Congenital Merosin-deficient Muscular Dystrophy 1A

Mendelian MONDO:0011925 Pathograph 66 Show in embeddings browser LAMA2-related muscular dystrophy Congenital Muscular Dystrophy

MDC1A is the severe congenital end of LAMA2-related muscular dystrophy. Biallelic pathogenic LAMA2 variants impair laminin alpha-2, a component of laminin-211 in muscle, peripheral nerve and CNS basement membranes. Loss of basal-lamina anchorage and laminin-dependent signalling makes muscle fibres vulnerable to injury; degeneration, altered protein turnover, impaired repair and fibrosis contribute to weakness and contractures. Human infant muscle histology demonstrates early degeneration, while the timing and contributions of apoptosis, inflammation and autophagy are most directly tested in animal and cell models. Regeneration is impaired rather than universally absent, and some injured fibres survive or recover in models. Severe early hypotonia and axial/proximal weakness delay motor development and usually prevent independent walking. Progressive contractures, spinal deformity, respiratory muscle weakness and impaired feeding add substantial morbidity. Clinical cohorts distinguish the congenital phenotype from complete merosin deficiency: these categories overlap strongly but are not interchangeable. Partial deficiency can accompany an early severe phenotype, and occasional patients classified as completely deficient walk independently. Young children may gain skills before later functional decline. Peripheral myelin abnormalities and motor conduction slowing are variable and generally contribute less to human weakness than in mouse models. White-matter MRI signal changes are very frequent after infancy and may appear by three months. Increased white-matter water content is supported by human MR spectroscopy; a vascular basement-membrane mechanism remains a hypothesis, and diffuse human demyelination is not established by the MRI appearance. Cortical neuronal migration abnormalities can contribute to seizures and intellectual disability in a subset, but neither clinical consequence is inevitable and seizures can occur without a visible cortical malformation. This entry focuses on congenital MDC1A, with explicitly identified observations from the broader partial-deficiency and limb-girdle LAMA2 spectrum. Residual protein is associated with severity but does not reliably predict an individual's trajectory. Care addresses respiratory, nutritional, orthopedic and cardiac complications; preclinical therapeutic effects and the phase 1 omigapil safety study do not establish clinical disease-modifying efficacy.

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Classifications

Harrison's Part

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Mappings

MONDO

MONDO:0100228 LAMA2-related muscular dystrophy Not Yet Curated

MONDO:0011925 identifies the congenital disease emphasized here. MONDO:0100228 denotes the broader LAMA2-related muscular dystrophy spectrum, from which explicitly scoped comparative observations are included; it is a broad match rather than an equivalent label for MDC1A.

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Inheritance

Autosomal recessive HP:0000007

Biallelic LAMA2 variants, homozygous or compound heterozygous. Truncating alleles predominate in the congenital severe form; missense alleles are over-represented in the milder limb-girdle form, which is the molecular basis of the complete/partial deficiency split.

Autosomal recessive inheritance

Show evidence (2 references)

PMID:22675738 SUPPORT Other

"The diagnosis of LAMA2 muscular dystrophy is established in a proband with suggestive findings and biallelic (homozygous or compound heterozygous) pathogenic variants in LAMA2 identified by molecular genetic testing."

States the biallelic requirement that defines the recessive mode.

PMID:34281576 SUPPORT Human Clinical

"Nonsense variants were more frequent in LAMA2-CMD (56.9%, 66/116) than in LGMDR23 (21.4%, 3/14), while missense disease-causing variants were more frequent in LGMDR23 (71.4%, 10/14) than in LAMA2-CMD (12.9%, 15/116)."

Quantifies the allele-class skew between the congenital and limb-girdle ends of the same recessive series.

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Subtypes

Complete deficiency of merosin

Absent laminin alpha-2 on muscle immunostaining, usually associated with a severe congenital phenotype and failure to achieve independent walking. Some cohorts classify deficiency using genotype or clinical information when biopsy is unavailable. Complete deficiency and congenital clinical onset are correlated but not identical categories; rare ambulant exceptions occur.

Show evidence (1 reference)

PMID:32848593 SUPPORT Other

"Muscle atrophy and severe weakness typically prevent independent ambulation."

States the defining functional consequence of the complete-deficiency phenotype.

Partial deficiency of merosin

Reduced but detectable laminin alpha-2 is often associated with a milder limb-girdle presentation and retained ambulation. Partial deficiency is not synonymous with late onset: congenital, severe presentations also occur. Cohorts classified by clinical onset or walking ability cannot be read as immunostaining-defined subgroups.

Show evidence (3 references)

PMID:32848593 SUPPORT Other

"Partial merosin deficiency is mostly manifested by later onset limb-girdle weakness and joint contractures so that independent ambulation is typically achieved."

Defines the partial-deficiency phenotype and its ambulatory outcome.

PMID:9829280 SUPPORT Human Clinical

"These data confirm that mutations of the LAMA2 gene that do not completely disrupt the production of the protein can give rise to phenotypes considerably milder than classical merosin-deficient congenital muscular dystrophy."

Establishes the residual-protein rule that makes this a graded subtype of the same disease rather than a distinct entity.

PMID:34281576 SUPPORT Human Clinical

"All LGMDR23 patients achieved independent ambulation at median age of 18.0 months (range 13.0-20.0 months)."

All clinically classified LGMDR23 patients in this cohort walked independently; this is not a direct estimate for every patient with partial merosin staining.

Discussions and Knowledge Gaps

Residual clinical attribution and model translation

KNOWLEDGE GAP mdc1a-gap-1

Attached to

phenotypes#Ophthalmoparesis phenotypes#Macroglossia phenotypes#Gastroesophageal reflux phenotypes#Reduced bone mineral density phenotypes#Spinal rigidity phenotypes#Neck rigidity phenotypes#Hip dislocation phenotypes#Pectus excavatum phenotypes#Pectus carinatum phenotypes#Weak cry

The clinical findings are documented, but the reviewed sources do not establish a specific upstream causal route for each. Extraocular muscle involvement differs between mouse models and human ophthalmoparesis; tongue enlargement is not explained by a demonstrated tissue mechanism. Low bone density may have several determinants, and the cohort did not establish immobility as its sole cause. Reflux, neck and spine rigidity, hip and chest deformities, and weak cry have incompletely resolved contributions from muscle injury, fibrosis, posture or other factors. A qualified model-supported masticatory injury pathway is represented, but it does not establish the relative human contribution of muscle weakness, contracture and tongue enlargement. Supported oral-phase, nutritional and respiratory consequences are represented separately.

Posterior fossa developmental abnormalities

KNOWLEDGE GAP mdc1a-gap-2

Attached to

phenotypes#Pontine hypoplasia phenotypes#Enlarged cisterna magna phenotypes#Blake pouch cyst

Pontine hypoplasia and posterior-fossa configuration abnormalities are documented in the Swiss imaging cohort, but their specific developmental connection to LAMA2 loss was not established. Cortical overmigration cannot automatically be extended to these anatomically distinct findings. A case-specific cyst-to-hydrocephalus relation is represented; these findings are not assumed to explain seizures.

Show evidence (1 reference)

PMID:39213089 SUPPORT Human Clinical

"Three out of four patients with epilepsy showed structural abnormalities on brain MRI (pontine hypoplasia = 3, Blake’s pouch cyst = 1, and mega cisterna magna = 1) but these abnormalities are not associated with epilepsy; only two of the patients had cortical malformations."

The authors distinguish posterior-fossa/brainstem abnormalities from potentially epileptogenic cortical lesions.

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Pathophysiology

Biallelic LAMA2 Loss of Function

Two damaged copies of LAMA2, at 6q22-q23, remove or truncate the laminin alpha-2 chain. Most congenital-severe alleles are premature termination codons or exon deletions; missense alleles that leave residual protein are enriched at the milder end of the spectrum. Because laminin-211 is an obligate alpha2-beta1-gamma1 heterotrimer, loss of the single alpha-2 chain removes the assembled trimer rather than merely weakening it.

LAMA2 hgnc:6482

Downstream

Loss of Laminin-211 from the Muscle Basal Lamina The alpha-2 chain is the isoform-defining subunit of laminin-211, so a null allele pair removes the trimer from every basement membrane that depends on it.

Loss of Laminin-211 from the Schwann Cell Basal Lamina The same null genotype removes laminin-211 from Schwann cell basal laminae, where the alpha-2 chain is likewise the predominant laminin alpha subunit.

Loss of Laminin-211 at the Glia Limitans and CNS Vascular Basement Membranes Laminin alpha-2 is deposited by astrocyte endfeet, so a systemic null genotype withdraws it from the pial and perivascular basement membranes of the brain as well.

Dysregulated Muscle Proteostasis and Autophagy Laminin-alpha2 deficiency alters muscle proteostasis in experimental models; the intervening signalling and human causal contribution remain incompletely established.

Impaired Muscle Regeneration Loss of cell-autonomously secreted laminin-alpha2 slows myogenic precursor proliferation in engineered human cells and delays regeneration in muscle stem-cell-specific mouse knockouts.

Loss of Myocardial Laminin-211 Support Systemic LAMA2 deficiency affects laminin-alpha2-dependent myocardial matrix; the cardiac physiological consequence is provisional.

Show evidence (2 references)

PMID:7550355 SUPPORT Human Clinical

"We therefore investigated LAMA2 for the presence of disease-causing mutations in laminin alpha 2 chain-deficient CMD families and now report splice site and nonsense mutations in two families leading presumably to a truncated laminin alpha 2 protein."

The original report establishing LAMA2 as the mutated gene and truncation as the allele class.

PMID:34281576 SUPPORT Human Clinical

"The top three high-frequency disease-causing variants in Han Chinese patients were c.7147C > T (p.R2383*), exon 4 deletion, and c.5156_5159del (p.K1719Rfs*5)."

Shows that the recurrent alleles in a large cohort are nonsense, whole-exon deletion and frameshift, that is, loss-of-function classes.

Loss of Laminin-211 from the Muscle Basal Lamina

Laminin-211 is the predominant laminin of the skeletal-muscle basement membrane. Without the alpha-2 chain the basal lamina loses both its principal polymerising alpha subunit and the long-arm LG module that tethers the lattice to the fibre surface, so the sheet is destabilised and its cell-facing end is unanchored.

laminin-211 as a basement-membrane structural constituent GO:0005201 ↓ DECREASED

muscle fibre basal lamina GO:0005604

Downstream

Failure of Basal Lamina to Sarcolemma Receptor Coupling The receptors remain in the membrane but their ligand is gone, so the linkage fails from the matrix side.

Show evidence (1 reference)

PMID:31308722 SUPPORT Other

"Laminin-211 is an extracellular matrix protein that functions to stabilize the basement membrane and muscle fibers during contraction."

States the structural role of laminin-211 in the muscle basement membrane that this node reports as lost.

Failure of Basal Lamina to Sarcolemma Receptor Coupling

Laminin-211 connects basal lamina with sarcolemmal dystroglycan and integrin alpha-7-beta-1 receptor systems. Its loss weakens matrix-to-cytoskeletal anchorage and adhesion-dependent signalling; receptor abundance and compensating laminin expression can also change. Loss of laminin-211 does not mean that every extracellular-matrix attachment is absent.

myofibre adhesion to the basal lamina GO:0031589 ↓ DECREASED

laminin-211 binding by alpha-dystroglycan and integrin alpha-7-beta-1 GO:0043236 ↓ DECREASED

Animal models

dyW/dyW laminin alpha2-deficient mouse Mouse perturbs Used as the test bed for restoring the coupling directly. Transgenic mini-agrin, which binds dystroglycan but not integrin alpha-7-beta-1, and a perlecan-derived chimeric protein each ameliorate the disease, including when expression is started late. Separately, transgenic integrin alpha-7 overexpression restores sarcolemmal alpha-7-beta-1 and improves pathology and life expectancy. Together these attack the two arms of the lost linkage independently.

Downstream

Contraction-Induced Myofibre Detachment and Mechanical Injury With the mechanical arm of the bridge gone, contractile force is no longer transmitted across an intact linkage and the fibre pulls away from its matrix.

Loss of Laminin-Dependent Survival Signalling The same receptors carry adhesion-dependent survival signalling, so the signalling arm fails at the same moment as the mechanical one.

Show evidence (4 references)

PMID:21798088 SUPPORT Other

"By binding to the cell surface receptors dystroglycan and integrin α7β1, laminin-211 is believed to protect the muscle fiber from damage under the constant stress of contractions, and to influence signal transmission events."

States both arms of the linkage, mechanical protection and signal transmission, that this node reports as jointly lost.

PMID:37182895 SUPPORT Other

"the LG domain (LG), which binds to the glycosylated residues of α-dystroglycan and to the integrins"

Identifies the LG module as the receptor-binding domain, which is the structural basis for the coupling described here.

PMID:32827036 SUPPORT Other

"This results in a loss of the stabilizing connection to the DGC, leading to a loss of structural integrity and function of various cells, including myocytes and Schwann cells"

States the loss of the dystroglycan-complex connection following failure of merosin to serve as a matriglycan acceptor, which is the dystroglycan arm of this node.

+ 1 more reference

Contraction-Induced Myofibre Detachment and Mechanical Injury

Loss of laminin-dependent anchorage permits contraction-associated fibre detachment and injury. In lama2-deficient zebrafish, detached fibres retain membrane integrity and many survive or reattach; detachment is not synonymous with immediate cell death. Early pharmacological inhibition of contraction reduces larval structural damage but also impairs force development in mutants and controls. Damage reappears after washout in Candyfloss mutants, supporting activity-dependent injury without demonstrating human therapeutic benefit.

skeletal muscle fibre CL:0008002

skeletal muscle tissue UBERON:0001134

Animal models

lama2 mutant zebrafish Zebrafish recapitulates Reproduces myofibre detachment from the basal lamina and, uniquely, allows it to be watched in a living animal fibre by fibre.

Downstream

Myofibre Degeneration, Necrosis and Apoptosis Loss of anchorage increases vulnerability to degeneration, but not every detached fibre dies. The timing and route differ between experimental models and are not directly tracked in human muscle.

Show evidence (3 references)

PMID:31754462 SUPPORT Model Organism

"Here we show, via live tracking of individual muscle fibres, that dystrophic myofibres in the zebrafish model of MDC1A maintain sarcolemmal integrity and undergo dynamic remodelling behaviours post detachment, including focal sarcolemmal reattachment, cell extension and hyper-fusion with..."

Directly observes myofibre detachment in a laminin-deficient animal and characterises what the fibre does next.

PMID:26536238 SUPPORT Model Organism

"A key finding of this study is that the BTS immobilization reduced the muscle damage occurring in freely moving Sap and Caf larvae. Although BTS treatment generally weakened muscle function, as discussed above, it also abolished the difference in force between the mutated larvae and their normal..."

BTS exposure from 18 hours to 4 days post-fertilization reduced structural damage in Candyfloss lama2 mutants and Sapje dystrophin mutants. Force was also reduced in both mutants and normal siblings, so structural protection is not restoration of normal contractile function.

PMID:26536238 SUPPORT Model Organism

"We thus consider BTS to abolish contraction in the larvae via direct effects on the contractile system, without interfering with motor nerves, muscle activation or imposing external constraints."

The authors interpret this actin-myosin inhibitor as mechanical silencing through the contractile apparatus, not motor-nerve paralysis or external restraint. The experiment supports activity-dependent injury in larvae without establishing membrane rupture, a specific human effect size, or clinical benefit from immobilization.

Loss of Laminin-Dependent Survival Signalling

Merosin promoted stability and prevented apoptosis in cultured human rhabdomyosarcoma and mouse C2C12 myogenic cell lines. These were not patient-derived myoblasts. The assay supports a survival-signalling function but does not establish that other laminins can never compensate in vivo.

myofibre apoptosis GO:0010657 ↑ INCREASED

Downstream

Myofibre Degeneration, Necrosis and Apoptosis Loss of laminin-dependent survival signalling can promote myotube apoptosis in culture; translation to its quantitative contribution to human fibre loss remains uncertain.

Show evidence (2 references)

PMID:8830776 SUPPORT In Vitro

"Finally, merosin appears to promote myotube stability by preventing apoptosis."

States the anti-apoptotic function of merosin whose loss this node describes.

PMID:8830776 SUPPORT In Vitro

"Exogenous merosin converted these myotubes to a stable phenotype, while laminin had no effect."

Merosin rescued myotube stability in the tested cell lines; the negative laminin comparison is assay-specific, not a universal prohibition on paralog compensation.

Myofibre Degeneration, Necrosis and Apoptosis

Fibres die by both necrosis and apoptosis, and the apoptotic component is unusually prominent for a muscular dystrophy, prominent enough to be a therapeutic target in its own right. In the dy3K/dy3K null mouse, apoptotic fibres are already present at postnatal day 1, before any other dystrophic hallmark. That two Bcl-2-family manipulations, and separately a GAPDH-Siah1 pathway inhibitor, each extend survival severalfold makes apoptosis causal here rather than incidental.

skeletal muscle fibre CL:0008002

muscle cell apoptotic process GO:0010657 ↑ INCREASED

Animal models

dy3K/dy3K laminin alpha2 null mouse Mouse recapitulates Reproduces the apoptotic and necrotic myofibre death of the human disease and dates its onset to the first postnatal day.

dyW/dyW laminin alpha2-deficient mouse Mouse recapitulates Apoptotic fibre death is present and is causally load-bearing: removing Bax or overexpressing Bcl-2 each produce a severalfold lifespan increase, and Bax inactivation also improves growth, histology and contractures.

Downstream

Inflammatory Cell Recruitment Degenerating and necrotic fibres recruit macrophages, and the infiltrate appears within days of birth in the null mouse.

Impaired mastication Dystrophic injury of masticatory muscles is a plausible contributor to impaired chewing. The tissue distribution and nutritional effect are supported in dy3K mice, while the quantitative contribution to human feeding difficulty remains uncertain.

Show evidence (4 references)

PMID:31586140 SUPPORT Model Organism

"We found that apoptotic muscle fibres were present as early as postnatal day 1."

Places myofibre apoptosis at the earliest detectable point of the disease in the complete-null model.

PMID:15578095 SUPPORT Other

"Laminin-alpha2-deficient skeletal muscles in both humans and mice show signs of muscle cell death by apoptosis."

This is a background synthesis of prior human and mouse observations, distinct from the paper’s mouse Bax/Bcl-2 intervention results.

PMID:31586140 SUPPORT Other

"Typical hallmarks of LAMA2-CMD dystrophic muscle biopsy include: degenerating/regenerating muscle fibres, muscle fibre atrophy, necrosis and apoptosis of muscle cells, early inflammation and extensive connective tissue infiltration"

This introductory summary describes known biopsy hallmarks; the primary time-course experiment was in dy3K mice.

