibromodulin, COMP, and potentially collagen VI. (izu2021collagenxiimediated pages 15-19, chiquet2014collagenxiiprotecting pages 9-11, chiquet2014collagenxiiprotecting pages 3-4)
Disrupted molecular bridging leads to abnormal collagen-fibril spacing, assembly, bundling, and pericellular matrix organization. (izu2021collagenxiimediated pages 15-19, izu2023collagenxiimediated pages 1-2, chiquet2014collagenxiiprotecting pages 9-11)
Abnormal ECM architecture leads to altered tissue stiffness, elasticity, passive-force transmission, mechanotransduction, and cell shape/cell–cell communication. The force-transmission interpretation is strongly supported by mouse physiology but remains partly inferred for human muscle. (izu2021collagenxiimediated pages 15-19, izu2023collagenxiimediated pages 1-2, zou2014recessiveanddominant pages 1-2)
In muscle, these defects lead to reduced passive force and grip strength, delayed fiber-type maturation, weakness, hypotonia, and delayed motor development. (zou2014recessiveanddominant pages 1-2)
In tendons, ligaments, joints, bone, skin, and periodontium, the defects lead to laxity and dislocation, contractures from abnormal muscle–tendon development, scoliosis/kyphosis, bone fragility, skin/scar abnormalities, and gingival/dental manifestations. (mccarty2025clinicalcharacterizationof pages 7-9, mccarty2025clinicalcharacterizationof pages 2-3, izu2021collagenxiimediated pages 15-19, zhu2021ablationofthe pages 16-20)
Severe congenital weakness and bulbar/respiratory involvement lead to delayed or absent milestones, feeding-tube dependence, respiratory insufficiency, and major disability in the most severe recessive cases. (mccarty2025clinicalcharacterizationof pages 2-3)

Pathways and processes

The central pathway is extracellular-matrix organization, not a canonical oncogenic signaling cascade. Relevant GO annotations include:

GO:0030198 extracellular matrix organization
GO:0030199 collagen fibril organization
GO:0062023 collagen-containing extracellular matrix
GO:0005201 extracellular matrix structural constituent
collagen trimer and extracellular/pericellular matrix cellular-component terms
connective-tissue development, tendon development, skeletal-system development, cell–matrix adhesion, cell–cell communication, mechanotransduction, and muscle force transmission.

TGF-β1 and mechanical strain induce collagen-XII expression in normal fibroblastic cells, but a disease-driving TGF-β, MAPK, PI3K–AKT, mTOR, Wnt, immune, apoptotic, autophagic, oxidative-stress, or metabolic pathway has not been demonstrated in mEDS. (izu2023collagenxiimediated pages 1-2, chiquet2014collagenxiiprotecting pages 3-4)

Cells and tissues

Candidate Cell Ontology concepts are fibroblast (CL:0000057), tenocyte, osteoblast, osteocyte, skeletal-muscle fiber/myocyte, chondrocyte, and mesenchymal stromal cell. In mice, single-cell analysis identified Col12a1-positive populations including Tnmd+ tenocytes, Myod1+ myoblasts, and Col2a1+ chondrocytes, with altered matrisome expression in the tenocyte population. This is model-organism evidence, not a human single-cell atlas. (zhu2021ablationofthe pages 16-20)

Molecular profiling

Patient-fibroblast immunocytochemistry, RT-PCR, qPCR, and extracellular-matrix staining show variant-specific collagen-XII defects. No validated human blood biomarker, metabolomic/lipidomic signature, epigenomic signature, spatial transcriptomic study, organoid model, or disease-specific CRISPR screen was found. Allele-specific siRNA rescued extracellular collagen-XII localization in exon-52-deletion fibroblasts, constituting proof of mechanism rather than a clinical therapy. (mohassel2019dominantcollagenxii pages 2-3)

7. Anatomical structures affected

Primary structures are the musculoskeletal and connective-tissue systems:

Skeletal muscle—axial, proximal, and distal muscles; rectus femoris and posterior thigh can show selective imaging abnormalities.
Tendon and ligament—including patellar/quadriceps tendon and cruciate ligaments.
Joints—distal joints, hips, knees, ankles, fingers, and patellofemoral articulation.
Spine and bone—scoliosis, kyphosis, malformed patellar groove, and model-supported bone fragility.
Skin and scar tissue, gingiva/periodontium, and dentition.
Secondary involvement may include respiratory muscles, swallowing/feeding function, and variably the heart. (mccarty2025clinicalcharacterizationof pages 7-9, mccarty2025clinicalcharacterizationof pages 2-3, mccarty2025clinicalcharacterizationof pages 3-4, zhu2021ablationofthe pages 16-20)

Suggested UBERON mappings include skeletal muscle tissue (UBERON:0001383), tendon, ligament, dermis, periosteum, periodontium, femur, tibia, patella, knee joint, vertebral column, gingiva, and respiratory muscle. The defect is usually bilateral/generalized; asymmetry may occur on imaging but is not a defining lateralized phenotype.

At the subcellular level, relevant compartments are the endoplasmic-reticulum/secretory pathway for retained dominant-mutant protein and the extracellular/collagen-containing matrix for defective deposition. (punetha2017novelcol12a1variant pages 3-4)

8. Temporal development

Onset is usually prenatal, neonatal, or early childhood: reduced fetal movement, congenital hypotonia, hip dysplasia, arthrogryposis, and motor delay may be the first manifestations. Dominant disease can remain mild through youth and present as slowly progressive distal weakness in the fourth decade; adolescent onset also occurs. (mohassel2019dominantcollagenxii pages 2-3, mccarty2025clinicalcharacterizationof pages 2-3, merlini2025myopathicehlersdanlossyndrome pages 2-3)

The course is chronic and lifelong but not uniformly degenerative. Severe recessive disease produces early disability, respiratory or feeding dependence, and spinal progression. Nonetheless, motor function in the recent recessive cohort often improved slowly without regression. Dominant distal myopathy may progress gradually in adulthood. There are no validated clinical stages, remission pattern, or critical pharmacologic treatment window. Early recognition is important for preventing orthopedic deformity, nutritional compromise, and respiratory complications. (mccarty2025clinicalcharacterizationof pages 7-9, mccarty2025clinicalcharacterizationof pages 2-3)

9. Inheritance and population

Inheritance: autosomal dominant and autosomal recessive.
Recurrence: approximately 50% per pregnancy for a heterozygous affected parent, subject to penetrance and variant interpretation; 25% affected, 50% carrier, and 25% unaffected per pregnancy when both parents carry the same recessive disease allele.
Penetrance: not quantified; dominant expressivity is clearly variable.
Anticipation: not reported.
Founder effects/carrier frequency: none established.
Sex ratio: no reproducible sex bias.
Ethnic/geographic enrichment: none established.

The late-2024 clinical review estimated prevalence at <1 per 1,000,000 and reported 25 individuals from 16 families, including two recessive families. A 2023 review similarly counted 16 families. These are literature counts, not population-based prevalence studies. (dijk2024clinicaldiagnosisof pages 3-4, izu2023collagenxiimediated pages 1-2)

A later 2025 review—outside the requested priority window but informative—compiled approximately 30 dominant patients in 18 families and 15 recessive patients in 13 families, illustrating rapid ascertainment growth and continuing underdiagnosis. (merlini2025myopathicehlersdanlossyndrome pages 1-2)

10. Diagnostics

Clinical recognition

Suspect mEDS when congenital or childhood hypotonia/weakness and motor delay coexist with distal joint hypermobility plus proximal contractures, scoliosis/kyphosis, pes planus, soft skin or abnormal scars, gingival hypertrophy, or a Bethlem/UCMD-like phenotype without a COL6 diagnosis. Minimal clinical criteria in the 2017 EDS framework require congenital muscle hypotonia and/or muscle atrophy that improves with age, plus proximal contractures and/or distal joint hypermobility; molecular confirmation is essential because of overlap. The 2020 cohort used major/minor criteria and included soft doughy skin, atrophic scarring, motor delay, and biopsy-proven myopathy among supporting features. (delbaere2020noveldefectsin pages 2-3)