+ 1 more reference

Dysregulated Muscle Proteostasis and Autophagy

Mechanism confidence: Provisional

Autophagy-related transcripts are increased in sampled human and dy3K mouse muscle. The nonspecific inhibitor 3-methyladenine improved several mouse outcomes, supporting a contribution of altered protein turnover. Transcript abundance and this intervention do not establish uniformly excessive autophagic flux or an exclusively harmful role in patients.

macroautophagy GO:0016236 ↑ INCREASED

Animal models

dy3K/dy3K laminin alpha2 null mouse Mouse recapitulates Autophagy-related gene expression is raised in dy3K/dy3K muscle, and the same upregulation was confirmed in human MDC1A muscle, so the model is not merely analogous here.

Downstream

Muscle Atrophy and Loss of Muscle Mass Mouse 3-methyladenine treatment supports a contribution of altered degradation to atrophy, with uncertain pathway specificity and human effect size.

Show evidence (1 reference)

PMID:21920942 SUPPORT Other

"Using the dy(3K)/dy(3K) mouse model of laminin α2 chain deficiency and MDC1A patient muscle, we show here that expression of autophagy-related genes is upregulated in laminin α2 chain-deficient muscle."

The quoted claim combines human tissue and mouse expression data; the interventional causal evidence is separately assigned to the mouse model.

Impaired Muscle Regeneration

Laminin-alpha2 deficiency can impair muscle stem-cell proliferation and delay repair. Regeneration remains possible: mouse and zebrafish studies show repair and fibre recovery. LAMA2 knockout in healthy-donor isogenic human iPSC-derived myogenic precursors slowed cell-cycle progression, while differentiation remained possible; this is cell-model evidence rather than a measured patient stem-cell defect.

skeletal muscle satellite cell CL:0000594

skeletal muscle tissue regeneration GO:0043403 ↓ DECREASED

Downstream

Endomysial Fibrosis and Replacement of Muscle What regeneration fails to replace is replaced by connective tissue instead.

Muscle Atrophy and Loss of Muscle Mass Repair that cannot keep pace with degeneration contributes to loss of muscle mass; impaired fibre growth and increased protein degradation also contribute.

Show evidence (3 references)

PMID:31754462 SUPPORT Model Organism

"We further reveal that Laminin also acts as a pro-regenerative factor that stimulates muscle stem cell-mediated repair in lama2-deficient animals in vivo."

Shows the regenerative deficit is itself laminin-dependent, which is the specific claim this node makes.

PMID:35203715 SUPPORT Other

"Consequently, MDC1A-causing mutations in the LAMA2 gene lead to a defective muscle repair associated with chronic inflammation, fibrosis, and muscle atrophy"

States the defective-repair-to-fibrosis-and-atrophy sequence that this node and its downstream targets describe.

PMID:41309582 SUPPORT In Vitro

"This indicated that deletion of LAMA2 in human myogenic precursor cells is sufficient to slow cell-cycle progression."

Engineered LAMA2 knockout in healthy-donor iPSC-derived myogenic precursors, not patient cells, establishes a culture-level proliferative defect.

Inflammatory Cell Recruitment

Inflammatory infiltration accompanies early fibre injury and persists in dystrophic mouse muscle. Chronic inflammatory signalling can impair myogenesis and sustain fibroblast activation, but early inflammatory and matrix responses can also support repair; their effect depends on timing and context.

macrophage CL:0000235

inflammatory response GO:0006954 ↑ INCREASED

Downstream

Endomysial Fibrosis and Replacement of Muscle Chronic infiltrate is the standard driver of mesenchymal activation and matrix deposition in injured muscle.

Increased endomysial connective tissue Persistent inflammation and fibroblast activation promote matrix deposition in chronically injured muscle; this upstream relation is distinct from equating biopsy collagen with a fibrosis node.

Show evidence (2 references)

PMID:35203715 SUPPORT Other

"In DyW mice, a murine model of laminin-deficient muscular dystrophy, merosin-deficient skeletal muscles exhibit high macrophage infiltration from early ages to adulthood."

Documents the early and sustained macrophage infiltration this node reports.

PMID:31586140 SUPPORT Model Organism

"Other typical dystrophic hallmarks (muscle degeneration, inflammation, and extensive production of the extracellular matrix proteins) were clearly evident already at postnatal day 4, and the highest degree of muscle deterioration was reached by day 7."

Times the inflammatory infiltrate and matrix production to the first postnatal week in the complete-null model.

Endomysial Fibrosis and Replacement of Muscle

Persistent fibroblast activation and matrix deposition accompany muscle degeneration and impaired repair. Fibrogenesis can contribute to early contractures; the timing and cellular contributions in individual human muscles are less directly resolved than in experimental models.

myofibroblast CL:0000186

extracellular matrix organization GO:0030198 ↑ INCREASED

Animal models

dy2J/dy2J splice-mutant mouse Mouse rescues Upregulating the paralogous laminin-alpha1 prevented fibrosis and paralysis when given pre-symptomatically, and improved and partly reversed both when given after they were established.

Downstream

Joint contracture Fibrogenesis shortens and stiffens muscle and periarticular tissues, contributing to early and progressive flexion contractures.

Elbow flexion contracture The documented joint-specific contracture is a clinical consequence of the general fibrogenic shortening process; the cited mechanism is not a joint-specific intervention experiment.

Knee flexion contracture The documented joint-specific contracture is a clinical consequence of the general fibrogenic shortening process; the cited mechanism is not a joint-specific intervention experiment.

Hip flexion contracture The documented joint-specific contracture is a clinical consequence of the general fibrogenic shortening process; the cited mechanism is not a joint-specific intervention experiment.

Ankle contracture The documented joint-specific contracture is a clinical consequence of the general fibrogenic shortening process; the cited mechanism is not a joint-specific intervention experiment.

Finger flexion contracture The documented joint-specific contracture is a clinical consequence of the general fibrogenic shortening process; the cited mechanism is not a joint-specific intervention experiment.

Show evidence (2 references)

PMID:39213089 SUPPORT Other

"Pathophysiologically, early fibrogenesis results in severe and early contractures of joints and loss of muscle tissue by myofibroblast transdifferentiation"

The cohort introduction summarizes a fibrogenic mechanism from prior work rather than directly testing it in these patients.

PMID:7550355 SUPPORT Other

"Histological changes seen in muscle biopsies consist of large variations in muscle fibre size, a few necrotic and regenerating fibres and a marked increase in endomysial collagen tissue."

Records the endomysial collagen increase as a defining biopsy feature of this disease group.

Muscle Atrophy and Loss of Muscle Mass

Muscle mass is reduced by fibre injury, inadequate repair and altered protein turnover. Atrophy is not solely a count of lost fibres: dy3K muscle can regain fibre number while retaining small fibres. Axial and proximal clinical weakness cannot itself quantify the amount of atrophy.

skeletal muscle tissue UBERON:0001134

Downstream

Axial muscle weakness Loss and dysfunction of contractile tissue contribute to axial force loss; tissue amount is not the sole determinant of strength.

Proximal muscle weakness The same muscle degeneration and atrophy contribute to proximal limb weakness; the distribution is supported independently by clinical examination.

Facial muscle weakness Facial muscle involvement is part of the myopathic process; the precise contribution of fibre loss versus dysfunction is not quantified.

Neonatal hypotonia Early dystrophic muscle injury and loss of effective contractile tissue contribute to low tone in congenital disease; tone and strength remain distinct clinical findings.

Respiratory Muscle Weakness and Reduced Chest Wall Compliance The muscle disease affects intercostal and accessory muscles, reducing effective respiratory force and chest-wall expansion.

Show evidence (1 reference)

PMID:31308722 SUPPORT Other

"Besides impaired regeneration, the imbalance between protein synthesis and protein breakdown is another factor leading to loss of muscle mass and muscle atrophy in LAMA2 MD."

Review synthesis of impaired repair and protein turnover, rather than inference of atrophy from motor-function scores.

Respiratory Muscle Weakness and Reduced Chest Wall Compliance

Weak intercostal and accessory muscles reduce chest-wall expansion, lung volume and gas exchange. Spinal deformity can add thoracic restriction or airway compression. This mechanism explains restrictive physiology and respiratory insufficiency; human studies show relative functional diaphragm preservation despite severe overall disease.

Downstream

Restrictive ventilatory defect Reduced chest-wall expansion and lung volumes produce restrictive ventilatory physiology.

Respiratory insufficiency due to muscle weakness Impaired ventilation and gas exchange can progress to clinically significant respiratory insufficiency.

Impaired Respiratory Secretion Clearance Respiratory muscle weakness limits effective cough and secretion clearance.

Show evidence (1 reference)

PMID:31308722 SUPPORT Other

"Weakness of intercostal and accessory muscles results in progressive restriction of the chest wall, decreased lung volume, reduced alveolar gas exchange, and eventually restrictive respiratory insufficiency."

The clinical mechanistic review explicitly states the respiratory causal sequence.

Loss of Laminin-211 from the Schwann Cell Basal Lamina

Laminin-alpha2 in Schwann-cell basal lamina supports axonal sorting and myelin organization. Deficiency can disturb developmental myelination; variable human nerve pathology does not justify excluding superimposed demyelination or remyelination in all patients.

Schwann cell CL:0002573

Downstream

Peripheral Dysmyelination Without its basal-lamina ligand the Schwann cell cannot build normal compact myelin.

Show evidence (2 references)

PMID:8576559 SUPPORT Human Clinical

"Because the alpha 2 subunit is also expressed in S-merosin, found in Schwann cells, we have investigated whether peripheral nerve function is also affected in these patients."

Establishes Schwann-cell expression of the alpha-2 chain, which is what this node reports as lost.

PMID:31341277 SUPPORT Other

"MDC1A is caused by mutations in LAMA2 that lead to nonfunctional laminin-α2, which compromises the stability of muscle fibres and the myelination of peripheral nerves."

States the peripheral-nerve myelination arm alongside the muscle arm.

Peripheral Dysmyelination

Peripheral myelin abnormalities accompany some cases, with variable motor conduction slowing. A mildly affected partial-deficiency patient had biopsy evidence of abnormal myelinogenesis; that case cannot define every severe congenital neuropathy. Human functional contribution is usually limited compared with the marked peripheral nerve phenotype of some mouse models.

Schwann cell CL:0002573

myelination in peripheral nervous system GO:0022011 ↓ DECREASED

peripheral nervous system UBERON:0000010

Show evidence (4 references)

PMID:8576559 SUPPORT Human Clinical

"All but two of the 10 merosin-deficient cases had reduced motor nerve conduction, whereas all the merosin-positive cases had normal results."

Ties the conduction slowing specifically to merosin deficiency rather than to congenital muscular dystrophy in general.

PMID:12661054 SUPPORT Human Clinical

"Nerve biopsy showed reduction of large myelinated fibers, short internodes, enlarged nodes, excessive variability of myelin thickness, tomacula, and uncompacted myelin, but no evidence of segmental demyelination, naked axons, or onion bulbs."

These findings came from a mildly affected patient with partial muscle merosin deficiency; the absence of segmental demyelination in that case is not a disease-wide rule.

PMID:12661054 SUPPORT Human Clinical

"Thus, in congenital muscular dystrophy, merosin expression may be dissociated in different tissues, and the neuropathy is sensory-motor and due to abnormal myelinogenesis."

The authors interpret the neuropathy in this partial-deficiency case as abnormal myelinogenesis.

+ 1 more reference

Loss of Laminin-211 at the Glia Limitans and CNS Vascular Basement Membranes

In the brain the alpha-2 chain is contributed by astrocyte foot processes at the glia limitans and the blood-brain barrier. Its loss therefore destabilises two distinct CNS basement-membrane compartments: the perivascular one, whose failure is the leading explanation for the white-matter signal change, and the pial one, whose failure permits cortical overmigration.

astrocyte endfoot at the glia limitans CL:0000127

CNS basement membrane GO:0005604

Downstream

Increased Cerebral White Matter Water Content Increased white-matter water is attributed provisionally to impaired blood-brain barrier filtration after laminin-alpha2 loss. Human MR measurements support increased water, while the permeability mechanism remains a hypothesis and alternative myelin-related contributions are unresolved.

Pial Basement Membrane Assembly Failure The glia limitans is a laminin-dependent basement membrane, so withdrawal of its principal alpha chain is an assembly defect.

Show evidence (1 reference)

PMID:32827036 SUPPORT Other

"In the brain, laminin α2 is expressed by astrocyte foot processes at the glia limitans and blood-brain barrier"

This sentence summarizes prior CNS expression knowledge in the introduction to the human autopsy report.

Increased Cerebral White Matter Water Content

MR spectroscopy and diffusion imaging in nine children with merosin-deficient CMD support increased free water in affected cerebral white matter. A leaky perivascular basement membrane is a proposed upstream explanation; the MRI signal alone does not demonstrate demyelination. Human autopsy can show marked MRI abnormalities without white-matter histopathology.

cerebral hemisphere white matter UBERON:0002437

Show evidence (1 reference)

PMID:15703311 SUPPORT Human Clinical

"ADC mapping and (1)H MR spectroscopy reveal abnormally high free-water concentrations in the WM of patients with merosin-deficient CMD."

Direct human MR measurements in nine children support increased white-matter water content.

Pial Basement Membrane Assembly Failure

In a minority of patients the pial basement membrane is not merely thinner but focally breached. Autopsy of an MDC1A brain showed focal disruptions of the glia limitans with abnormal cortical lamination and arrested cerebellar granule cell migration, the classic substrate of a cobblestone malformation, here arising from loss of a structural laminin rather than from defective dystroglycan glycosylation. The module conformance is exact in mechanism: this entry substitutes an absent laminin ligand where the dystroglycanopathies substitute an unglycosylated receptor, and both converge on the same boundary failure.

pial basement membrane assembly GO:0070831 ↓ DECREASED

Downstream

Aberrant Cortical Neuronal Migration A breached glia limitans permits neurons and glia to overmigrate past the cortical surface, producing the cobblestone and polymicrogyric cortex.

Show evidence (1 reference)

PMID:32827036 SUPPORT Human Clinical

"Brain histopathology included focal disruptions of the glia limitans associated with abnormal cerebral cortical lamination or arrested cerebellar granule cell migration."

Directly demonstrates the pial boundary breach and its migration consequence in human MDC1A neuropathology.

Aberrant Cortical Neuronal Migration

Loss of pial boundary integrity permits abnormal cortical neuronal migration and lamination. Human pathology supports this route to cobblestone malformation and related cortical abnormalities. The authors propose that such abnormalities can underlie seizures or intellectual disability in a subset, but one autopsied patient had normal cognition and no seizures despite cobblestone pathology. Seizures also occur without a visible cortical anomaly.

Downstream

Seizures Disordered cortical migration and lamination can contribute to this clinical outcome; risk is variable and the intermediate circuit changes are not established.

Intellectual disability Disordered cortical migration and lamination can contribute to this clinical outcome; risk is variable and the intermediate circuit changes are not established.

Cobblestone cortical malformation Overmigration through focal glia-limitans breaches creates abnormal cortical lamination.

Polymicrogyria Abnormal cortical migration and organization can produce polymicrogyric patterns, which can overlap radiologically with cobblestone malformation.

Show evidence (2 references)

PMID:32827036 SUPPORT Other

"In MDC1A, the loss of laminin α2 leads to loss of integrity of the glia limitans BM and over-migration of neurons through glia limitans defects in the cerebral cortex or failed migration of granule cell neurons in the cerebellum."

The authors interpret human histology in terms of boundary failure and abnormal neuronal migration.

PMID:32827036 SUPPORT Human Clinical

"Brain histopathology included focal disruptions of the glia limitans associated with abnormal cerebral cortical lamination or arrested cerebellar granule cell migration."

Directly demonstrates the pial boundary breach and its migration consequence in human MDC1A neuropathology.

Loss of Myocardial Laminin-211 Support

Mechanism confidence: Provisional

Laminin-211 is a myocardial extracellular-matrix component. Its deficiency is a proposed contributor to the ventricular dysfunction observed in some patients, but cardiac model phenotypes vary and the human pathway has not been directly established.

Downstream

Abnormal left ventricular function Loss of myocardial matrix support is a proposed contributor to ventricular dysfunction; the relevant cellular intermediates and penetrance remain uncertain.

Show evidence (1 reference)

PMID:31308722 SUPPORT Other

"As laminin-211 is a major component of the myocardial ECM, it is likely that its loss will have important implications for cardiac physiology."

The review proposes a myocardial ECM mechanism; the intermediate cause of human ventricular dysfunction remains uncertain.

Impaired Respiratory Secretion Clearance

Weak cough impairs airway secretion clearance and predisposes to recurrent chest infection. This route is distinct from aspiration-related infection.

Downstream

Recurrent respiratory infections Retained airway secretions increase the risk of recurrent infection.

Show evidence (1 reference)

url:https://www.ncbi.nlm.nih.gov/books/NBK97333/ SUPPORT Other

"Poor secretion clearance resulting from weak cough leads to recurrent chest infection."

The clinical chapter explicitly establishes impaired cough-mediated clearance as a cause of recurrent infection.

⬡

Pathograph

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

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Phenotypes

Cardiovascular 1

Abnormal left ventricular function OCCASIONAL HP:0005162

Show evidence (2 references)

PMID:37476021 SUPPORT Human Clinical

"Cardiac assessment revealed QRS fragmentation in 62%, abnormal left ventricular global longitudinal strain in 25%, and decreased left ventricular ejection fraction in 14% of patients."

Quantifies the cardiac findings that motivate this phenotype and its frequency band.

PMID:32910545 SUPPORT Human Clinical

"Mild persistent left ventricular dysfunction (atrial septum or inferior wall) was observed in three patients at age 9, 14 and 19 years, respectively."

This isolates ventricular dysfunction from the combined count of all cardiac abnormalities.

Digestive 3

Feeding difficulties FREQUENT HP:0011968

Sequelae: Failure to thrive

Show evidence (2 references)

PMID:22675738 SUPPORT Other

"As disease progresses, facial muscle weakness, temporomandibular joint contractures, and macroglossia may further impair feeding and can affect speech."

States the mechanisms that aggravate feeding difficulty over the course of the disease.

PMID:32910545 SUPPORT Human Clinical

"Nineteen CD and one PD patient required gastrostomy insertion for failure to thrive and/or unsafe swallow (median age 10.9 years)."

The quoted 10.9 years is a time-to-event estimate; the observed median gastrostomy age was five years. Gastrostomy requirement does not measure all feeding impairment.

Gastroesophageal reflux HP:0002020

Sequelae: Aspiration

Show evidence (1 reference)

PMID:10332004 SUPPORT Human Clinical

"Six of eight children who had pH monitoring also had gastro-oesophageal reflux."

Six of eight selected tested children had reflux; this is not a denominator for all MDC1A patients.

Oropharyngeal dysphagia Oral-pharyngeal dysphagia HP:0200136

Sequelae: Aspiration Recurrent respiratory infections Failure to thrive

Show evidence (2 references)

PMID:10332004 SUPPORT Human Clinical

"Nine had an abnormal pharyngeal phase, with a delayed swallow reflex."

Videofluoroscopy directly demonstrates pharyngeal swallowing impairment in the selected severe cohort.

PMID:10332004 SUPPORT Human Clinical

"The others all had an abnormal oral phase (breakdown and manipulation of food and transfer to oropharynx)."