Testing strategy

Detailed prenatal, developmental, neuromuscular, joint, skin, scar, dental/gingival, respiratory, feeding, cardiac, and three-generation family history.
Physical examination including Beighton score, muscle strength, contractures, spine, patellar stability, skin/scars, palate, and gingiva.
Serum CK—often normal or mildly elevated; a normal result does not exclude disease. (mccarty2025clinicalcharacterizationof pages 2-3, merlini2025myopathicehlersdanlossyndrome pages 2-3)
Pulmonary function testing when developmentally possible; sleep study or blood-gas assessment if respiratory weakness is suspected.
Echocardiography/ECG at baseline where clinically appropriate because cardiac findings occurred in some recessive patients, although dominant-series evidence does not establish routine progressive cardiomyopathy. (mohassel2019dominantcollagenxii pages 2-3, mccarty2025clinicalcharacterizationof pages 2-3)
Muscle MRI can show rectus-femoris, posterior-thigh, neck, lumbar, or diffuse muscle involvement; normal imaging does not exclude mEDS. (mccarty2025clinicalcharacterizationof pages 7-9, mccarty2025clinicalcharacterizationof pages 3-4, merlini2025myopathicehlersdanlossyndrome pages 1-2)
EMG/NCS may be normal. Biopsy, if performed, usually shows mild non-dystrophic myopathy, fiber-size variation, and interstitial connective tissue without prominent necrosis/regeneration. It is supportive rather than diagnostic. (punetha2017novelcol12a1variant pages 3-4, merlini2025myopathicehlersdanlossyndrome pages 7-9)
Molecular confirmation: a comprehensive congenital-myopathy/muscular-dystrophy or heritable-connective-tissue panel including COL12A1, COL6A1, COL6A2, COL6A3, FKBP14, PLOD1, COL5A1/2, TNXB, and other phenotype-relevant genes. Monogenic EDS reviews regard massively parallel gene-panel testing as current gold standard. (dijk2024clinicaldiagnosisof pages 3-4, mccarty2025clinicalcharacterizationof pages 7-9)
If panel testing is negative, use exome or genome sequencing with exon-level CNV and splice analysis. RNA sequencing from fibroblasts may clarify suspected splice variants. Single-gene sequencing is reasonable when the phenotype and familial allele are known.

CMA, karyotype, FISH, mitochondrial-DNA analysis, and repeat-expansion tests are not first-line unless independent clinical findings suggest those mechanisms.

Variant interpretation

Classification should follow ACMG/AMP principles and incorporate rarity, segregation/de novo status, phenotype specificity, predicted effect, RNA evidence, and collagen-XII immunostaining or secretion assays where available. A COL12A1 VUS alone is not diagnostic. (delbaere2020noveldefectsin pages 1-2, ipek2024col12a1genevariant pages 5-6)

Differential diagnosis

Principal differentials are collagen-VI-related Ullrich congenital muscular dystrophy and Bethlem myopathy, FKBP14- and PLOD1-related kyphoscoliotic EDS, classical EDS, TNXB-related classical-like EDS, other congenital myopathies/dystrophies, and congenital contractural disorders. Distal hypermobility plus proximal contractures and mild non-dystrophic biopsy can resemble collagen-VI disease; molecular testing is decisive. (mccarty2025clinicalcharacterizationof pages 7-9, merlini2025myopathicehlersdanlossyndrome pages 1-2)

There is no newborn biochemical screen. Cascade molecular testing is appropriate after identifying a familial pathogenic variant.