Thirteen of fourteen severely affected children had an abnormal oral phase on videofluoroscopy; the preceding sentence identifies the youngest child as the only normal study.

Eye 1

Ophthalmoparesis FREQUENT HP:0000597

Show evidence (2 references)

PMID:32910545 SUPPORT Human Clinical

"Facial weakness and ophtalmoparesis were observed in 21 and 18 CD patients, respectively, but in no PD."

Direct complete-deficiency cohort evidence supports partial ocular paresis and the FREQUENT band.

PMID:32848593 SUPPORT Other

"A progressive limitation of extraocular movements, in particular of upward gaze, is noted as early as at 2 years of age, with clear ophthalmoparesis in the horizontal and upwards direction becoming more evident by the end of the first decade."

The review describes progression and onset in childhood.

Head and Neck 6

Macroglossia HP:0000158

Sequelae: Feeding difficulties Oropharyngeal dysphagia

Show evidence (1 reference)

PMID:37476021 SUPPORT Human Clinical

"Seven of 27 patients had a macroglossia, a high arched palate was found in 17/27 patients, while 13/27 patients had an elongated face."

The direct cohort observation replaces an introductory review statement; the sample spans the broader LAMA2 spectrum.

Facial muscle weakness Weakness of facial musculature HP:0030319

Sequelae: Feeding difficulties Oropharyngeal dysphagia

Show evidence (1 reference)

PMID:32910545 SUPPORT Human Clinical

"Facial weakness and ophtalmoparesis were observed in 21 and 18 CD patients, respectively, but in no PD."

Facial weakness was observed in 21 of 42 complete-deficiency UK patients, distinct from the 18 with ophthalmoparesis. No facial weakness was reported in the four partial-deficiency patients; no disease-wide frequency is inferred.

Impaired mastication HP:0005216

Sequelae: Feeding difficulties

Show evidence (1 reference)

PMID:34281576 SUPPORT Human Clinical

"In LAMA2-CMD patients over two years old, feeding problems such as chewing difficulty (58.9%, 53/90) and swallowing difficulty (12.2%, 11/90) were common."

Uses the internally consistent results sentence instead of erroneous table percentages.

Neck rigidity Stiff neck HP:0025258

Show evidence (1 reference)

PMID:32910545 SUPPORT Human Clinical

"Neck rigidity was reported in 21 patients (20 CD and one PD), spine rigidity in 15 (13 CD and two PD), and lordosis in 12 (10 CD and two PD)."

The UK cohort separates neck, spine and lordosis findings and complete from partial deficiency.

Enlarged cisterna magna HP:0002280

Show evidence (1 reference)

PMID:39213089 SUPPORT Human Clinical

"Furthermore, nine of the 12 reevaluated patients had structural abnormalities of the brainstem-vermis angle: four patients had a Blake’s pouch cyst, one of whom needed a ventriculo-peritoneal shunt; and five patients had a megacisterna magna (brainstem-vermis-angle 10–18°)[44]."

The results distinguish four Blake pouch cysts from five enlarged cisterna magna findings in a selected imaging subset.

Blake pouch cyst Blake's pouch cyst HP:0033140

Sequelae: Hydrocephalus

Show evidence (1 reference)

PMID:39213089 SUPPORT Human Clinical

The results distinguish four Blake pouch cysts from five enlarged cisterna magna findings in a selected imaging subset.

Immune 1

Recurrent respiratory infections FREQUENT HP:0002205

Show evidence (3 references)

PMID:22675738 SUPPORT Other

"Failure to thrive, gastroesophageal reflux, aspiration, and recurrent chest infections necessitating frequent hospitalizations are common."

GeneReviews names recurrent chest infection as a common complication.

PMID:34281576 SUPPORT Human Clinical

"Twenty-four LAMA2-related muscular dystrophy patients died, mostly due to severe pneumonia."

Establishes pneumonia as the dominant cause of death.

PMID:34281576 SUPPORT Human Clinical

"In total, 58.9% (63/107) of LAMA2-CMD and 35.7% (5/14) of LGMDR23 patients had a history of recurrent respiratory infection, mainly at ages of 0–3 years and 6–15 years (Fig."

Recurrent respiratory infection was recorded in 63/107 clinical LAMA2-CMD patients; the broader cohort includes a separately reported LGMDR23 group.

Limbs 6

Elbow flexion contracture HP:0002987

Show evidence (2 references)

PMID:39213089 SUPPORT Human Clinical

"Descriptions of joint contractures based on the neurological examination (yes/no without further grading) were recorded in the CRF and were available for 18 patients and most frequently observed in the elbow (N = 10), hip (N = 9), long finger flexors (N = 12), knee (N = 13) and ankle (N = 13) (Fig. 1)."

Elbow contractures were recorded in 10/18 Swiss participants: 14 never walked and four had attained walking. This mixed, age-variable LAMA2 cohort is not a congenital-only frequency estimate. The Swiss observation does not specify flexion direction; UK goniometry below supplies that specificity.

PMID:32910545 SUPPORT Human Clinical

"We observed a linear increase in elbow flexor contractures in CD subjects."

UK longitudinal data directly establish flexion specificity and progression.

Knee flexion contracture HP:0006380

Show evidence (2 references)

PMID:39213089 SUPPORT Human Clinical

Knee contractures were recorded in 13/18 Swiss participants: 14 never walked and four had attained walking. This mixed, age-variable LAMA2 cohort is not a congenital-only frequency estimate. The Swiss observation does not specify flexion direction; UK goniometry below supplies that specificity.

PMID:32910545 SUPPORT Human Clinical

"The following longitudinally collected variables were considered: weight, current motor ability, goniometry measurements of right hip flexion, knee flexion and elbow flexion, scoliosis (defined as Cobb Angle >20°), respiratory complications, spirometry measurements (Forced Vital Capacity..."

Methods identify the flexion directions measured; the Swiss clinical observation independently establishes contractures at these joints.

Hip flexion contracture HP:0020025

Show evidence (2 references)

PMID:39213089 SUPPORT Human Clinical

Hip contractures were recorded in 9/18 Swiss participants: 14 never walked and four had attained walking. This mixed, age-variable LAMA2 cohort is not a congenital-only frequency estimate. The Swiss observation does not specify flexion direction; UK goniometry below supplies that specificity.

PMID:32910545 SUPPORT Human Clinical

Methods identify the flexion directions measured; the Swiss clinical observation independently establishes contractures at these joints.

Ankle contracture HP:0034677

Show evidence (1 reference)

PMID:39213089 SUPPORT Human Clinical

Ankle contractures were recorded in 13/18 Swiss participants: 14 never walked and four had attained walking. This mixed, age-variable LAMA2 cohort is not a congenital-only frequency estimate. The source does not specify a fixed ankle position or grade contracture severity.

Finger flexion contracture Flexion contracture of finger HP:0012785

Show evidence (1 reference)

PMID:32910545 SUPPORT Human Clinical

"Long finger flexor contractures were reported in 30/42 (71%) CD patients as well as 2/4 PD patients."

Direct anatomical and subgroup-specific observation.

Hip dislocation HP:0002827

Show evidence (1 reference)

PMID:32910545 SUPPORT Human Clinical

"Hip dislocation was reported in 12 CD and two PD patients, pectus excavatum in two CD and pectus carinatum in two CD patient."

Directly records these structural findings in the UK cohort without establishing their individual mechanisms.

Metabolism 1

Elevated serum creatine kinase VERY_FREQUENT Elevated circulating creatine kinase activity HP:0003236

Show evidence (2 references)

PMID:32848593 SUPPORT Other

"Clinical hallmarks are early-onset severe hypotonia, axial weakness, inability to achieve independent ambulation, and elevated creatine kinase (CK) levels, commonly >1,000 IU/L"

Gives the characteristic magnitude of the creatine kinase elevation.

PMID:39213089 SUPPORT Human Clinical

"CK level was available for 13 patients and was elevated in all of them"

Records universal elevation in the registry cohort, supporting the VERY_FREQUENT band.

Musculoskeletal 13

Neonatal hypotonia HP:0001319

Show evidence (1 reference)

PMID:22675738 SUPPORT Other

"MDC1A is typically characterized by neonatal profound hypotonia, poor spontaneous movements, and respiratory failure."

GeneReviews names neonatal profound hypotonia as a defining manifestation.

Axial muscle weakness VERY_FREQUENT HP:0003327

Sequelae: Inability to walk Delayed gross motor development Hyperlordosis

Show evidence (2 references)

PMID:37476021 SUPPORT Human Clinical

"Axial and proximal muscle weakness was most pronounced."

States the weakness distribution directly.

PMID:32848593 SUPPORT Other

"Clinical hallmarks are early-onset severe hypotonia, axial weakness, inability to achieve independent ambulation, and elevated creatine kinase (CK) levels, commonly >1,000 IU/L"

Lists axial weakness among the defining clinical hallmarks.

Joint contracture VERY_FREQUENT Flexion contracture HP:0001371

Sequelae: Inability to walk Motor regression

Show evidence (2 references)

PMID:32848593 SUPPORT Other

"Progressive joint contractures, respiratory insufficiency, and scoliosis are observed in almost all patients."

Supports the VERY_FREQUENT band for contractures.

PMID:39213089 SUPPORT Human Clinical

"In four patients with CMD, contractures were reported as the initially presenting symptom."

Documents contracture as a presenting rather than late feature.

Spinal rigidity HP:0003306

Show evidence (1 reference)

PMID:32910545 SUPPORT Human Clinical

"Neck rigidity was reported in 21 patients (20 CD and one PD), spine rigidity in 15 (13 CD and two PD), and lordosis in 12 (10 CD and two PD)."

The UK cohort separates neck, spine and lordosis findings and complete from partial deficiency.

Scoliosis FREQUENT HP:0002650

Sequelae: Respiratory insufficiency due to muscle weakness

Show evidence (1 reference)

PMID:32910545 SUPPORT Human Clinical

"Thirty-two CD and one PD patient developed scoliosis, nine underwent spinal surgery."

The abstract reports 32/42 complete-deficiency patients, while the results report 33/42; this internal discrepancy is retained explicitly rather than silently resolved.

Increased endomysial connective tissue HP:0100297

Show evidence (1 reference)

PMID:7550355 SUPPORT Other

"Histological changes seen in muscle biopsies consist of large variations in muscle fibre size, a few necrotic and regenerating fibres and a marked increase in endomysial collagen tissue."

This introductory description summarizes congenital muscular dystrophy histology; it does not provide an MDC1A-specific biopsy prevalence.

Pathologic fractures HP:0002756

Show evidence (1 reference)

PMID:37476021 SUPPORT Human Clinical

"Eleven patients had experienced 1 or more fragility long bone fractures."

The observed phenotype is fragility fracture, not necessarily recurrent fracture.

Proximal muscle weakness HP:0003701

Sequelae: Inability to walk Delayed gross motor development

Show evidence (1 reference)

PMID:32910545 SUPPORT Human Clinical

"The distribution of limb weakness followed a proximodistal gradient in both CD and PD patients."

Separately records the proximal component of the previously bundled weakness phenotype.

Respiratory insufficiency due to muscle weakness HP:0002747

Show evidence (1 reference)

PMID:32848593 SUPPORT Other

"Progressive, restrictive pulmonary insufficiency due to weakness of intercostal and accessory muscles is the most common cause of morbidity and mortality in LAMA2-RD."

Clinical review explicitly attributes restrictive insufficiency to respiratory muscle weakness.

Hyperlordosis HP:0003307

Sequelae: Oropharyngeal dysphagia Scoliosis

Show evidence (1 reference)

PMID:32910545 SUPPORT Human Clinical

"Neck rigidity was reported in 21 patients (20 CD and one PD), spine rigidity in 15 (13 CD and two PD), and lordosis in 12 (10 CD and two PD)."

The UK cohort separates neck, spine and lordosis findings and complete from partial deficiency.

Pectus excavatum HP:0000767

Show evidence (1 reference)

PMID:32910545 SUPPORT Human Clinical

"Hip dislocation was reported in 12 CD and two PD patients, pectus excavatum in two CD and pectus carinatum in two CD patient."

Directly records these structural findings in the UK cohort without establishing their individual mechanisms.

Pectus carinatum HP:0000768

Show evidence (1 reference)

PMID:32910545 SUPPORT Human Clinical

"Hip dislocation was reported in 12 CD and two PD patients, pectus excavatum in two CD and pectus carinatum in two CD patient."

Directly records these structural findings in the UK cohort without establishing their individual mechanisms.

Reduced bone mineral density HP:0004349

Sequelae: Pathologic fractures

Show evidence (1 reference)

PMID:37476021 SUPPORT Human Clinical

"The femoral mineral bone density was reduced in all adults (t score: −2.6 ± 1.4) and in 7 of 10 pediatric patients (z score: −3.5 ± 1.8)."

Direct densitometry in the broader LAMA2 spectrum, not a severe congenital-only estimate.

Nervous System 11

Inability to walk VERY_FREQUENT HP:0002540

Show evidence (2 references)

PMID:34281576 SUPPORT Human Clinical

"Head control, independent sitting and ambulation were achieved in 76.3%, 92.6% and 18.4% of LAMA2-CMD patients at median ages of 6.0 months (range 2.0-36.0 months), 11.0 months (range 6.0-36.0 months), and 27.0 months (range 18.0-84.0 months), respectively."

The walking denominator is 98 clinical LAMA2-CMD patients older than 18 months, not all 116 CMD patients or an immunostaining-defined complete-deficiency group.

PMID:32910545 SUPPORT Human Clinical

"One CD and two PD subjects achieved independent ambulation."

One of 42 patients classified as completely deficient attained independent walking; classification was not based on biopsy in every participant.

Delayed gross motor development VERY_FREQUENT HP:0002194

Show evidence (1 reference)

PMID:32910545 SUPPORT Human Clinical

"All patients had motor delay."

Direct observation in the UK cohort of 42 complete- and four partial-deficiency patients.

Hyperintensity of cerebral white matter on MRI VERY_FREQUENT HP:0030890

Show evidence (2 references)

PMID:32848593 SUPPORT Other

"Characteristic brain white matter (WM) hypointensity on T1 magnetic resonance imaging (MRI), and increased T2 signal in the periventricular and subcortical WM, are invariably observed in most patients older than 6 months"

Establishes the imaging finding and its near-universal presence beyond six months, supporting the VERY_FREQUENT band.

PMID:39213089 SUPPORT Human Clinical

"The youngest age at which MRI showed clear white matter changes was 3 months."

Records the earliest age at which the finding was demonstrable in this cohort.

Cobblestone cortical malformation Type II lissencephaly HP:0007260

Show evidence (2 references)

PMID:39213089 SUPPORT Human Clinical

"In 7 patients, additional cortical abnormalities were found: parieto-occipital cobblestone malformation (six patients) and/or polymicrogyria (three patients)."

Documents the cobblestone malformation and its parieto-occipital distribution.

PMID:32827036 SUPPORT Human Clinical

"These cases demonstrate that cobblestone malformation may be an important manifestation of the brain pathology in MDC1A and can be present even when patients have a structurally normal brain MRI."

Selected human cases show that clinical MRI can miss subtle cobblestone pathology, without quantifying its frequency in unselected MDC1A.

Polymicrogyria HP:0002126

Show evidence (2 references)

PMID:37182895 SUPPORT Human Clinical

"10 patients (19.2%) presented with cortical malformations (polymicrogyria, lissencephaly-pachygyria, and cobblestone)"

This establishes polymicrogyria within the observed cortical abnormalities; 10/52 is the aggregate malformation count and cannot serve as polymicrogyria prevalence.

PMID:18406646 SUPPORT Human Clinical

"When 6.9 years old, she developed focal occipital seizures and absence-like status when awake, with probable relation to an extensive bilateral occipital micropolygyria."

Documents occipital polymicrogyria with focal seizures in a patient with a homozygous LAMA2 stop-codon variant.

Seizures OCCASIONAL HP:0001250

Show evidence (2 references)

PMID:34281576 SUPPORT Human Clinical

"Seizures occurred in 35.7% of LGMDR23 and 9.5% of LAMA2-CMD patients."

The stated seizure percentages include febrile seizures as well as epilepsy and refer to clinical onset subgroups.

PMID:32848593 SUPPORT Other

"Seizures, usually responsive to antiepileptic medications in the absence of an underlying cortical anomaly, are observed in up to ~30% of patients"

Gives the upper bound of reported frequency and the response to first-line treatment.

Intellectual disability OCCASIONAL HP:0001249

Show evidence (2 references)

PMID:37182895 SUPPORT Human Clinical

"10 patients (19.2%) presented with cortical malformations (polymicrogyria, lissencephaly-pachygyria, and cobblestone),10 patients (19.2%) presented with epilepsy, and 8 (15.4%) had intellectual disability."

The 52-patient cohort includes both severe and ambulant phenotypes; this is not a severe-only denominator.

PMID:39213089 SUPPORT Other

"Usually, cognitive abilities of patients are in the normal range"

Establishes that normal cognition is the rule, which is why this phenotype is banded as occasional rather than frequent.

Decreased motor nerve conduction velocity FREQUENT HP:0003431

Show evidence (3 references)

PMID:8576559 SUPPORT Human Clinical

"All but two of the 10 merosin-deficient cases had reduced motor nerve conduction, whereas all the merosin-positive cases had normal results."

Gives the frequency and the specificity of the finding to merosin deficiency.

PMID:8576559 SUPPORT Human Clinical

"Sensory nerve studies showed no difference between the two groups."

Supports the motor-predominant electrophysiological picture described here.

PMID:32910545 SUPPORT Human Clinical

"Six out of 13 CD patients showed mildly reduced conduction velocities for age (in ulnar or peroneal motor nerves)."

The later tested UK subgroup supports variable motor conduction slowing, rather than universal neuropathy.

Pontine hypoplasia Hypoplasia of the pons HP:0012110

Show evidence (1 reference)

PMID:39213089 SUPPORT Human Clinical

"In ten of the 12 reevaluated MRIs we found pontine hypoplasia, as well as four with a large interthalamic adhesion."

Direct MRI observation; a specific developmental causal pathway was not established.

Hydrocephalus HP:0000238

Show evidence (1 reference)

PMID:39213089 SUPPORT Human Clinical

"Although, to our knowledge, not previously reported, we observed the frequent occurrence of a large tegmento-vermian angle (9/12) classified as megacisterna magna or Blake’s pouch cyst (3/12), causing a hydrocephalus and requiring a ventriculoperitoneal shunt in one patient."

The discussion explicitly attributes hydrocephalus to the posterior-fossa cyst abnormality; its aggregate cyst count differs from the results.

Motor regression HP:0033044

Show evidence (1 reference)

PMID:34281576 SUPPORT Human Clinical

"Motor regression in LAMA2-CMD mainly occurred concurrently with rapid progression of contractures during 6-9 years old."

The clinical temporal association does not by itself prove that contractures account for every lost skill.

Respiratory 2

Restrictive ventilatory defect VERY_FREQUENT HP:0002091

Show evidence (2 references)

PMID:37476021 SUPPORT Human Clinical

"Respiratory function was impaired in 85% of patients without prominent diaphragm dysfunction and was independent of age."