11. Outcome and prognosis

No population-based survival, 5- or 10-year survival, life-expectancy, or mortality estimate exists. Typical dominant disease is compatible with prolonged ambulation and often no recognized cardiac or pulmonary disease, although slowly progressive adult weakness occurs. In one literature synthesis, 31/33 dominant cases were ambulant. (mohassel2019dominantcollagenxii pages 2-3, merlini2025myopathicehlersdanlossyndrome pages 7-9)

Recessive disease spans profound neonatal weakness with ventilator/feeding dependence to mild weakness with independent walking. In the recent eight-person biallelic cohort, 5/8 were severe and 3/8 mild-to-moderate; motor improvement without regression was documented. Progressive scoliosis, contractures, joint instability, respiratory failure, feeding impairment, and reduced mobility are major morbidity drivers. (mccarty2025clinicalcharacterizationof pages 7-9, mccarty2025clinicalcharacterizationof pages 2-3)

No prognostic circulating biomarker is validated. Broadly, biallelic null alleles and absent fibroblast collagen XII correlate with greater severity, whereas residual expression is associated with milder disease; variant-level prediction remains imperfect. (mccarty2025clinicalcharacterizationof pages 1-2)

12. Treatment

Current standard of care

There is no approved disease-modifying pharmacotherapy and no evidence-based mEDS-specific treatment algorithm. Management is individualized and multidisciplinary, usually involving clinical genetics, neurology/neuromuscular medicine, rehabilitation, orthopedics, pulmonology, cardiology where indicated, gastroenterology/nutrition, dentistry, pain services, and wound/surgical teams. Evidence is predominantly expert extrapolation from EDS and congenital myopathy rather than controlled mEDS trials. (fajardojimenez2022ehlersdanlosaliterature pages 3-4, islam2021ehlersdanlossyndromeimmunologic pages 23-28, malfait2020theehlers–danlossyndromes pages 15-16)

Physical/occupational therapy: low-impact strengthening, motor training, balance/fall prevention, preservation of range while avoiding aggressive stretching of unstable joints, pacing, and adaptive equipment. Suggested NCIT concepts: Physical Therapy, Occupational Therapy, Exercise Therapy.
Orthoses and mobility aids: braces for unstable joints, ankle-foot orthoses where helpful, and wheelchair/scooter support for severe weakness or pain. Suggested NCIT: Orthotic Device, Assistive Device. (islam2021ehlersdanlossyndromeimmunologic pages 23-28)
Orthopedic care: monitor hip dysplasia, contractures, patellar instability, scoliosis, and kyphosis. Surgery is considered for progressive deformity or failed conservative care; one reported patient’s scoliosis improved after surgery. Tissue fragility and wound healing must be considered. (punetha2017novelcol12a1variant pages 3-4, islam2021ehlersdanlossyndromeimmunologic pages 23-28)
Respiratory care: serial clinical/FVC assessment, cough support, sleep evaluation, and noninvasive or invasive ventilation when required.
Nutrition/feeding: swallowing assessment, nutritional support, and nasogastric/gastrostomy feeding when oral intake is unsafe or insufficient; this is common in severe recessive disease. (mccarty2025clinicalcharacterizationof pages 2-3)
Pain: individualized non-pharmacological and pharmacological management; no mEDS-specific analgesic or pharmacogenomic recommendation exists.
Skin/wounds: minimize trauma and tension; general EDS guidance recommends deep sutures and longer retention where dehiscence is a concern. (islam2021ehlersdanlossyndromeimmunologic pages 23-28)
Dental/periodontal care: surveillance is rational given gingival hypertrophy and dental abnormalities.
Anesthesia: no COL12A1-specific protocol was found; preoperative respiratory, airway, cervical/spinal, joint-positioning, and tissue-fragility assessment is prudent.

Experimental therapy and trials

No relevant registered interventional clinical trial was returned by the ClinicalTrials.gov search, and no approved gene, cell, CRISPR, antisense, siRNA, mRNA, or protein-replacement therapy exists. Allele-specific siRNA restored extracellular collagen-XII distribution in patient fibroblasts carrying an exon-52 deletion, demonstrating targetability but not clinical efficacy or safety. (mohassel2019dominantcollagenxii pages 2-3)

13. Prevention

Primary prevention through lifestyle or vaccination is not applicable to a germline collagenopathy. Immunization follows routine schedules; no infectious prophylaxis is disease-specific.

Secondary prevention consists of early molecular diagnosis, cascade testing, early developmental/rehabilitation services, and surveillance for contractures, scoliosis, respiratory insufficiency, feeding problems, joint instability, and cardiac abnormalities when clinically indicated.