Gives the 85% frequency supporting the VERY_FREQUENT band and the absence of diaphragmatic predominance.

PMID:32910545 SUPPORT Human Clinical

"Twenty-two CD required nocturnal noninvasive ventilation (median age 11.7 years)."

Documents the ventilatory support requirement and its timing.

Aspiration HP:0002835

Sequelae: Recurrent respiratory infections

Show evidence (1 reference)

PMID:10332004 SUPPORT Human Clinical

"Three of these also showed pooling of food in the larynx and three showed frank aspiration."

Direct swallowing-study finding; the selected testing denominator is not a population frequency.

Voice 1

Weak cry HP:0001612

Show evidence (1 reference)

PMID:34281576 SUPPORT Human Clinical

"The onset symptoms in LAMA2-CMD were variable combinations of severe muscle weakness (n = 114), hypotonia (n = 114), weak cry (n = 48), neonatal feeding difficulty (n = 30), neonatal respiratory difficulty (n = 9)."

Direct congenital-cohort presenting symptom.

Growth 1

Failure to thrive HP:0001508

Show evidence (2 references)

PMID:10332004 SUPPORT Human Clinical

"Twelve of the 14 children were below the 3rd centile for weight."

Documents poor growth in a selected severe pediatric feeding study, not a population prevalence.

PMID:10332004 SUPPORT Human Clinical

"As a result of the study five children had a gastrostomy, which stopped the chest infections and improved weight gain."

Within-series improvement supports feeding-related morbidity; it is not a controlled treatment effect.

🧬

Genetic Associations

LAMA2

Gene: LAMA2 hgnc:6482 relationship_type: CAUSATIVE

Show evidence (6 references)

PMID:7550355 SUPPORT Human Clinical

The report that established LAMA2 as the causal gene.

PMID:34281576 SUPPORT Human Clinical

"The top three high-frequency disease-causing variants in Han Chinese patients were c.7147C > T (p.R2383*), exon 4 deletion, and c.5156_5159del (p.K1719Rfs*5)."

Records the recurrent Han Chinese alleles. Population-specific recurrence matters for testing strategy - a targeted assay is only worth building where an allele actually recurs.

PMID:34281576 SUPPORT Human Clinical

"Copy number variations were identified in 26.4% of survivors and 50.0% of nonsurvivors, suggesting that copy number variations were associated with lower rate of survival (p = 0.029)."

The one prognostic genetic association in this disease rather than a merely descriptive one: copy-number variants are over-represented among non-survivors. Quoted with the authors' own hedge ("suggesting") intact - it is a single-cohort association at p = 0.029, not an established rule.

+ 3 more references

💊

Medical Actions

Multidisciplinary Supportive Care

Action: multidisciplinary supportive care Ontology label: Supportive Care NCIT:C15747

Platform: Behavioral / lifestyle

There is no disease-modifying therapy, so management is anticipatory surveillance plus intervention at defined thresholds, delivered by a coordinated team. The surveillance list is long because the complications are: nutrition and swallow safety, neurologic status, pulmonary function, cognition and education, mobility, cardiac rhythm and function, vision, and bone quality. The life-span cohort authors recommend ECG, Holter monitoring and echocardiography, recurrent bone mineral density assessment, and vitamin D/calcium supplementation. These are surveillance and supportive-care recommendations, not measured disease-modifying treatment effects.

Show evidence (3 references)

PMID:22675738 SUPPORT Other

"It is recommended that multidisciplinary care be provided by specialists in neurology, gastroenterology, nutrition, orthopedics, occupational and physical therapy, speech and language therapy, education, psychiatry, pulmonary medicine, cardiology, ophthalmology, and social work."

GeneReviews states the multidisciplinary management recommendation this treatment records.

PMID:37476021 SUPPORT Other

"We advise cardiac surveillance by regular screening of patients with ECG, Holter monitor, and echocardiography with advanced techniques for early detection and treatment of cardiac manifestations."

The authors recommend cardiac screening after their mixed-age LAMA2 cohort assessment. This is clinical guidance, not a trial demonstrating surveillance efficacy.

PMID:37476021 SUPPORT Other

"Based on the low bone quality, we further recommend recurrent bone mineral density assessment and optimization of bone quality through vitamin D and calcium suppletion."

The recommendation follows cohort densitometry and fragility-fracture findings. The study did not test supplementation as a disease-modifying treatment or determine a congenital-only screening interval.

Non-Invasive Ventilation

Action: nocturnal non-invasive ventilation Ontology label: Non-Invasive Mechanical Ventilation NCIT:C171457

Platform: Device

Nocturnal non-invasive ventilation for restrictive respiratory failure, started at a median of around twelve years in the complete-deficiency form. Long-term invasive ventilation or tracheostomy is uncommon in paediatric practice; invasive support is generally reserved for short periods during intercurrent infection.

Mechanism Target:

BYPASSES Respiratory Muscle Weakness and Reduced Chest Wall Compliance — Ventilatory support substitutes for the failing respiratory pump rather than acting on the muscle lesion, and it does not slow the decline in vital capacity.

Show evidence (2 references)

PMID:32910545 SUPPORT Human Clinical

"Twenty-two CD required nocturnal noninvasive ventilation (median age 11.7 years)."

Documents the use and timing of nocturnal non-invasive ventilation in this population.

PMID:32848593 SUPPORT Other

"While invasive ventilation might become necessary for short periods and typically during times of respiratory infections, long-term use of invasive ventilation or use of ventilation via a tracheostomy is rare in pediatric LAMA2-RD patients."

Supports the preference for non-invasive over invasive long-term support.

Gastrostomy Feeding

Action: gastrostomy tube placement Ontology label: Gastrostomy Tube Procedure NCIT:C157864

Platform: Surgery

Gastrostomy supports nutrition when oral intake is inadequate or swallowing is unsafe. Nineteen complete-deficiency and one partial-deficiency UK patients received a tube; the observed median age was five years, versus a 10.9-year time-to-event estimate. A selected feeding series reported improved weight gain and fewer chest infections after placement. Tube feeding does not guarantee normal growth or eliminate all aspiration risk.

Show evidence (2 references)

PMID:32910545 SUPPORT Human Clinical

"Nineteen CD and one PD patient required gastrostomy insertion for failure to thrive and/or unsafe swallow (median age 10.9 years)."

The quoted 10.9 years is a time-to-event estimate; the observed median gastrostomy age was five years. Gastrostomy requirement does not measure all feeding impairment.

PMID:10332004 SUPPORT Human Clinical

"As a result of the study five children had a gastrostomy, which stopped the chest infections and improved weight gain."

Within-series improvement supports feeding-related morbidity; it is not a controlled treatment effect.

Physical Therapy and Contracture Management

Action: physical therapy Ontology label: Physical Therapy NCIT:C15302

Platform: Behavioral / lifestyle

Stretching, splinting, orthoses and positioning to slow contracture and preserve what function exists. Given that contracture is driven by early fibrogenesis and accumulates linearly, this is a rate-limiting intervention rather than a preventive one.

Mechanism Target:

MODULATES Endomysial Fibrosis and Replacement of Muscle — Mechanical stretching opposes the shortening produced by fibrotic replacement without addressing the matrix deposition itself.

Show evidence (1 reference)

PMID:22675738 SUPPORT Other

GeneReviews includes physical and occupational therapy in the recommended management team.

Scoliosis Surgery

Action: spinal fusion for neuromuscular scoliosis Ontology label: Spinal Fusion NCIT:C157986

Platform: Surgery

Posterior spinal instrumentation and fusion for progressive scoliosis, needed by a substantial minority of non-ambulant patients: nine of 33 with scoliosis in one cohort and five of ten in another. It is a seating and comfort intervention as much as a respiratory one.

Show evidence (2 references)

PMID:32910545 SUPPORT Human Clinical

"Thirty-two CD and one PD patient developed scoliosis, nine underwent spinal surgery."

Gives the proportion of scoliotic patients proceeding to surgery.

PMID:39213089 SUPPORT Human Clinical

"In our cohort five out of ten patients with CMD needed a surgical intervention for their severe scoliosis."

Independent cohort corroboration of the surgical rate.

Antiepileptic Drug Therapy

Action: antiepileptic drug therapy Ontology label: Anticonvulsant Therapy NCIT:C64172

Agent: anticonvulsant agent NCIT:C264

Platform: Small molecule

Seizures in this disease are usually controlled with first-line antiepileptic drugs where there is no underlying cortical anomaly. Where a cortical malformation is present, drug resistance is reported, so the imaging finding has direct therapeutic implications.

Show evidence (2 references)

PMID:32848593 SUPPORT Other

"Epilepsy should be monitored for and usually can be controlled with first-line antiepileptic drugs."

States the recommendation and the expected response.

PMID:39213089 SUPPORT Human Clinical

"One had continuous spike-waves during sleep (CSWS) and one had drug-resistant frequent focal seizures with impaired awareness (cortical malformation in one patient)."

Documents the drug-resistant subgroup associated with cortical malformation.

Genetic Counseling

Action: genetic counseling Ontology label: Genetic Counseling NCIT:C15240

Platform: Behavioral / lifestyle

Autosomal recessive counselling with a 25% recurrence risk per pregnancy. Once the familial variants are known, carrier testing, prenatal and preimplantation genetic testing become available, which matters in a disease with no treatment and a severe natural history.

Show evidence (1 reference)

PMID:22675738 SUPPORT Other

"Once the LAMA2 pathogenic variants have been identified in an affected family member, carrier testing for at-risk relatives and prenatal and preimplantation genetic testing are possible."

States the reproductive options this counselling delivers.

Omigapil

Action: Pharmacotherapy NCIT:C15986

Agent: omigapil NCIT:C97362

Platform: Small molecule

An anti-apoptotic small molecule that inhibits the GAPDH-Siah1-mediated death pathway. It is the only therapeutic small molecule to have reached a clinical trial in this disease. In dyW and dy2J mice it inhibits muscle apoptosis, reduces weight loss and skeletal deformity, increases locomotor activity and delays mortality. The human study (CALLISTO, NCT01805024) was a phase 1 open-label pharmacokinetic and safety study over twelve weeks in 20 patients with LAMA2- or COL6-related dystrophy; it met its primary endpoint, but it was neither designed nor powered to show clinical benefit, and none was observed. This is an unapproved investigational agent and is recorded here as the state of the therapeutic pipeline, not as available care.

Mechanism Target:

INHIBITS Myofibre Degeneration, Necrosis and Apoptosis — Inhibiting GAPDH-Siah1-mediated apoptosis reduces myofibre death in the mouse. Whether this translates to humans is unresolved: the only human trial was a pharmacokinetic study.

Show evidence (1 reference)

PMID:19759319 SUPPORT Model Organism

"Specifically, we demonstrate that treatment with omigapil inhibits apoptosis in muscle, reduces body weight loss and skeletal deformation, increases locomotive activity, and protects from early mortality."

Demonstrates the anti-apoptotic effect on the target node and the downstream functional benefit in the mouse.

Show evidence (3 references)

PMID:19759319 SUPPORT Model Organism

"Here we demonstrate that the proapoptotic glyceraldehyde-3-phosphate dehydrogenase (GAPDH)-Siah1-CBP/p300-p53 pathway is activated in a mouse model for MDC1A."

Establishes that the pathway omigapil inhibits is actually engaged in the disease model.

PMID:38915423 SUPPORT Human Clinical

"In general, omigapil was safe and well tolerated."

The safety result of the only human trial.

PMID:38915423 NO_EVIDENCE Human Clinical

"No consistent changes were seen in the disease-relevant clinical assessments during the duration of the study."

The small phase 1 safety/pharmacokinetic study was not designed to establish efficacy; absence of consistent clinical change is not evidence of a definitive lack of treatment benefit.

Avoidance of Succinylcholine and Statins

Action: avoidance of contraindicated agents Ontology label: Supportive Care NCIT:C15747

A drug-safety measure rather than a therapy, and the one item on this list that changes management in an emergency department. Succinylcholine during anaesthetic induction risks hyperkalaemia and cardiac conduction abnormalities in this population; statins risk further muscle damage. Both should be recorded on an alert document.

Show evidence (1 reference)

PMID:22675738 SUPPORT Other

"Succinylcholine in induction of anesthesia because of risk of hyperkalemia and cardiac conduction abnormalities; statins, cholesterol-lowering medications, because of the risk of muscle damage."

The GeneReviews Agents/Circumstances to Avoid list, quoted verbatim.

🔬

Diagnosis

LAMA2 molecular genetic testing (PRESENT)

Identification of biallelic pathogenic LAMA2 variants establishes the diagnosis. Next-generation sequencing has largely displaced the biopsy-first pathway, but copy-number analysis matters: single and multi-exon deletions account for a substantial minority of alleles and are missed by sequencing alone. Functional splice assessment can clarify suspected splice-altering variants: the Swiss cohort confirmed aberrant splicing for c.4960-17C>A. This variant-level evidence does not establish a universal RNA-sequencing workflow, preferred tissue, or diagnostic yield after single-allele detection.

Show evidence (3 references)

PMID:22675738 SUPPORT Other

States the molecular diagnostic criterion.

PMID:32848593 SUPPORT Other

"Next-generation sequencing (NGS) has greatly improved diagnostic abilities for LAMA2-RD, and the majority of patients with merosin deficiency carry recessive pathogenic variants in the LAMA2 gene."

Supports the primacy of sequencing in the current diagnostic pathway.

PMID:39213089 SUPPORT Human Clinical

"We confirmed aberrant splicing for the c.4960-17C > A variant (see Figure S1 and Table S1)."

The Swiss clinical study reports functional confirmation for a specific intronic variant. It supports an adjunctive splice assessment, not the broader report-proposed RNA sequencing or RT-PCR algorithm for every unresolved patient.

Muscle biopsy merosin immunostaining (PRESENT)

Absent or reduced laminin alpha-2 immunostaining on muscle, on a dystrophic background. It remains useful for grading complete versus partial deficiency, but the residual-protein reading is not reliable enough to predict phenotype in an individual patient, and skin biopsy can substitute where complete deficiency is suspected.

Show evidence (2 references)

PMID:39213089 SUPPORT Human Clinical

"However, the amount of merosin in muscle biopsy does not enable a clear prediction of clinical phenotype"

States the prognostic limitation of the immunostain that this entry records.

PMID:32848593 SUPPORT Other

"Absence of laminin alpha 2 at the epidermal and adnexal basement membranes and intradermal sensory nerves can be demonstrated in skin biopsies, particularly in cases of complete laminin alpha 2 deficiency"

Supports skin biopsy as an alternative demonstration of the protein deficiency.

Brain MRI white matter signal (PRESENT)

Diffuse periventricular and subcortical T2 hyperintensity is close to universal beyond six months and is often the finding that redirects an undiagnosed floppy infant towards LAMA2. Below six months it may be absent, so a normal early MRI does not exclude the diagnosis. Re-reading the MRI specifically for cortical malformation is worthwhile: it is frequently missed on the initial report.

Show evidence (2 references)

PMID:32848593 SUPPORT Other

Establishes the MRI finding and its age threshold.

PMID:37182895 SUPPORT Human Clinical

"shows the importance of reviewing the brain MRI of patients with LAMA2-RD"

Supports the recommendation to re-review the MRI for cortical malformation.

Motor nerve conduction study (PRESENT)

Slowed motor conduction supports merosin deficiency over other congenital muscular dystrophies. It is supportive rather than decisive: some cohorts report normal studies, and it is not needed once genetic testing is available.

Show evidence (2 references)

PMID:8576559 SUPPORT Human Clinical

"All but two of the 10 merosin-deficient cases had reduced motor nerve conduction, whereas all the merosin-positive cases had normal results."

Establishes the discriminating value of the study between merosin-deficient and merosin-positive congenital muscular dystrophy.

PMID:39213089 SUPPORT Human Clinical

"Electrophysiological nerve conduction studies were done in three patients (two with motor and sensory measurements, one patient with only sensory measurement) and were reported as being normal."

Records a cohort in which the studies were normal, which is why this test is described as supportive rather than decisive.

📈

Progression

Neonatal and infantile

Onset is at or within days of birth in three quarters of congenital-form patients: profound hypotonia, weak cry, poor spontaneous movement, sometimes neonatal feeding or respiratory difficulty. The mouse data suggest the pathology is already well established by this point, with apoptotic fibres from postnatal day 1 and full dystrophic architecture by day 4, which is the argument for intervening as early as diagnosis permits.

Show evidence (2 references)

PMID:34281576 SUPPORT Human Clinical

Enumerates the presenting features of this phase in a 116-patient congenital-form cohort.

PMID:31586140 SUPPORT Model Organism

"Therapeutic tests in the dy3K/dy3K mouse model should therefore be initiated shortly after birth, but should also take into account timing and correlation between regenerative and pathogenic events."

The authors' own inference about intervention timing from the perinatal onset of pathology.

Early and middle childhood

Motor milestones are attained late and incompletely: head control by about six months and independent sitting by about eleven months in most, but ambulation in fewer than a fifth. Contractures accumulate steadily and scoliosis appears in the non-ambulant, typically after six years. Motor regression, when it happens, clusters in the six-to-nine-year window and tracks the contracture phase rather than a separate loss of strength.

Show evidence (2 references)

PMID:34281576 SUPPORT Human Clinical

"Motor regression in LAMA2-CMD mainly occurred concurrently with rapid progression of contractures during 6-9 years old."

Times the regression window and links it to contracture progression.

PMID:32848593 SUPPORT Other

"Progressive scoliosis is common after 6 years of age, leading to a surgical correction in most patients."

Times the onset of scoliosis and its surgical burden to this phase.

Adolescence and respiratory decline

The dominant events of the second decade are respiratory and nutritional. Forced vital capacity falls at about 2.9% predicted per year, nocturnal non-invasive ventilation is started at a median of around twelve years, and gastrostomy at around eleven. Spinal surgery is common. Cardiac abnormalities, mostly subclinical, are increasingly detected.

Show evidence (2 references)

PMID:32910545 SUPPORT Human Clinical

"Twenty-two CD required nocturnal noninvasive ventilation (median age 11.7 years)."

Dates the ventilatory transition that defines this phase.

PMID:32910545 SUPPORT Human Clinical

"Nineteen CD and one PD patient required gastrostomy insertion for failure to thrive and/or unsafe swallow (median age 10.9 years)."

Dates the nutritional transition in the same cohort.

Survival and cause of death

Mortality is driven by respiratory infection rather than by cardiac or neurological disease. About 30% of early-onset patients die within the first decade in one review's summary; in a tertiary cohort seven of 42 complete-deficiency patients died at a median of 12 years, and in a 130-patient national cohort 24 died, mostly of severe pneumonia. Survival into adulthood is routine in the partial-deficiency subtype.

Show evidence (2 references)

PMID:31308722 SUPPORT Other

"The most common cause of death in early-onset LAMA2 MD is respiratory tract infection, with 30% of them dying within the first decade of life."

Gives both the leading cause of death and a first-decade mortality figure.