Tertiary prevention includes fall and injury reduction, joint stabilization, careful wound management, contracture/spinal monitoring, nutritional support, and timely ventilatory intervention. General EDS evidence supports conservative strengthening and braces but is not mEDS trial evidence. (islam2021ehlersdanlossyndromeimmunologic pages 23-28)

Genetic counseling should explain dominant and recessive recurrence risks, variable expressivity, and VUS limitations. Once familial pathogenic variant(s) are known, prenatal diagnosis and preimplantation genetic testing are technically possible. Carrier testing is relevant to recessive families; presymptomatic/cascade testing is relevant to dominant families. (malfait2020theehlers–danlossyndromes pages 15-16)

14. Other species and natural disease

No well-established naturally occurring COL12A1-mEDS homolog in companion animals, livestock, or wildlife was identified, and there is no zoonotic or transmissible component. Orthologous collagen-XII genes are conserved across vertebrates, supporting comparative model use, but veterinary prevalence and breed-specific VBO associations are unavailable.

15. Model organisms and experimental systems

Mouse

The principal model is the Col12a1-null mouse (Mus musculus, NCBI Taxon 10090). It recapitulates reduced grip strength, impaired passive muscle force, delayed fiber-type transition, skeletal abnormalities, short stature, kyphosis/kyphoscoliosis, bone fragility, tendon disorganization, patellar subluxation/dislocation, malformed femoral patellar groove, rectus-femoris abnormalities, central nuclei, and fiber-size variation. (delbaere2020noveldefectsin pages 2-3, zou2014recessiveanddominant pages 1-2, zhu2021ablationofthe pages 16-20)

Tendon studies show defective cellular columns and matrix compartmentalization, abnormal fibril masses/spacing, altered cross-sectional area and mechanics, establishing collagen XII as a regulator of hierarchical tendon development. (izu2021collagenxiimediated pages 15-19)

Applications: ECM assembly, mechanotransduction, muscle passive-force transmission, tendon development, patellar stability, bone development, and preclinical target validation.

Limitations: a null mouse best models recessive deficiency, not every dominant-negative human allele; feeding/respiratory severity and human long-term functional variability are incompletely reproduced.

Cellular models

Primary patient dermal fibroblasts are the main human model. They reveal intracellular retention, secretion defects, altered fibril-associated deposition, isoform abnormalities, and secondary decorin/tenascin-X changes. Mutant-allele siRNA rescue provides functional validation. (delbaere2020noveldefectsin pages 1-2, punetha2017novelcol12a1variant pages 3-4, mohassel2019dominantcollagenxii pages 2-3)

No validated mEDS iPSC, organoid, zebrafish, Drosophila, or C. elegans model was established in the retrieved literature.

Recent developments and evidence appraisal

2023 mechanistic synthesis: Izu and Birk integrated extracellular fibrillogenesis with collagen-XII-dependent regulation of cell shape and communication, framing mEDS as both an ECM-structural and cellular-organization disorder. Published 2 March 2023; DOI: https://doi.org/10.3389/fcell.2023.1129000. (izu2023collagenxiimediated pages 1-2)
2023–2024 case expansion: additional recessive splice and nonsense alleles continued to broaden severity, while a 2024 p.Pro2968Leu report emphasized the difficulty of assigning pathogenicity without functional confirmation. DOI for the latter: https://doi.org/10.1159/000536344. (ipek2024col12a1genevariant pages 5-6)
2024 diagnostic consensus: monogenic EDS diagnosis increasingly relies on phenotype-guided massively parallel panel testing rather than clinical labeling alone. Published November 2024; DOI: https://doi.org/10.1515/medgen-2024-2060. (dijk2024clinicaldiagnosisof pages 3-4)
Accepted in 2024/published 2025 recessive cohort: eight additional patients showed that biallelic disease is not uniformly lethal or nonambulant: 3/8 walked independently and motor improvement without regression occurred, while 5/8 had severe congenital disease. DOI: https://doi.org/10.1002/acn3.52225. (mccarty2025clinicalcharacterizationof pages 1-2, mccarty2025clinicalcharacterizationof pages 7-9, mccarty2025clinicalcharacterizationof pages 2-3)