PMID:32910545 SUPPORT Human Clinical

"Seven CD patients died at median age 12 years."

Gives median age at death in a well-characterised complete-deficiency cohort.

📊

Prevalence

Worldwide, children

Point Prevalence 0.8 per 100,000 1–9 per 1,000,000

Reported as approximately 4 in 500,000 children, which normalises to 0.8 per 100,000. This is a review's summary figure rather than a registry count, and published estimates for LAMA2-related dystrophy as a whole span roughly an order of magnitude between countries, so the coarse band carries more weight than the point value.

Show evidence (1 reference)

PMID:31308722 SUPPORT Other

"LAMA2 MD is the most common congenital muscular dystrophy, affecting approximately 4 in 500,000 children."

Gives the population rate normalised into this record.

Switzerland, ages 0-23 years

Point Prevalence 0.8 per 100,000 1–9 per 1,000,000

A registry-denominator minimum rather than an ascertained rate: the numerator is patients enrolled in the Swiss Registry for Neuromuscular Disorders, so unenrolled cases are missed and the authors state the figure as a floor. It covers LAMA2-related dystrophy as a whole, of which the congenital severe form curated here was 14 of 18 patients.

Show evidence (1 reference)

PMID:39213089 SUPPORT Human Clinical

"Therefore, the prevalence of LAMA2-RD in Switzerland for the age group 0-23 years is at least 17/2 123 128 = 0.8 : 100 000."

States the registry-based minimum prevalence recorded here.

Congenital muscular dystrophy cohorts, worldwide

Unknown Rare

Share of the congenital muscular dystrophy population rather than a population rate. Recorded because it is the figure most often quoted for this disease and is easily mistaken for one.

Show evidence (1 reference)

PMID:34281576 SUPPORT Human Clinical

"LAMA2-CMD is one of the most common congenital muscular dystrophies (CMDs) in the world, accounting for 36.4%-48% of CMD patients"

Gives the proportion of congenital muscular dystrophy attributable to this entity.

🌍

Epidemiology

Geographic variation in reported prevalence

Published prevalence estimates for LAMA2-related dystrophy span nearly twenty-fold between countries, from 0.14 to 2.5 per 100,000. This is far more likely to reflect ascertainment and registry completeness than a real biological gradient, and it is the reason this entry records a coarse prevalence band rather than treating any point estimate as authoritative.

Show evidence (1 reference)

PMID:39213089 SUPPORT Human Clinical

"Reported prevalence varies widely between 0.14 : 100 000 (Italy) and 2.5 : 100 000 (Sweden)"

States the range of published estimates that motivates the caution recorded here.

🔀

Differential Diagnoses

Conditions with similar clinical presentations that must be differentiated from Congenital Merosin-deficient Muscular Dystrophy 1A:

Merosin-positive congenital muscular dystrophy

Overlapping Features The historical first fork: congenital muscular dystrophy with preserved merosin staining. Motor nerve conduction is normal and brain white matter is typically normal, so the two supportive tests that are abnormal in MDC1A are the ones that separate them.

Show evidence (1 reference)

PMID:8576559 SUPPORT Human Clinical

"All but two of the 10 merosin-deficient cases had reduced motor nerve conduction, whereas all the merosin-positive cases had normal results."

Shows the electrophysiological separation between the merosin-deficient and merosin-positive groups.

Dystroglycanopathies with brain malformation

Overlapping Features Fukuyama congenital muscular dystrophy, muscle-eye-brain disease and Walker-Warburg syndrome also produce congenital muscular dystrophy with cobblestone cortex, and they converge on the same pial basement membrane failure, but from the receptor side, through defective alpha-dystroglycan glycosylation, rather than from the ligand side. MDC1A was classically distinguished as the congenital muscular dystrophy without structural CNS involvement, which is now known to be only mostly true.

Show evidence (1 reference)

PMID:32827036 SUPPORT Human Clinical

"It is the most common cause of what was originally called classical, or occidental, CMD without structural involvement of the central nervous system (CNS) in distinction to CMDs with CNS involvement (Fukuyama CMD, muscle-eye-brain disease, and Walker-Warburg syndrome)"

States the classical nosological distinction and names the dystroglycanopathies it separates MDC1A from.

Limb-girdle muscular dystrophies

Overlapping Features For the partial-deficiency subtype the differential is the limb-girdle group generally. Partial merosin deficiency has been misdiagnosed as Duchenne and as unclassified limb-girdle dystrophy for years before slowed nerve conduction and white-matter change on MRI redirected the workup, which is the practical reason to check merosin in that setting.

Show evidence (2 references)

PMID:9829280 SUPPORT Human Clinical

"Partial laminin alpha 2 deficiency should be considered in the differential diagnosis of limb-girdle muscular dystrophy."

States the recommendation this differential records.

PMID:9131648 SUPPORT Human Clinical

"Merosin status should be assessed in patients with late-onset limb girdle muscular dystrophy."

Independent statement of the same recommendation from a separate late-onset family.

📊

Related Datasets

Transcriptomic analysis of fetal epaxial muscle fibers from wildtype and dyW/dyW mice at embryonic day 17.5 geo:GSE253680

Fetal muscle-fibre transcriptomes from dyW/dyW and wild-type mice at embryonic day 17.5, the point at which disease onset has been placed in this model. It is the dataset that speaks most directly to the entry's claim that the pathology begins before birth rather than accumulating after it.

house mouse BULK RNA SEQ n=7

PMID:39379105

Show evidence (1 reference)

GEO:GSE253680 SUPPORT Model Organism

"However, it is not yet known what mechanisms are faulty, right at disease onset, which in the mouse model of LAMA2-CMD dyW/dyW has been previously established to occur between embryonic days (E) 17.5 and E18.5."

The repository summary dates disease onset in this model to late gestation, which is what makes the dataset relevant to the prenatal-onset claim in the neonatal progression phase.

RNA-deep sequencing (RNA-Seq) analysis of dy2J/dy2J (Lama2-CMD mouse model), mdx (DMD mouse model) and Wild-type skeletal muscles geo:GSE126416

Whole-transcriptome profiling of dy2J/dy2J skeletal muscle at eight weeks against mdx and wild-type. The mdx comparison is what makes it useful here: it separates what is shared with a sarcolemmal dystrophy generally from what is specific to laminin-alpha2 deficiency, and the specific finding is a downregulated rather than upregulated regeneration programme.

house mouse BULK RNA SEQ n=8

PMID:31348492

Show evidence (2 references)

GEO:GSE126416 SUPPORT Model Organism

"Interestingly, significant downregulation of Pax7 was detected in dy2J/dy2J compared to upregulation of this key regeneration gene in mdx mice."

Supports the Abortive Muscle Regeneration node with a transcriptomic contrast showing the regenerative programme is suppressed in laminin-alpha2 deficiency where it is driven in a dystrophin-deficient control.

GEO:GSE126416 SUPPORT Model Organism

"Enrichment pathway analysis using Ingenuity Pathway Analysis (IPA) showed enrichment of inflammation, fibrosis, cellular movement, migration and proliferation of cells, apoptosis and necrosis in both mouse models"

Independently recovers the inflammation, fibrosis and apoptosis arms of the curated pathophysiology chain from an unbiased transcriptomic analysis.

Loss of cell-autonomously secreted laminin-α2 drives muscle stem cell dysfunction in LAMA2-related muscular dystrophy geo:GSE307443

Human iPSC-derived myogenic precursor cells, LAMA2-deficient versus control. One of the few human-cell datasets in this disease, and directly relevant to the Abortive Muscle Regeneration node because it addresses whether laminin-alpha2 acts on the progenitor cell itself rather than only on the mature fibre.

human BULK RNA SEQ n=8

PMID:41309582

Recorded without an evidence block. The repository summary states the study's motivation rather than its result, so there is no sentence in the cached record that would substantively support a specific curated claim; quoting the motivation would be a topic snippet rather than a finding.

Laminin-deficient muscular dystrophy, dy/dy diaphragm geo:GSE3252

Microarray profiling of eight-week-old dy/dy mouse diaphragm. It samples respiratory muscle pathology in a model; prominent functional diaphragm failure is not established as the driver of human MDC1A respiratory decline, where intercostal and accessory weakness is important.

house mouse MICROARRAY n=8

PMID:16368874

The dataset-discovery tool tagged this GENE_ONLY, meaning the match ran through the gene name rather than the disease name. Triaged manually and kept: the GEO title and summary both name laminin/merosin-deficient muscular dystrophy in the dy/dy mouse, so it is a true positive that the disease-name matcher missed because the record predates the LAMA2-CMD nomenclature.

🔬

Clinical Trials

NCT01805024 PHASE_I COMPLETED

CALLISTO, an ascending multiple-dose cohort study of omigapil in children and adolescents with congenital muscular dystrophy, establishing pharmacokinetics at three dose levels with safety and tolerability assessment. Twenty patients (ten LAMA2-related, ten COL6-related) were enrolled at the NIH. The trial met its primary pharmacokinetic endpoint; disease-relevant clinical assessments showed no consistent change over the twelve-week exposure, a period and design not intended to establish efficacy.

Target Phenotypes: Axial muscle weakness HP:0003327 Restrictive ventilatory defect HP:0002091

Show evidence (2 references)

clinicaltrials:NCT01805024 SUPPORT Human Clinical

"The purpose of the study is to establish the pharmacokinetic profile of omigapil in paediatric and adolescent patients with CMD and to evaluate the safety and tolerability of omigapil."

The registry record's own statement of the trial's objective.

PMID:38915423 SUPPORT Human Clinical

"This study represents the thus far only clinical trial of a therapeutic small molecule for LAMA2-RD and COL6-RD, completed with an adaptive trial design to arrive at dose adjustments."

Establishes the trial's standing as the only interventional small-molecule study in this disease.

NCT04299321 NOT_APPLICABLE COMPLETED

A completed retrospective chart review of infants and toddlers with LAMA2-CMD (n=75). Retrospective natural-history data on the youngest patients, who are the hardest group to enrol prospectively.

Show evidence (1 reference)

clinicaltrials:NCT04299321 SUPPORT Other

"This retrospective chart review study of 75-120 LAMA2-CMD patients will expand the investigators understanding of the natural history of this disease."

The registry record establishing this study's population and objective.

NCT04478981 NOT_APPLICABLE COMPLETED

LAST STRONG, a completed natural-history study (n=38) covering LAMA2- and SELENON-related disease together, framed around distinguishing them from mitochondrial myopathies.

Show evidence (1 reference)

clinicaltrials:NCT04478981 SUPPORT Other

"SEPN1 (SELENON) is a rare congenital myopathy due to mutations in the SELENON gene."

The registry record establishing this study's population and objective.

NCT06132750 NOT_APPLICABLE UNKNOWN

The five-year extension of LAST STRONG (n=40). Registry status is UNKNOWN, meaning the record has not been updated within the registry's expected window - recorded as the registry reports it rather than assumed complete.

Show evidence (1 reference)

clinicaltrials:NCT06132750 SUPPORT Other

"SELENON-related myopathy (SELENON-RM) and LAMA2-related muscular dystrophy (LAMA2-MD) are congenital neuromuscular disorders presenting with slowly, progressive axial muscle weakness, spinal rigidity, scoliosis and respiratory insufficiency."

The registry record establishing this study's population and objective.

NCT06582537 NOT_APPLICABLE COMPLETED

An ex vivo study (n=7) applying genetic correction to myogenic stem cells taken from patients. Despite the interventional-sounding title the registry classes it as observational: the correction is performed on cells, not administered to participants.

Show evidence (1 reference)

clinicaltrials:NCT06582537 SUPPORT Other

"Merosin-deficient congenital muscle dystrophy type 1a (MDC1a), or LAMA2 muscular dystrophy (LAMA2-MD) is a severe autosomal recessive form of muscular dystrophy that is caused by homozygous or compound heterozygous mutations in the laminin alpha 2 (LAMA-2) gene."

The registry record establishing this study's population and objective.

NCT06503367 NOT_APPLICABLE RECRUITING

READY CMD LAMA2, a recruiting trial-readiness study in children aged 0-5 (n=44), building the outcome measures an interventional trial in this age group would need.

Show evidence (1 reference)

clinicaltrials:NCT06503367 SUPPORT Other

"The goal of this observational study is to understand how young children with LAMA2-related dystrophy move and change over time."

The registry record establishing this study's population and objective.

🐁

Animal Models

dy3K/dy3K laminin alpha2 null mouse

The complete-null mouse and the most severe of the family, dying by about three weeks. Its value is temporal resolution rather than fidelity of course: it is the model in which the sequence of early events has been mapped, showing apoptosis at postnatal day 1, full dystrophic architecture with inflammation and matrix deposition by day 4, peak deterioration at day 7, and severe involvement of the masticatory muscles that plausibly underlies the malnutrition and death.

Species

Mouse

Genotype

Lama2 targeted null (dy3K), homozygous

Publication

PMID:31586140

Pathograph links

Myofibre Degeneration, Necrosis and Apoptosis recapitulates fidelity: high observes: cellular Reproduces the apoptotic and necrotic myofibre death of the human disease and dates its onset to the first postnatal day.

Limitations: The murine course is compressed into three weeks against a human course of decades, so the model reports the sequence of events faithfully but not their timescale. The masticatory involvement that dominates mortality here has no clear human counterpart as a cause of death.

Readouts

Apoptotic muscle fibres at postnatal day 1

Direction: INCREASED

Interpretation: Dates the onset of the apoptotic component of fibre loss.

Show evidence (1 reference)

PMID:31586140 SUPPORT Model Organism

"We found that apoptotic muscle fibres were present as early as postnatal day 1."

Reports the measurement behind this readout.

Show evidence (1 reference)

PMID:31586140 SUPPORT Model Organism

Supports treating this model as informative for the degeneration node by showing it reproduces the full dystrophic picture.

Dysregulated Muscle Proteostasis and Autophagy recapitulates fidelity: high observes: molecular Autophagy-related gene expression is raised in dy3K/dy3K muscle, and the same upregulation was confirmed in human MDC1A muscle, so the model is not merely analogous here.

Limitations: The therapeutic inference rests on systemic 3-methyladenine, a non-selective phosphoinositide 3-kinase inhibitor, so the rescue is not a clean test of autophagy alone.

Readouts

Autophagy-related gene expression in dystrophic muscle

Direction: INCREASED

Interpretation: Molecular correlate of the enhanced autophagic flux this node asserts.

Show evidence (1 reference)

PMID:21920942 SUPPORT Other

Reports the measurement in both mouse and human muscle.

Show evidence (1 reference)

PMID:21920942 SUPPORT Model Organism

"Moreover, we found that autophagy inhibition significantly improves the dystrophic dy(3K)/dy(3K) phenotype."

The intervention result that makes this model informative for the autophagy node.

Show evidence (1 reference)

PMID:31586140 SUPPORT Model Organism

"Here, we unveil the first pathogenic events and characterise the disease development in a mouse model for LAMA2-CMD (dy3K/dy3K), by analysing muscles at perinatal, neonatal and postnatal stages."

Establishes the model and the developmental-timing question it was used to answer.

dyW/dyW laminin alpha2-deficient mouse

The workhorse preclinical model, expressing a small amount of truncated protein and surviving long enough for intervention studies. Most of the therapeutic hypotheses in this disease were tested here first: Bax deletion and Bcl-2 overexpression, omigapil, integrin alpha-7 overexpression, and the mini-agrin linker. That four mechanistically unrelated interventions each extend survival in the same animal is the strongest single argument that the downstream cascade is attackable.

Species

Mouse

Genotype

Lama2 targeted mutation (dyW), homozygous, expressing a truncated laminin alpha2

Publication

PMID:15578095

Pathograph links

Myofibre Degeneration, Necrosis and Apoptosis recapitulates fidelity: high observes: cellular Apoptotic fibre death is present and is causally load-bearing: removing Bax or overexpressing Bcl-2 each produce a severalfold lifespan increase, and Bax inactivation also improves growth, histology and contractures.

Limitations: dyW mice express a truncated laminin alpha2 fragment rather than being a complete null, so the genotype corresponds to a severe hypomorph rather than to the biallelic-null human genotype it is usually taken to model.

Readouts

Lifespan under Bax inactivation or Bcl-2 overexpression

Direction: RESTORED

Interpretation: Rescue readout establishing apoptosis as a causal contributor rather than an epiphenomenon.

Show evidence (1 reference)

PMID:15578095 SUPPORT Model Organism

"We found that both of these genetic interventions produced a several-fold increase in the lifespan of Lama2(-/-) mice."

Reports the survival measurement behind this readout.

Show evidence (1 reference)

PMID:15578095 SUPPORT Model Organism

"Bax inactivation also improved postnatal growth rate and myofiber histology and decreased fixed contractures of Lama2(-/-) mice."

Shows the rescue extends to histology and contracture, not survival alone.

Failure of Basal Lamina to Sarcolemma Receptor Coupling perturbs fidelity: moderate observes: molecular Used as the test bed for restoring the coupling directly. Transgenic mini-agrin, which binds dystroglycan but not integrin alpha-7-beta-1, and a perlecan-derived chimeric protein each ameliorate the disease, including when expression is started late. Separately, transgenic integrin alpha-7 overexpression restores sarcolemmal alpha-7-beta-1 and improves pathology and life expectancy. Together these attack the two arms of the lost linkage independently.

Limitations: Both are transgenic overexpression experiments in the mouse, not deliverable therapies, and neither restores laminin-211 itself. The mini-agrin construct rebuilds only the dystroglycan arm and the integrin transgene only the integrin arm, so neither is a complete substitution.

Readouts

Lifespan and health under mini-agrin or perlecan-chimera expression

Direction: RESTORED

Interpretation: Rescue by re-linking the basement membrane to dystroglycan, which is the specific coupling this node reports as lost.

Show evidence (1 reference)

PMID:17389231 SUPPORT Model Organism

"Now we show that late-onset expression of mini-agrin still prolongs life span and improves overall health, although not to the same extent as early expression."

Reports the survival and health measurement behind this readout, including its dependence on timing.

Show evidence (2 references)

PMID:17389231 SUPPORT Model Organism

"These experiments are conceptual proof that linking the basement membrane to dystroglycan by specifically designed molecules or by endogenous ligands, could be a means to counteract MDC1A at a progressed stage of the disease, and thus opens new possibilities for the development of treatment..."

The authors' own statement that the rescue works by restoring the matrix-to-dystroglycan link, which is what makes this model informative for the coupling node.

+ 1 more reference

Show evidence (1 reference)

PMID:15578095 SUPPORT Model Organism

"To examine the significance of apoptosis in CMD1A pathogenesis, we determined whether pathogenesis in laminin-alpha2-deficient (Lama2(-/-)) mice could be ameliorated by inhibiting apoptosis"

Establishes the model and the interventional use it is cited for here.

dy2J/dy2J splice-mutant mouse

A partial-deficiency model, carrying a splice mutation that yields a truncated but partly functional protein, with a milder and longer course. It is the natural model for the limb-girdle subtype and the one in which reversibility has been shown: CRISPR-dCas9 upregulation of the paralogous Lama1 improved and partly reversed established fibrosis and hindlimb paralysis when started in symptomatic animals, against the prior expectation that fibrotic change is irreversible.