Landmark primary sources

Zou et al., Human Molecular Genetics, May 2014, PMID 24334604, DOI: https://doi.org/10.1093/hmg/ddt627. The title itself captures the central finding: “Recessive and dominant mutations in COL12A1 cause a novel EDS/myopathy overlap syndrome in humans and mice.” (zou2014recessiveanddominant pages 1-2)
The parallel 2014 discovery evidence is indexed under PMID 24334769 in the disease–target association record. (OpenTargets Search: myopathic Ehlers-Danlos syndrome-COL12A1)
Delbaere et al., Genetics in Medicine, January 2020, DOI: https://doi.org/10.1038/s41436-019-0599-6; four novel pathogenic heterozygous exon-skipping defects were found in six patients from four families among 78 unresolved clinically selected individuals. (delbaere2020noveldefectsin pages 1-2, delbaere2020noveldefectsin pages 2-3)

Major knowledge gaps

Reliable incidence, population prevalence, penetrance, carrier frequency, sex ratio, life expectancy, mortality, validated quality-of-life outcomes, longitudinal respiratory/cardiac risk, variant-specific prognosis, biomarkers, and controlled treatment outcomes are unavailable. Likewise absent are disease-specific immune, metabolic, epigenetic, spatial-omics, and advanced human single-cell studies. Published frequencies derive from very small, ascertainment-biased cohorts and should not be interpreted as population estimates.

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(mccarty2025clinicalcharacterizationof pages 3-4): Riley M. McCarty, Dimah Saade, Pinki Munot, Chamindra G. Laverty, Hailey Pinz, Yaqun Zou, Meghan McAnally, Pomi Yun, Cuixia Tian, Ying Hu, Lucy Feng, Rahul Phadke, Sophia Ceulemans, Pilar Magoulas, Andrew J. Skalsky, Jennifer R. Friedman, Stephen R. Braddock, Sarah B. Neuhaus, Denise M. Malicki, Matthew N. Bainbridge, Shareef Nahas, David P. Dimmock, Stephen F. Kingsmore, Timothy E. Lotze, A. Reghan Foley, Francesco Muntoni, Volker Straub, Sandra Donkervoort, and Carsten G. Bönnemann. Clinical characterization of collagen xii‐related disease caused by biallelic col12a1 variants. Annals of Clinical and Translational Neurology, 12:602-614, Feb 2025. URL: https://doi.org/10.1002/acn3.52225, doi:10.1002/acn3.52225. This article has 4 citations and is from a peer-reviewed journal.
(zhu2021ablationofthe pages 16-20): Mengjie Zhu, Fabian Metzen, Janina Betz, Mark Hopkinson, Juliane Heilig, Thomas Imhof, Anja Niehoff, David E. Birk, Yayoi Izu, Andrew A. Pitsillides, Janine Altmüller, Gudrun Schreiber, Mats Paulsson, Manuel Koch, and Bent Brachvogel. Ablation of the facit collagen xii disturbs musculoskeletal ecm organization and causes patella dislocation and myopathy. bioRxiv, Dec 2021. URL: https://doi.org/10.1101/2021.12.29.474475, doi:10.1101/2021.12.29.474475. This article has 0 citations.
(izu2021collagenxiimediated pages 15-19): Yayoi Izu, Sheila M. Adams, Brianne K. Connizzo, David P. Beason, Louis J. Soslowsky, Manuel Koch, and David E. Birk. Collagen xii mediated cellular and extracellular mechanisms regulate establishment of tendon structure and function. Jan 2021. URL: https://doi.org/10.1016/j.matbio.2020.10.004, doi:10.1016/j.matbio.2020.10.004. This article has 48 citations and is from a domain leading peer-reviewed journal.
(chiquet2014collagenxiiprotecting pages 9-11): Matthias Chiquet, David E. Birk, Carsten G. Bönnemann, and Manuel Koch. Collagen xii: protecting bone and muscle integrity by organizing collagen fibrils. Aug 2014. URL: https://doi.org/10.1016/j.biocel.2014.04.020, doi:10.1016/j.biocel.2014.04.020. This article has 131 citations.
(dijk2024clinicaldiagnosisof pages 3-4): Fleur S. van Dijk, Chloe Angwin, Serwet Demirdas, Neeti Ghali, and Johannes Zschocke. Clinical diagnosis of the monogenic ehlers-danlos syndromes. Medizinische Genetik, 36:225-234, Nov 2024. URL: https://doi.org/10.1515/medgen-2024-2060, doi:10.1515/medgen-2024-2060. This article has 4 citations.
(fajardojimenez2022ehlersdanlosaliterature pages 3-4): María José Fajardo-Jiménez, Johanna A. Tejada-Moreno, Alejandro Mejía-García, Andrés Villegas-Lanau, Wildeman Zapata-Builes, Jorge E. Restrepo, Gina P. Cuartas, and Juan C. Hernandez. Ehlers-danlos: a literature review and case report in a colombian woman with multiple comorbidities. Nov 2022. URL: https://doi.org/10.3390/genes13112118, doi:10.3390/genes13112118. This article has 2 citations.
(islam2021ehlersdanlossyndromeimmunologic pages 23-28): Mareesa Islam, Christopher Chang, and M. Eric Gershwin. Ehlers-danlos syndrome: immunologic contrasts and connective tissue comparisons. Jan 2021. URL: https://doi.org/10.1016/j.jtauto.2020.100077, doi:10.1016/j.jtauto.2020.100077. This article has 40 citations and is from a peer-reviewed journal.
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Artifacts