Species

Mouse

Genotype

Lama2 dy2J splice-site mutation, homozygous

Publication

PMID:31341277

Pathograph links

Endomysial Fibrosis and Replacement of Muscle rescues fidelity: moderate observes: tissue Upregulating the paralogous laminin-alpha1 prevented fibrosis and paralysis when given pre-symptomatically, and improved and partly reversed both when given after they were established.

Limitations: The rescue is by a paralogous laminin substituting for the missing one, not by restoring laminin-alpha2, so it tests the reversibility of the downstream fibrosis rather than the correction of the primary lesion. dy2J is a partial-deficiency allele, so the result speaks most directly to the milder end of the human spectrum. A companion study in a complete-deletion model found high-dose mortality and non-sustained expression, which the dy2J experiment did not surface.

Readouts

Muscle fibrosis and hindlimb paralysis after Lama1 upregulation

Direction: RESTORED

Interpretation: Reversal of established fibrotic change, which is the claim this link records.

Show evidence (1 reference)

PMID:31341277 SUPPORT Model Organism

"However, we show that dystrophic features and disease progression were improved and reversed when the treatment was initiated in symptomatic dy2j/dy2j mice with apparent hindlimb paralysis and muscle fibrosis."

Reports the reversal measurement behind this readout.

Show evidence (2 references)

PMID:31341277 SUPPORT Model Organism

"When pre-symptomatic mice were treated, Lama1 was upregulated in skeletal muscles and peripheral nerves, which prevented muscle fibrosis and paralysis."

Establishes the preventive arm of the rescue alongside the reversal arm.

+ 1 more reference

Show evidence (1 reference)

PMID:31341277 SUPPORT Model Organism

"We modulate expression of Lama1 in the dy2j/dy2j mouse model of MDC1A using an adeno-associated virus (AAV9) carrying a catalytically inactive Cas9 (dCas9), VP64 transactivators and single-guide RNAs that target the Lama1 promoter."

Establishes the model and the intervention it was used to test.

lama2 mutant zebrafish

An optically accessible model used for live fibre tracking and mechanistic perturbation. Live tracking of individual fibres showed that detachment is not immediately lethal, since detached fibres retain sarcolemmal integrity and attempt reattachment, extension and fusion before dying, which reframed the disease as having a window in which a detached fibre can be re-functionalised.

Species

Zebrafish

Genotype

lama2 loss of function

Publication

PMID:31754462

Pathograph links

Contraction-Induced Myofibre Detachment and Mechanical Injury recapitulates fidelity: moderate observes: cellular Reproduces myofibre detachment from the basal lamina and, uniquely, allows it to be watched in a living animal fibre by fibre.

Limitations: Zebrafish larval muscle is anatomically and mechanically unlike mammalian limb muscle, and the observations are made over hours in a larva rather than over years in a child, so the delay between detachment and death cannot be assumed to have the same duration in humans. In the separate Candyfloss BTS experiment, contraction inhibition began before spontaneous movement and also impaired normal muscle development. Washout was followed by structural damage in mutants and partial force recovery in siblings; this does not establish that immobilization benefits human MDC1A.

Readouts

Sarcolemmal integrity and remodelling of detached fibres

Direction: ALTERED

Interpretation: Direct observation of the detachment event and of what the fibre does afterwards.

Show evidence (1 reference)

PMID:31754462 SUPPORT Model Organism

Reports the live-imaging measurement behind this readout.

Structural damage after contraction inhibition and washout

Direction: ALTERED

Interpretation: Early BTS exposure reduces structural damage; after one day of washout, Candyfloss mutants develop patchy birefringence defects and remain weaker than siblings. Normal-sibling force only partly recovers. This is a larval perturbation result, not evidence that immobilization restores normal muscle function in patients.

Show evidence (1 reference)

PMID:26536238 SUPPORT Model Organism

"In contrast, the Caf larvae at 5dpf were weaker than their siblings (right diagram, Panel D, Fig 5) and developed structural changes with patchy alterations in birefringence (Panel C, Fig 5). These data suggest that active movement improves the mechanical function after BTS immobilization in the..."

The washout arm supports renewed activity-associated damage in the laminin-alpha2-deficient Candyfloss strain. Sapje dystrophin mutants behaved differently after washout; strain activity and mutation-specific susceptibility may both contribute.

Show evidence (1 reference)

PMID:31754462 SUPPORT Model Organism

"a process we show can be achieved by muscle specific or systemic Laminin delivery"

States the rescue the model demonstrates, which is what establishes it as an interventional as well as an observational system.

{ }

Source YAML

click to show

name: Congenital Merosin-deficient Muscular Dystrophy 1A
creation_date: "2026-09-05T18:30:00Z"
category: Mendelian
description: 'MDC1A is the severe congenital end of LAMA2-related muscular dystrophy. Biallelic
  pathogenic LAMA2 variants impair laminin alpha-2, a component of laminin-211 in muscle, peripheral
  nerve and CNS basement membranes. Loss of basal-lamina anchorage and laminin-dependent signalling
  makes muscle fibres vulnerable to injury; degeneration, altered protein turnover, impaired
  repair and fibrosis contribute to weakness and contractures. Human infant muscle histology
  demonstrates early degeneration, while the timing and contributions of apoptosis, inflammation
  and autophagy are most directly tested in animal and cell models. Regeneration is impaired
  rather than universally absent, and some injured fibres survive or recover in models.

  Severe early hypotonia and axial/proximal weakness delay motor development and usually prevent
  independent walking. Progressive contractures, spinal deformity, respiratory muscle weakness
  and impaired feeding add substantial morbidity. Clinical cohorts distinguish the congenital
  phenotype from complete merosin deficiency: these categories overlap strongly but are not
  interchangeable. Partial deficiency can accompany an early severe phenotype, and occasional
  patients classified as completely deficient walk independently. Young children may gain skills
  before later functional decline.

  Peripheral myelin abnormalities and motor conduction slowing are variable and generally contribute
  less to human weakness than in mouse models. White-matter MRI signal changes are very frequent
  after infancy and may appear by three months. Increased white-matter water content is supported
  by human MR spectroscopy; a vascular basement-membrane mechanism remains a hypothesis, and
  diffuse human demyelination is not established by the MRI appearance. Cortical neuronal migration
  abnormalities can contribute to seizures and intellectual disability in a subset, but neither
  clinical consequence is inevitable and seizures can occur without a visible cortical malformation.

  This entry focuses on congenital MDC1A, with explicitly identified observations from the broader
  partial-deficiency and limb-girdle LAMA2 spectrum. Residual protein is associated with severity
  but does not reliably predict an individual''s trajectory. Care addresses respiratory, nutritional,
  orthopedic and cardiac complications; preclinical therapeutic effects and the phase 1 omigapil
  safety study do not establish clinical disease-modifying efficacy.'
disease_term:
  preferred_term: congenital merosin-deficient muscular dystrophy 1A
  term:
    id: MONDO:0011925
    label: congenital merosin-deficient muscular dystrophy 1A
synonyms:
- MDC1A
- merosin-deficient congenital muscular dystrophy
- merosin-deficient congenital muscular dystrophy type 1A
- congenital muscular dystrophy type 1A
- LAMA2-related congenital muscular dystrophy
- LAMA2-CMD
- muscular dystrophy, congenital, merosin deficient 1A
- laminin alpha-2 chain-deficient congenital muscular dystrophy
parents:
- LAMA2-related muscular dystrophy
- Congenital Muscular Dystrophy
categories:
- Congenital Muscular Dystrophy
- Extracellular Matrix Disorder
- Basement Membrane Disorder
classifications:
  harrisons_chapter:
  - classification_value: NEUROLOGIC
    notes: >-
      A congenital muscular dystrophy: the primary clinical home is the neuromuscular-disease
      chapters of the neurologic Part.
    evidence:
    - reference: PMID:32848593
      reference_title: "LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers, and Clinical Trial Readiness."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "Complete merosin deficiency is typically associated with a more severe congenital muscular dystrophy (CMD), clinically manifested by hypotonia and weakness at birth, the development of contractures of large joints, and progressive respiratory involvement."
      explanation: Characterises the entity as a congenital muscular dystrophy, which places it in the neuromuscular chapters.
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
    notes: >-
      A single-gene autosomal recessive disorder whose severity is graded by residual protein,
      so the Mendelian axis is a substantive second home rather than a formality.
    evidence:
    - reference: PMID:22675738
      reference_title: "LAMA2 Muscular Dystrophy."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "LAMA2-MD is inherited in an autosomal recessive manner."
      explanation: GeneReviews states the Mendelian inheritance mode that motivates this Part.
inheritance:
- name: Autosomal recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    Biallelic LAMA2 variants, homozygous or compound heterozygous. Truncating alleles
    predominate in the congenital severe form; missense alleles are over-represented in the
    milder limb-girdle form, which is the molecular basis of the complete/partial deficiency
    split.
  evidence:
  - reference: PMID:22675738
    reference_title: "LAMA2 Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The diagnosis of LAMA2 muscular dystrophy is established in a proband with suggestive findings and biallelic (homozygous or compound heterozygous) pathogenic variants in LAMA2 identified by molecular genetic testing."
    explanation: States the biallelic requirement that defines the recessive mode.
  - reference: PMID:34281576
    reference_title: "Natural history and genetic study of LAMA2-related muscular dystrophy in a large Chinese cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Nonsense variants were more frequent in LAMA2-CMD (56.9%, 66/116) than in LGMDR23 (21.4%, 3/14), while missense disease-causing variants were more frequent in LGMDR23 (71.4%, 10/14) than in LAMA2-CMD (12.9%, 15/116)."
    explanation: Quantifies the allele-class skew between the congenital and limb-girdle ends of the same recessive series.
prevalence:
- population: Worldwide, children
  measure_type: POINT_PREVALENCE
  prevalence_class: BAND_1_9_PER_1000000
  rate_per_100000: 0.8
  notes: >-
    Reported as approximately 4 in 500,000 children, which normalises to 0.8 per 100,000. This
    is a review's summary figure rather than a registry count, and published estimates for
    LAMA2-related dystrophy as a whole span roughly an order of magnitude between countries, so
    the coarse band carries more weight than the point value.
  evidence:
  - reference: PMID:31308722
    reference_title: "Current understanding and treatment of cardiac and skeletal muscle pathology in laminin-α2 chain-deficient congenital muscular dystrophy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "LAMA2 MD is the most common congenital muscular dystrophy, affecting approximately 4 in 500,000 children."
    explanation: Gives the population rate normalised into this record.
- population: Switzerland, ages 0-23 years
  measure_type: POINT_PREVALENCE
  prevalence_class: BAND_1_9_PER_1000000
  rate_per_100000: 0.8
  notes: >-
    A registry-denominator minimum rather than an ascertained rate: the numerator is patients
    enrolled in the Swiss Registry for Neuromuscular Disorders, so unenrolled cases are missed
    and the authors state the figure as a floor. It covers LAMA2-related dystrophy as a whole,
    of which the congenital severe form curated here was 14 of 18 patients.
  evidence:
  - reference: PMID:39213089
    reference_title: "A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Therefore, the prevalence of LAMA2-RD in Switzerland for the age group 0-23 years is at least 17/2 123 128 = 0.8 : 100 000."
    explanation: States the registry-based minimum prevalence recorded here.
- population: Congenital muscular dystrophy cohorts, worldwide
  measure_type: UNKNOWN
  prevalence_class: RARE
  notes: >-
    Share of the congenital muscular dystrophy population rather than a population rate. Recorded
    because it is the figure most often quoted for this disease and is easily mistaken for one.
  evidence:
  - reference: PMID:34281576
    reference_title: "Natural history and genetic study of LAMA2-related muscular dystrophy in a large Chinese cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "LAMA2-CMD is one of the most common congenital muscular dystrophies (CMDs) in the world, accounting for 36.4%-48% of CMD patients"
    explanation: Gives the proportion of congenital muscular dystrophy attributable to this entity.
mappings:
  mondo_mappings:
  - term:
      id: MONDO:0100228
      label: LAMA2-related muscular dystrophy
    mapping_predicate: skos:broadMatch
    mapping_source: MONDO
    mapping_justification: MONDO:0011925 identifies the congenital disease emphasized here.
      MONDO:0100228 denotes the broader LAMA2-related muscular dystrophy spectrum, from which
      explicitly scoped comparative observations are included; it is a broad match rather than
      an equivalent label for MDC1A.
has_subtypes:
- name: Complete deficiency
  display_name: Complete deficiency of merosin
  description: Absent laminin alpha-2 on muscle immunostaining, usually associated with a severe
    congenital phenotype and failure to achieve independent walking. Some cohorts classify deficiency
    using genotype or clinical information when biopsy is unavailable. Complete deficiency and
    congenital clinical onset are correlated but not identical categories; rare ambulant exceptions
    occur.
  evidence:
  - reference: PMID:32848593
    reference_title: "LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers, and Clinical Trial Readiness."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Muscle atrophy and severe weakness typically prevent independent ambulation."
    explanation: States the defining functional consequence of the complete-deficiency phenotype.
- name: Partial deficiency
  display_name: Partial deficiency of merosin
  description: 'Reduced but detectable laminin alpha-2 is often associated with a milder limb-girdle
    presentation and retained ambulation. Partial deficiency is not synonymous with late onset:
    congenital, severe presentations also occur. Cohorts classified by clinical onset or walking
    ability cannot be read as immunostaining-defined subgroups.'
  evidence:
  - reference: PMID:32848593
    reference_title: "LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers, and Clinical Trial Readiness."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Partial merosin deficiency is mostly manifested by later onset limb-girdle weakness and joint contractures so that independent ambulation is typically achieved."
    explanation: Defines the partial-deficiency phenotype and its ambulatory outcome.
  - reference: PMID:9829280
    reference_title: "Laminin alpha 2-chain gene mutations in two siblings presenting with limb-girdle muscular dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These data confirm that mutations of the LAMA2 gene that do not completely disrupt the production of the protein can give rise to phenotypes considerably milder than classical merosin-deficient congenital muscular dystrophy."
    explanation: Establishes the residual-protein rule that makes this a graded subtype of the same disease rather than a distinct entity.
  - reference: PMID:34281576
    reference_title: "Natural history and genetic study of LAMA2-related muscular dystrophy in a large Chinese cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All LGMDR23 patients achieved independent ambulation at median age of 18.0 months (range 13.0-20.0 months)."
    explanation: All clinically classified LGMDR23 patients in this cohort walked independently;
      this is not a direct estimate for every patient with partial merosin staining.
pathophysiology:
- name: Biallelic LAMA2 Loss of Function
  biological_scale: MOLECULAR
  description: >-
    Two damaged copies of LAMA2, at 6q22-q23, remove or truncate the laminin alpha-2 chain.
    Most congenital-severe alleles are premature termination codons or exon deletions; missense
    alleles that leave residual protein are enriched at the milder end of the spectrum. Because
    laminin-211 is an obligate alpha2-beta1-gamma1 heterotrimer, loss of the single alpha-2
    chain removes the assembled trimer rather than merely weakening it.
  genes:
  - preferred_term: LAMA2
    term:
      id: hgnc:6482
      label: LAMA2
  downstream:
  - target: Loss of Laminin-211 from the Muscle Basal Lamina
    causal_link_type: DIRECT
    description: >-
      The alpha-2 chain is the isoform-defining subunit of laminin-211, so a null allele pair
      removes the trimer from every basement membrane that depends on it.
    evidence:
    - reference: PMID:31341277
      reference_title: "A mutation-independent approach for muscular dystrophy via upregulation of a modifier gene."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "MDC1A is caused by mutations in LAMA2 that lead to nonfunctional laminin-α2, which compromises the stability of muscle fibres and the myelination of peripheral nerves."
      explanation: States the step from LAMA2 mutation to nonfunctional laminin-alpha-2 and thence to loss of fibre stability, which is this edge.
  - target: Loss of Laminin-211 from the Schwann Cell Basal Lamina
    causal_link_type: DIRECT
    description: >-
      The same null genotype removes laminin-211 from Schwann cell basal laminae, where the
      alpha-2 chain is likewise the predominant laminin alpha subunit.
  - target: Loss of Laminin-211 at the Glia Limitans and CNS Vascular Basement Membranes
    causal_link_type: DIRECT
    description: >-
      Laminin alpha-2 is deposited by astrocyte endfeet, so a systemic null genotype withdraws
      it from the pial and perivascular basement membranes of the brain as well.
  - target: Dysregulated Muscle Proteostasis and Autophagy
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Laminin-alpha2 deficiency alters muscle proteostasis in experimental models;
      the intervening signalling and human causal contribution remain incompletely established.
    evidence:
    - reference: PMID:21920942
      reference_title: Autophagy is increased in laminin α2 chain-deficient muscle and its inhibition
        improves muscle morphology in a mouse model of MDC1A.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Using the dy(3K)/dy(3K) mouse model of laminin α2 chain deficiency and MDC1A
        patient muscle, we show here that expression of autophagy-related genes is upregulated
        in laminin α2 chain-deficient muscle.
      explanation: The quoted claim combines human tissue and mouse expression data; the interventional
        causal evidence is separately assigned to the mouse model.
  - target: Impaired Muscle Regeneration
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Loss of cell-autonomously secreted laminin-alpha2 slows myogenic precursor
      proliferation in engineered human cells and delays regeneration in muscle stem-cell-specific
      mouse knockouts.
    evidence:
    - reference: PMID:41309582
      reference_title: Loss of cell-autonomously secreted laminin-α2 drives muscle stem cell
        dysfunction in LAMA2-related muscular dystrophy.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: This indicated that deletion of LAMA2 in human myogenic precursor cells is sufficient
        to slow cell-cycle progression.
      explanation: Engineered LAMA2 knockout in healthy-donor iPSC-derived myogenic precursors,
        not patient cells, establishes a culture-level proliferative defect.
  - target: Loss of Myocardial Laminin-211 Support
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Systemic LAMA2 deficiency affects laminin-alpha2-dependent myocardial matrix;
      the cardiac physiological consequence is provisional.
    evidence:
    - reference: PMID:31308722
      reference_title: Current understanding and treatment of cardiac and skeletal muscle pathology
        in laminin-α2 chain-deficient congenital muscular dystrophy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: As laminin-211 is a major component of the myocardial ECM, it is likely that
        its loss will have important implications for cardiac physiology.
      explanation: The review proposes a myocardial ECM mechanism; the intermediate cause of
        human ventricular dysfunction remains uncertain.
  evidence:
  - reference: PMID:7550355
    reference_title: "Mutations in the laminin alpha 2-chain gene (LAMA2) cause merosin-deficient congenital muscular dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We therefore investigated LAMA2 for the presence of disease-causing mutations in laminin alpha 2 chain-deficient CMD families and now report splice site and nonsense mutations in two families leading presumably to a truncated laminin alpha 2 protein."
    explanation: The original report establishing LAMA2 as the mutated gene and truncation as the allele class.
  - reference: PMID:34281576
    reference_title: "Natural history and genetic study of LAMA2-related muscular dystrophy in a large Chinese cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The top three high-frequency disease-causing variants in Han Chinese patients were c.7147C > T (p.R2383*), exon 4 deletion, and c.5156_5159del (p.K1719Rfs*5)."
    explanation: Shows that the recurrent alleles in a large cohort are nonsense, whole-exon deletion and frameshift, that is, loss-of-function classes.
- name: Loss of Laminin-211 from the Muscle Basal Lamina
  biological_scale: MOLECULAR
  description: >-
    Laminin-211 is the predominant laminin of the skeletal-muscle basement membrane. Without the
    alpha-2 chain the basal lamina loses both its principal polymerising alpha subunit and the
    long-arm LG module that tethers the lattice to the fibre surface, so the sheet is destabilised
    and its cell-facing end is unanchored.
  cellular_components:
  - preferred_term: muscle fibre basal lamina
    term:
      id: GO:0005604
      label: basement membrane
  molecular_functions:
  - preferred_term: laminin-211 as a basement-membrane structural constituent
    term:
      id: GO:0005201
      label: extracellular matrix structural constituent
    modifier: DECREASED
  downstream:
  - target: Failure of Basal Lamina to Sarcolemma Receptor Coupling
    causal_link_type: DIRECT
    description: >-
      The receptors remain in the membrane but their ligand is gone, so the linkage fails from
      the matrix side.
  evidence:
  - reference: PMID:31308722
    reference_title: "Current understanding and treatment of cardiac and skeletal muscle pathology in laminin-α2 chain-deficient congenital muscular dystrophy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Laminin-211 is an extracellular matrix protein that functions to stabilize the basement membrane and muscle fibers during contraction."
    explanation: States the structural role of laminin-211 in the muscle basement membrane that this node reports as lost.
- name: Failure of Basal Lamina to Sarcolemma Receptor Coupling
  biological_scale: MOLECULAR
  description: Laminin-211 connects basal lamina with sarcolemmal dystroglycan and integrin
    alpha-7-beta-1 receptor systems. Its loss weakens matrix-to-cytoskeletal anchorage and adhesion-dependent
    signalling; receptor abundance and compensating laminin expression can also change. Loss
    of laminin-211 does not mean that every extracellular-matrix attachment is absent.
  molecular_functions:
  - preferred_term: laminin-211 binding by alpha-dystroglycan and integrin alpha-7-beta-1
    term:
      id: GO:0043236
      label: laminin binding
    modifier: DECREASED
  biological_processes:
  - preferred_term: myofibre adhesion to the basal lamina
    term:
      id: GO:0031589
      label: cell-substrate adhesion
    modifier: DECREASED
  downstream:
  - target: Contraction-Induced Myofibre Detachment and Mechanical Injury
    causal_link_type: DIRECT
    description: >-
      With the mechanical arm of the bridge gone, contractile force is no longer transmitted
      across an intact linkage and the fibre pulls away from its matrix.
  - target: Loss of Laminin-Dependent Survival Signalling
    causal_link_type: DIRECT
    description: >-
      The same receptors carry adhesion-dependent survival signalling, so the signalling arm
      fails at the same moment as the mechanical one.
  evidence:
  - reference: PMID:21798088
    reference_title: "Skeletal muscle laminin and MDC1A: pathogenesis and treatment strategies."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "By binding to the cell surface receptors dystroglycan and integrin α7β1, laminin-211 is believed to protect the muscle fiber from damage under the constant stress of contractions, and to influence signal transmission events."
    explanation: States both arms of the linkage, mechanical protection and signal transmission, that this node reports as jointly lost.
  - reference: PMID:37182895
    reference_title: "Brain MRI Abnormalities, Epilepsy and Intellectual Disability in LAMA2 Related Dystrophy - a Genotype/Phenotype Correlation."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "the LG domain (LG), which binds to the glycosylated residues of α-dystroglycan and to the integrins"
    explanation: Identifies the LG module as the receptor-binding domain, which is the structural basis for the coupling described here.
  - reference: PMID:32827036
    reference_title: "Cobblestone Malformation in LAMA2 Congenital Muscular Dystrophy (MDC1A)."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "This results in a loss of the stabilizing connection to the DGC, leading to a loss of structural integrity and function of various cells, including myocytes and Schwann cells"
    explanation: States the loss of the dystroglycan-complex connection following failure of merosin to serve as a matriglycan acceptor, which is the dystroglycan arm of this node.
  - reference: PMID:21652631
    reference_title: "Transgenic overexpression of the α7 integrin reduces muscle pathology and improves viability in the dy(W) mouse model of merosin-deficient congenital muscular dystrophy type 1A."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "MDC1A patients exhibit reduced α7β1 integrin; however, it is unclear how the secondary loss of α7β1 integrin contributes to MDC1A disease progression."
    explanation: This abstract background statement summarizes secondary integrin reduction
      in patients; the experiment itself tested integrin overexpression in mice.
- name: Contraction-Induced Myofibre Detachment and Mechanical Injury
  biological_scale: CELLULAR
  description: Loss of laminin-dependent anchorage permits contraction-associated fibre detachment
    and injury. In lama2-deficient zebrafish, detached fibres retain membrane integrity and
    many survive or reattach; detachment is not synonymous with immediate cell death. Early
    pharmacological inhibition of contraction reduces larval structural damage but also impairs
    force development in mutants and controls. Damage reappears after washout in Candyfloss
    mutants, supporting activity-dependent injury without demonstrating human therapeutic benefit.
  cell_types:
  - preferred_term: skeletal muscle fibre
    term:
      id: CL:0008002
      label: skeletal muscle fiber
  locations:
  - preferred_term: skeletal muscle tissue
    term:
      id: UBERON:0001134
      label: skeletal muscle tissue
  downstream:
  - target: Myofibre Degeneration, Necrosis and Apoptosis
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Loss of anchorage increases vulnerability to degeneration, but not every detached
      fibre dies. The timing and route differ between experimental models and are not directly
      tracked in human muscle.
    evidence:
    - reference: PMID:31308722
      reference_title: Current understanding and treatment of cardiac and skeletal muscle pathology
        in laminin-α2 chain-deficient congenital muscular dystrophy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: When the laminin-α2 chain is defective or absent, muscle fibers experience mechanical
        stress and become susceptible to tearing and fragmentation, resulting in tissue injury
        and degeneration.
      explanation: The review supports mechanical vulnerability leading to degeneration; zebrafish
        survival data limit any deterministic reading.
  evidence:
  - reference: PMID:31754462
    reference_title: "Cellular rescue in a zebrafish model of congenital muscular dystrophy type 1A."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Here we show, via live tracking of individual muscle fibres, that dystrophic myofibres in the zebrafish model of MDC1A maintain sarcolemmal integrity and undergo dynamic remodelling behaviours post detachment, including focal sarcolemmal reattachment, cell extension and hyper-fusion with surrounding myoblasts."
    explanation: Directly observes myofibre detachment in a laminin-deficient animal and characterises what the fibre does next.
  - reference: PMID:26536238
    reference_title: Immobilization of Dystrophin and Laminin α2-Chain Deficient Zebrafish Larvae
      In Vivo Prevents the Development of Muscular Dystrophy.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: A key finding of this study is that the BTS immobilization reduced the muscle damage
      occurring in freely moving Sap and Caf larvae. Although BTS treatment generally weakened muscle
      function, as discussed above, it also abolished the difference in force between the mutated
      larvae and their normal siblings.
    explanation: BTS exposure from 18 hours to 4 days post-fertilization reduced structural damage
      in Candyfloss lama2 mutants and Sapje dystrophin mutants. Force was also reduced in both mutants
      and normal siblings, so structural protection is not restoration of normal contractile function.
  - reference: PMID:26536238
    reference_title: Immobilization of Dystrophin and Laminin α2-Chain Deficient Zebrafish Larvae
      In Vivo Prevents the Development of Muscular Dystrophy.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: We thus consider BTS to abolish contraction in the larvae via direct effects on the contractile
      system, without interfering with motor nerves, muscle activation or imposing external constraints.
    explanation: The authors interpret this actin-myosin inhibitor as mechanical silencing through
      the contractile apparatus, not motor-nerve paralysis or external restraint. The experiment supports
      activity-dependent injury in larvae without establishing membrane rupture, a specific human
      effect size, or clinical benefit from immobilization.
- name: Loss of Laminin-Dependent Survival Signalling
  biological_scale: CELLULAR
  description: Merosin promoted stability and prevented apoptosis in cultured human rhabdomyosarcoma
    and mouse C2C12 myogenic cell lines. These were not patient-derived myoblasts. The assay
    supports a survival-signalling function but does not establish that other laminins can never
    compensate in vivo.
  biological_processes:
  - preferred_term: myofibre apoptosis
    term:
      id: GO:0010657
      label: muscle cell apoptotic process
    modifier: INCREASED
  downstream:
  - target: Myofibre Degeneration, Necrosis and Apoptosis
    causal_link_type: DIRECT
    description: Loss of laminin-dependent survival signalling can promote myotube apoptosis
      in culture; translation to its quantitative contribution to human fibre loss remains uncertain.
  evidence:
  - reference: PMID:8830776
    reference_title: "Merosin and laminin in myogenesis; specific requirement for merosin in myotube stability and survival."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Finally, merosin appears to promote myotube stability by preventing apoptosis."
    explanation: States the anti-apoptotic function of merosin whose loss this node describes.
  - reference: PMID:8830776
    reference_title: "Merosin and laminin in myogenesis; specific requirement for merosin in myotube stability and survival."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Exogenous merosin converted these myotubes to a stable phenotype, while laminin had no effect."
    explanation: Merosin rescued myotube stability in the tested cell lines; the negative laminin
      comparison is assay-specific, not a universal prohibition on paralog compensation.
- name: Myofibre Degeneration, Necrosis and Apoptosis
  biological_scale: CELLULAR
  description: >-
    Fibres die by both necrosis and apoptosis, and the apoptotic component is unusually
    prominent for a muscular dystrophy, prominent enough to be a therapeutic target in its own
    right. In the dy3K/dy3K null mouse, apoptotic fibres are already present at postnatal day 1,
    before any other dystrophic hallmark. That two Bcl-2-family manipulations, and separately a
    GAPDH-Siah1 pathway inhibitor, each extend survival severalfold makes apoptosis causal here
    rather than incidental.
  cell_types:
  - preferred_term: skeletal muscle fibre
    term:
      id: CL:0008002
      label: skeletal muscle fiber
  biological_processes:
  - preferred_term: muscle cell apoptotic process
    term:
      id: GO:0010657
      label: muscle cell apoptotic process
    modifier: INCREASED
  downstream:
  - target: Inflammatory Cell Recruitment
    causal_link_type: DIRECT
    description: Degenerating and necrotic fibres recruit macrophages, and the infiltrate appears
      within days of birth in the null mouse.
  - target: Impaired mastication
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Dystrophic injury of masticatory muscles is a plausible contributor to impaired
      chewing. The tissue distribution and nutritional effect are supported in dy3K mice, while
      the quantitative contribution to human feeding difficulty remains uncertain.
    evidence:
    - reference: PMID:31586140
      reference_title: Early skeletal muscle pathology and disease progress in the dy(3K)/dy(3K)
        mouse model of congenital muscular dystrophy with laminin α2 chain-deficiency.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: We found that masticatory muscles were severely affected in dy3K/dy3K mice and
        this may be an underlying cause of their malnutrition, which contributes to death around
        day 21.
      explanation: Severe masticatory muscle injury is directly observed in dy3K mice; the authors
        propose a nutritional consequence. Translation to human chewing impairment is provisional,
        with clinical mastication difficulty documented separately.
  evidence:
  - reference: PMID:31586140
    reference_title: "Early skeletal muscle pathology and disease progress in the dy(3K)/dy(3K) mouse model of congenital muscular dystrophy with laminin α2 chain-deficiency."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We found that apoptotic muscle fibres were present as early as postnatal day 1."
    explanation: Places myofibre apoptosis at the earliest detectable point of the disease in the complete-null model.
  - reference: PMID:15578095
    reference_title: "Inhibition of apoptosis improves outcome in a model of congenital muscular dystrophy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Laminin-alpha2-deficient skeletal muscles in both humans and mice show signs of muscle cell death by apoptosis."
    explanation: This is a background synthesis of prior human and mouse observations, distinct
      from the paper’s mouse Bax/Bcl-2 intervention results.
  - reference: PMID:31586140
    reference_title: "Early skeletal muscle pathology and disease progress in the dy(3K)/dy(3K) mouse model of congenital muscular dystrophy with laminin α2 chain-deficiency."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Typical hallmarks of LAMA2-CMD dystrophic muscle biopsy include: degenerating/regenerating muscle fibres, muscle fibre atrophy, necrosis and apoptosis of muscle cells, early inflammation and extensive connective tissue infiltration"
    explanation: This introductory summary describes known biopsy hallmarks; the primary time-course
      experiment was in dy3K mice.
  - reference: PMID:11369186
    reference_title: Massive muscle cell degeneration in the early stage of merosin-deficient
      congenital muscular dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: These findings imply that massive muscle fiber degeneration occurs in the very
      early stage of merosin-deficient CMD and may contribute to the severe dystrophic changes
      in muscle from early infancy.
    explanation: The primary study examined ten patients and supports early human muscle degeneration;
      the very early massive injury was age-dependent.
- name: Dysregulated Muscle Proteostasis and Autophagy
  biological_scale: CELLULAR
  description: Autophagy-related transcripts are increased in sampled human and dy3K mouse muscle.