Edison artifact artifact-00

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	17
Resolved	17
Unresolved (possible confabulation)	0
Unverifiable	0
References weighed for topical relevance	17
On topic	8
Off topic	0

All extracted references resolved successfully.

Term Validation

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

Outcome	Count
Terms checked	43
Resolved	40
Unresolved (possible confabulation)	1
Obsolete	2
Unverifiable	0
Terms whose name was checked	1
Terms named correctly	0
Terms named as a different term	1

Terms the report names something else

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

MONDO:0034022 (2 mentions) - the report calls it "if available"; MONDO calls it Bethlem myopathy 2

Unresolved terms

These identifiers do not exist in an ontology that resolved other terms from the same prefix, so they were most likely invented:

HP:0002802 (2 mentions) - HP does not contain this term

Obsolete terms

These terms are real but deprecated. Citing one is not a fabrication; it does mean the report is naming something the ontology has retired:

HP:0002355 (obsolete Difficulty walking) (2 mentions) - replaced by HP:0001288
GO:0062023 (obsolete collagen-containing extracellular matrix) (2 mentions) - replaced by GO:0031012

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OpenScientist Report

Inheritance

Subtypes

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Diagnosis

Prevalence

Source YAML

References & Deep Research

References

Deep Research

Myopathic Ehlers–Danlos Syndrome (mEDS): Disease-Characteristics Report

Executive summary

1. Disease information

Definition and nomenclature

Identifiers

2. Etiology

Causal factor

Genetic risk

Non-genetic, protective, and gene–environment factors

3. Phenotypes

Principal phenotype annotations

Quality of life

4. Genetic and molecular information

Gene and protein

Variant classes and consequences

Modifiers, epigenetics, and chromosomal abnormalities

5. Environmental information

6. Mechanism and pathophysiology

Ordered causal chain

Pathways and processes

Cells and tissues

Molecular profiling

7. Anatomical structures affected

8. Temporal development

9. Inheritance and population

10. Diagnostics

Clinical recognition

Testing strategy

Variant interpretation

Differential diagnosis

11. Outcome and prognosis

12. Treatment

Current standard of care

Experimental therapy and trials

13. Prevention

14. Other species and natural disease

15. Model organisms and experimental systems

Mouse

Cellular models

Recent developments and evidence appraisal

Landmark primary sources

Major knowledge gaps

Artifacts

Reference Validation

Term Validation

Terms the report names something else

Unresolved terms

Obsolete terms