    The nonspecific inhibitor 3-methyladenine improved several mouse outcomes, supporting a
    contribution of altered protein turnover. Transcript abundance and this intervention do
    not establish uniformly excessive autophagic flux or an exclusively harmful role in patients.
  biological_processes:
  - preferred_term: macroautophagy
    term:
      id: GO:0016236
      label: macroautophagy
    modifier: INCREASED
  downstream:
  - target: Muscle Atrophy and Loss of Muscle Mass
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Mouse 3-methyladenine treatment supports a contribution of altered degradation
      to atrophy, with uncertain pathway specificity and human effect size.
    evidence:
    - reference: PMID:21920942
      reference_title: "Autophagy is increased in laminin α2 chain-deficient muscle and its inhibition improves muscle morphology in a mouse model of MDC1A."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "In particular, we show that systemic injection of 3-methyladenine (3-MA) reduces muscle fibrosis, atrophy, apoptosis and increases muscle regeneration and muscle mass."
      explanation: Blocking autophagy reverses the atrophy, which is the intervention evidence for this edge.
  evidence:
  - reference: PMID:21920942
    reference_title: "Autophagy is increased in laminin α2 chain-deficient muscle and its inhibition improves muscle morphology in a mouse model of MDC1A."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Using the dy(3K)/dy(3K) mouse model of laminin α2 chain deficiency and MDC1A patient muscle, we show here that expression of autophagy-related genes is upregulated in laminin α2 chain-deficient muscle."
    explanation: The quoted claim combines human tissue and mouse expression data; the interventional
      causal evidence is separately assigned to the mouse model.
  mechanism_confidence: PROVISIONAL
- name: Impaired Muscle Regeneration
  biological_scale: CELLULAR
  description: 'Laminin-alpha2 deficiency can impair muscle stem-cell proliferation and delay
    repair. Regeneration remains possible: mouse and zebrafish studies show repair and fibre
    recovery. LAMA2 knockout in healthy-donor isogenic human iPSC-derived myogenic precursors
    slowed cell-cycle progression, while differentiation remained possible; this is cell-model
    evidence rather than a measured patient stem-cell defect.'
  cell_types:
  - preferred_term: skeletal muscle satellite cell
    term:
      id: CL:0000594
      label: skeletal muscle satellite cell
  biological_processes:
  - preferred_term: skeletal muscle tissue regeneration
    term:
      id: GO:0043403
      label: skeletal muscle tissue regeneration
    modifier: DECREASED
  downstream:
  - target: Endomysial Fibrosis and Replacement of Muscle
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      What regeneration fails to replace is replaced by connective tissue instead.
  - target: Muscle Atrophy and Loss of Muscle Mass
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Repair that cannot keep pace with degeneration contributes to loss of muscle
      mass; impaired fibre growth and increased protein degradation also contribute.
  evidence:
  - reference: PMID:31754462
    reference_title: "Cellular rescue in a zebrafish model of congenital muscular dystrophy type 1A."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We further reveal that Laminin also acts as a pro-regenerative factor that stimulates muscle stem cell-mediated repair in lama2-deficient animals in vivo."
    explanation: Shows the regenerative deficit is itself laminin-dependent, which is the specific claim this node makes.
  - reference: PMID:35203715
    reference_title: "Oxidative Stress, Inflammation and Connexin Hemichannels in Muscular Dystrophies."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Consequently, MDC1A-causing mutations in the LAMA2 gene lead to a defective muscle repair associated with chronic inflammation, fibrosis, and muscle atrophy"
    explanation: States the defective-repair-to-fibrosis-and-atrophy sequence that this node and its downstream targets describe.
  - reference: PMID:41309582
    reference_title: Loss of cell-autonomously secreted laminin-α2 drives muscle stem cell dysfunction
      in LAMA2-related muscular dystrophy.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: This indicated that deletion of LAMA2 in human myogenic precursor cells is sufficient
      to slow cell-cycle progression.
    explanation: Engineered LAMA2 knockout in healthy-donor iPSC-derived myogenic precursors,
      not patient cells, establishes a culture-level proliferative defect.
- name: Inflammatory Cell Recruitment
  biological_scale: TISSUE
  description: Inflammatory infiltration accompanies early fibre injury and persists in dystrophic
    mouse muscle. Chronic inflammatory signalling can impair myogenesis and sustain fibroblast
    activation, but early inflammatory and matrix responses can also support repair; their effect
    depends on timing and context.
  cell_types:
  - preferred_term: macrophage
    term:
      id: CL:0000235
      label: macrophage
  biological_processes:
  - preferred_term: inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
    modifier: INCREASED
  downstream:
  - target: Endomysial Fibrosis and Replacement of Muscle
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Chronic infiltrate is the standard driver of mesenchymal activation and matrix deposition
      in injured muscle.
    evidence:
    - reference: PMID:31308722
      reference_title: Current understanding and treatment of cardiac and skeletal muscle pathology
        in laminin-α2 chain-deficient congenital muscular dystrophy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: However, in situations with chronic tissue damage such as in LAMA2 MD, inflammatory
        cell infiltration and fibroblast activation persist while satellite cells are being
        constantly depleted due to the muscle experiencing continuous cycles of degeneration
        and regeneration.
      explanation: The mechanistic review links chronic injury, persistent inflammation and
        fibroblast activation.
  - target: Increased endomysial connective tissue
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Persistent inflammation and fibroblast activation promote matrix deposition
      in chronically injured muscle; this upstream relation is distinct from equating biopsy
      collagen with a fibrosis node.
    evidence:
    - reference: PMID:31308722
      reference_title: Current understanding and treatment of cardiac and skeletal muscle pathology
        in laminin-α2 chain-deficient congenital muscular dystrophy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: However, in situations with chronic tissue damage such as in LAMA2 MD, inflammatory
        cell infiltration and fibroblast activation persist while satellite cells are being
        constantly depleted due to the muscle experiencing continuous cycles of degeneration
        and regeneration.
      explanation: The mechanistic review links chronic injury, persistent inflammation and
        fibroblast activation.
  evidence:
  - reference: PMID:35203715
    reference_title: "Oxidative Stress, Inflammation and Connexin Hemichannels in Muscular Dystrophies."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "In DyW mice, a murine model of laminin-deficient muscular dystrophy, merosin-deficient skeletal muscles exhibit high macrophage infiltration from early ages to adulthood."
    explanation: Documents the early and sustained macrophage infiltration this node reports.
  - reference: PMID:31586140
    reference_title: "Early skeletal muscle pathology and disease progress in the dy(3K)/dy(3K) mouse model of congenital muscular dystrophy with laminin α2 chain-deficiency."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Other typical dystrophic hallmarks (muscle degeneration, inflammation, and extensive production of the extracellular matrix proteins) were clearly evident already at postnatal day 4, and the highest degree of muscle deterioration was reached by day 7."
    explanation: Times the inflammatory infiltrate and matrix production to the first postnatal week in the complete-null model.
- name: Endomysial Fibrosis and Replacement of Muscle
  biological_scale: TISSUE
  conforms_to: "fibrotic_response#Excessive ECM Deposition"
  description: Persistent fibroblast activation and matrix deposition accompany muscle degeneration
    and impaired repair. Fibrogenesis can contribute to early contractures; the timing and cellular
    contributions in individual human muscles are less directly resolved than in experimental
    models.
  cell_types:
  - preferred_term: myofibroblast
    term:
      id: CL:0000186
      label: myofibroblast cell
  biological_processes:
  - preferred_term: extracellular matrix organization
    term:
      id: GO:0030198
      label: extracellular matrix organization
    modifier: INCREASED
  downstream:
  - target: Joint contracture
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Fibrogenesis shortens and stiffens muscle and periarticular tissues, contributing
      to early and progressive flexion contractures.
    evidence:
    - reference: PMID:39213089
      reference_title: A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related
        Muscular Dystrophy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Pathophysiologically, early fibrogenesis results in severe and early contractures
        of joints and loss of muscle tissue by myofibroblast transdifferentiation
      explanation: The cohort introduction summarizes a fibrogenic mechanism from prior work
        rather than directly testing it in these patients.
  - target: Elbow flexion contracture
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: The documented joint-specific contracture is a clinical consequence of the
      general fibrogenic shortening process; the cited mechanism is not a joint-specific intervention
      experiment.
    evidence:
    - reference: PMID:39213089
      reference_title: A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related
        Muscular Dystrophy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Pathophysiologically, early fibrogenesis results in severe and early contractures
        of joints and loss of muscle tissue by myofibroblast transdifferentiation
      explanation: The cohort introduction summarizes a fibrogenic mechanism from prior work
        rather than directly testing it in these patients.
  - target: Knee flexion contracture
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: The documented joint-specific contracture is a clinical consequence of the
      general fibrogenic shortening process; the cited mechanism is not a joint-specific intervention
      experiment.
    evidence:
    - reference: PMID:39213089
      reference_title: A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related
        Muscular Dystrophy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Pathophysiologically, early fibrogenesis results in severe and early contractures
        of joints and loss of muscle tissue by myofibroblast transdifferentiation
      explanation: The cohort introduction summarizes a fibrogenic mechanism from prior work
        rather than directly testing it in these patients.
  - target: Hip flexion contracture
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: The documented joint-specific contracture is a clinical consequence of the
      general fibrogenic shortening process; the cited mechanism is not a joint-specific intervention
      experiment.
    evidence:
    - reference: PMID:39213089
      reference_title: A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related
        Muscular Dystrophy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Pathophysiologically, early fibrogenesis results in severe and early contractures
        of joints and loss of muscle tissue by myofibroblast transdifferentiation
      explanation: The cohort introduction summarizes a fibrogenic mechanism from prior work
        rather than directly testing it in these patients.
  - target: Ankle contracture
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: The documented joint-specific contracture is a clinical consequence of the
      general fibrogenic shortening process; the cited mechanism is not a joint-specific intervention
      experiment.
    evidence:
    - reference: PMID:39213089
      reference_title: A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related
        Muscular Dystrophy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Pathophysiologically, early fibrogenesis results in severe and early contractures
        of joints and loss of muscle tissue by myofibroblast transdifferentiation
      explanation: The cohort introduction summarizes a fibrogenic mechanism from prior work
        rather than directly testing it in these patients.
  - target: Finger flexion contracture
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: The documented joint-specific contracture is a clinical consequence of the
      general fibrogenic shortening process; the cited mechanism is not a joint-specific intervention
      experiment.
    evidence:
    - reference: PMID:39213089
      reference_title: A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related
        Muscular Dystrophy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Pathophysiologically, early fibrogenesis results in severe and early contractures
        of joints and loss of muscle tissue by myofibroblast transdifferentiation
      explanation: The cohort introduction summarizes a fibrogenic mechanism from prior work
        rather than directly testing it in these patients.
  evidence:
  - reference: PMID:39213089
    reference_title: "A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Pathophysiologically, early fibrogenesis results in severe and early contractures of joints and loss of muscle tissue by myofibroblast transdifferentiation"
    explanation: The cohort introduction summarizes a fibrogenic mechanism from prior work rather
      than directly testing it in these patients.
  - reference: PMID:7550355
    reference_title: "Mutations in the laminin alpha 2-chain gene (LAMA2) cause merosin-deficient congenital muscular dystrophy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Histological changes seen in muscle biopsies consist of large variations in muscle fibre size, a few necrotic and regenerating fibres and a marked increase in endomysial collagen tissue."
    explanation: Records the endomysial collagen increase as a defining biopsy feature of this disease group.
- name: Muscle Atrophy and Loss of Muscle Mass
  biological_scale: TISSUE
  description: 'Muscle mass is reduced by fibre injury, inadequate repair and altered protein
    turnover. Atrophy is not solely a count of lost fibres: dy3K muscle can regain fibre number
    while retaining small fibres. Axial and proximal clinical weakness cannot itself quantify
    the amount of atrophy.'
  locations:
  - preferred_term: skeletal muscle tissue
    term:
      id: UBERON:0001134
      label: skeletal muscle tissue
  downstream:
  - target: Axial muscle weakness
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Loss and dysfunction of contractile tissue contribute to axial force loss;
      tissue amount is not the sole determinant of strength.
  - target: Proximal muscle weakness
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: The same muscle degeneration and atrophy contribute to proximal limb weakness;
      the distribution is supported independently by clinical examination.
  - target: Facial muscle weakness
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Facial muscle involvement is part of the myopathic process; the precise contribution
      of fibre loss versus dysfunction is not quantified.
  - target: Neonatal hypotonia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Early dystrophic muscle injury and loss of effective contractile tissue contribute
      to low tone in congenital disease; tone and strength remain distinct clinical findings.
    evidence:
    - reference: PMID:11369186
      reference_title: Massive muscle cell degeneration in the early stage of merosin-deficient
        congenital muscular dystrophy.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: These findings imply that massive muscle fiber degeneration occurs in the very
        early stage of merosin-deficient CMD and may contribute to the severe dystrophic changes
        in muscle from early infancy.
      explanation: The primary study examined ten patients and supports early human muscle degeneration;
        the very early massive injury was age-dependent.
  - target: Respiratory Muscle Weakness and Reduced Chest Wall Compliance
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: The muscle disease affects intercostal and accessory muscles, reducing effective
      respiratory force and chest-wall expansion.
    evidence:
    - reference: PMID:31308722
      reference_title: Current understanding and treatment of cardiac and skeletal muscle pathology
        in laminin-α2 chain-deficient congenital muscular dystrophy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Weakness of intercostal and accessory muscles results in progressive restriction
        of the chest wall, decreased lung volume, reduced alveolar gas exchange, and eventually
        restrictive respiratory insufficiency.
      explanation: The clinical mechanistic review explicitly states the respiratory causal
        sequence.
  evidence:
  - reference: PMID:31308722
    reference_title: Current understanding and treatment of cardiac and skeletal muscle pathology
      in laminin-α2 chain-deficient congenital muscular dystrophy.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Besides impaired regeneration, the imbalance between protein synthesis and protein
      breakdown is another factor leading to loss of muscle mass and muscle atrophy in LAMA2
      MD.
    explanation: Review synthesis of impaired repair and protein turnover, rather than inference
      of atrophy from motor-function scores.
- name: Respiratory Muscle Weakness and Reduced Chest Wall Compliance
  biological_scale: ORGANISM
  description: Weak intercostal and accessory muscles reduce chest-wall expansion, lung volume
    and gas exchange. Spinal deformity can add thoracic restriction or airway compression. This
    mechanism explains restrictive physiology and respiratory insufficiency; human studies show
    relative functional diaphragm preservation despite severe overall disease.
  downstream:
  - target: Restrictive ventilatory defect
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Reduced chest-wall expansion and lung volumes produce restrictive ventilatory
      physiology.
    evidence:
    - reference: PMID:31308722
      reference_title: Current understanding and treatment of cardiac and skeletal muscle pathology
        in laminin-α2 chain-deficient congenital muscular dystrophy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Weakness of intercostal and accessory muscles results in progressive restriction
        of the chest wall, decreased lung volume, reduced alveolar gas exchange, and eventually
        restrictive respiratory insufficiency.
      explanation: The clinical mechanistic review explicitly states the respiratory causal
        sequence.
  - target: Respiratory insufficiency due to muscle weakness
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Impaired ventilation and gas exchange can progress to clinically significant
      respiratory insufficiency.
    evidence:
    - reference: PMID:31308722
      reference_title: Current understanding and treatment of cardiac and skeletal muscle pathology
        in laminin-α2 chain-deficient congenital muscular dystrophy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Weakness of intercostal and accessory muscles results in progressive restriction
        of the chest wall, decreased lung volume, reduced alveolar gas exchange, and eventually
        restrictive respiratory insufficiency.
      explanation: The clinical mechanistic review explicitly states the respiratory causal
        sequence.
  - target: Impaired Respiratory Secretion Clearance
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Respiratory muscle weakness limits effective cough and secretion clearance.
    evidence:
    - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK97333/
      reference_title: LAMA2 Muscular Dystrophy - GeneReviews® - NCBI Bookshelf
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Poor secretion clearance resulting from weak cough leads to recurrent chest infection.
      explanation: The clinical chapter explicitly establishes impaired cough-mediated clearance
        as a cause of recurrent infection.
  evidence:
  - reference: PMID:31308722
    reference_title: Current understanding and treatment of cardiac and skeletal muscle pathology
      in laminin-α2 chain-deficient congenital muscular dystrophy.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Weakness of intercostal and accessory muscles results in progressive restriction
      of the chest wall, decreased lung volume, reduced alveolar gas exchange, and eventually
      restrictive respiratory insufficiency.
    explanation: The clinical mechanistic review explicitly states the respiratory causal sequence.
- name: Loss of Laminin-211 from the Schwann Cell Basal Lamina
  biological_scale: MOLECULAR
  description: Laminin-alpha2 in Schwann-cell basal lamina supports axonal sorting and myelin
    organization. Deficiency can disturb developmental myelination; variable human nerve pathology
    does not justify excluding superimposed demyelination or remyelination in all patients.
  cell_types:
  - preferred_term: Schwann cell
    term:
      id: CL:0002573
      label: Schwann cell
  downstream:
  - target: Peripheral Dysmyelination
    causal_link_type: DIRECT
    description: >-
      Without its basal-lamina ligand the Schwann cell cannot build normal compact myelin.
  evidence:
  - reference: PMID:8576559
    reference_title: "Demyelinating peripheral neuropathy in merosin-deficient congenital muscular dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Because the alpha 2 subunit is also expressed in S-merosin, found in Schwann cells, we have investigated whether peripheral nerve function is also affected in these patients."
    explanation: Establishes Schwann-cell expression of the alpha-2 chain, which is what this node reports as lost.
  - reference: PMID:31341277
    reference_title: "A mutation-independent approach for muscular dystrophy via upregulation of a modifier gene."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "MDC1A is caused by mutations in LAMA2 that lead to nonfunctional laminin-α2, which compromises the stability of muscle fibres and the myelination of peripheral nerves."
    explanation: States the peripheral-nerve myelination arm alongside the muscle arm.
- name: Peripheral Dysmyelination
  biological_scale: TISSUE
  conforms_to: "schwann_cell_myelin_maintenance#Dysmyelination and Segmental Demyelination of Peripheral Nerve"
  description: Peripheral myelin abnormalities accompany some cases, with variable motor conduction
    slowing. A mildly affected partial-deficiency patient had biopsy evidence of abnormal myelinogenesis;
    that case cannot define every severe congenital neuropathy. Human functional contribution
    is usually limited compared with the marked peripheral nerve phenotype of some mouse models.
  cell_types:
  - preferred_term: Schwann cell
    term:
      id: CL:0002573
      label: Schwann cell
  biological_processes:
  - preferred_term: myelination in peripheral nervous system
    term:
      id: GO:0022011
      label: myelination in peripheral nervous system
    modifier: DECREASED
  locations:
  - preferred_term: peripheral nervous system
    term:
      id: UBERON:0000010
      label: peripheral nervous system
  notes: >-
    Conformance is declared against the dysmyelination node of `schwann_cell_myelin_maintenance`
    rather than against its trigger node, deliberately. That module scopes its trigger to
    Schwann-cell myelin gene dosage and structural lesions (PMP22, MPZ, GJB1, EGR2, the CMT4
    trafficking genes); the lesion here is an extracellular matrix ligand the Schwann cell
    secretes for its own basal lamina, which is not one of them. What conforms is the
    tissue-level outcome, dysmyelinated peripheral nerve with a remodeling signature and
    conduction slowing, and it conforms with the module's own scope boundary intact, since the
    primary lesion is Schwann-cell-derived rather than an immune attack from outside the cell.
  evidence:
  - reference: PMID:8576559
    reference_title: "Demyelinating peripheral neuropathy in merosin-deficient congenital muscular dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All but two of the 10 merosin-deficient cases had reduced motor nerve conduction, whereas all the merosin-positive cases had normal results."
    explanation: Ties the conduction slowing specifically to merosin deficiency rather than to congenital muscular dystrophy in general.
  - reference: PMID:12661054
    reference_title: "Dysmyelinating sensory-motor neuropathy in merosin-deficient congenital muscular dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Nerve biopsy showed reduction of large myelinated fibers, short internodes, enlarged nodes, excessive variability of myelin thickness, tomacula, and uncompacted myelin, but no evidence of segmental demyelination, naked axons, or onion bulbs."
    explanation: These findings came from a mildly affected patient with partial muscle merosin
      deficiency; the absence of segmental demyelination in that case is not a disease-wide
      rule.
  - reference: PMID:12661054
    reference_title: "Dysmyelinating sensory-motor neuropathy in merosin-deficient congenital muscular dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Thus, in congenital muscular dystrophy, merosin expression may be dissociated in different tissues, and the neuropathy is sensory-motor and due to abnormal myelinogenesis."
    explanation: The authors interpret the neuropathy in this partial-deficiency case as abnormal
      myelinogenesis.
  - reference: PMID:32848593
    reference_title: "LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers, and Clinical Trial Readiness."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Mild, sensorimotor demyelinating neuropathy is commonly observed, but its contribution to muscle weakness is considered to be minimal in the human, while it plays a substantial role in mouse models of lama2 deficiency"
    explanation: Records the human-versus-mouse divergence in the neuropathy's functional weight, which the node reports.
- name: Loss of Laminin-211 at the Glia Limitans and CNS Vascular Basement Membranes
  biological_scale: MOLECULAR
  description: >-
    In the brain the alpha-2 chain is contributed by astrocyte foot processes at the glia
    limitans and the blood-brain barrier. Its loss therefore destabilises two distinct CNS
    basement-membrane compartments: the perivascular one, whose failure is the leading
    explanation for the white-matter signal change, and the pial one, whose failure permits
    cortical overmigration.
  cell_types:
  - preferred_term: astrocyte endfoot at the glia limitans
    term:
      id: CL:0000127
      label: astrocyte
  cellular_components:
  - preferred_term: CNS basement membrane
    term:
      id: GO:0005604
      label: basement membrane
  downstream:
  - target: Increased Cerebral White Matter Water Content
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Increased white-matter water is attributed provisionally to impaired blood-brain
      barrier filtration after laminin-alpha2 loss. Human MR measurements support increased
      water, while the permeability mechanism remains a hypothesis and alternative myelin-related
      contributions are unresolved.
    evidence:
    - reference: PMID:37182895
      reference_title: Brain MRI Abnormalities, Epilepsy and Intellectual Disability in LAMA2
        Related Dystrophy - a Genotype/Phenotype Correlation.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: One hypothesis is that white matter contains increased water content due to impaired
        selective filtration of blood-brain barrier caused by laminin-α2 deficiency [24, 34].
      explanation: This is the authors’ mechanistic hypothesis, not a direct human permeability
        experiment.
  - target: Pial Basement Membrane Assembly Failure
    causal_link_type: DIRECT
    description: >-
      The glia limitans is a laminin-dependent basement membrane, so withdrawal of its principal
      alpha chain is an assembly defect.
  evidence:
  - reference: PMID:32827036
    reference_title: "Cobblestone Malformation in LAMA2 Congenital Muscular Dystrophy (MDC1A)."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "In the brain, laminin α2 is expressed by astrocyte foot processes at the glia limitans and blood-brain barrier"
    explanation: This sentence summarizes prior CNS expression knowledge in the introduction
      to the human autopsy report.
- name: Increased Cerebral White Matter Water Content
  biological_scale: TISSUE
  description: MR spectroscopy and diffusion imaging in nine children with merosin-deficient
    CMD support increased free water in affected cerebral white matter. A leaky perivascular
    basement membrane is a proposed upstream explanation; the MRI signal alone does not demonstrate
    demyelination. Human autopsy can show marked MRI abnormalities without white-matter histopathology.
  locations:
  - preferred_term: cerebral hemisphere white matter
    term:
      id: UBERON:0002437
      label: cerebral hemisphere white matter
  evidence:
  - reference: PMID:15703311
    reference_title: 'Congenital muscular dystrophy with merosin deficiency: 1H MR spectroscopy
      and diffusion-weighted MR imaging.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: ADC mapping and (1)H MR spectroscopy reveal abnormally high free-water concentrations
      in the WM of patients with merosin-deficient CMD.
    explanation: Direct human MR measurements in nine children support increased white-matter
      water content.
- name: Pial Basement Membrane Assembly Failure
  biological_scale: TISSUE
  conforms_to: "pial_basement_membrane_radial_glial_endfoot_failure#Pial Basement Membrane Assembly Failure"
  description: >-
    In a minority of patients the pial basement membrane is not merely thinner but focally
    breached. Autopsy of an MDC1A brain showed focal disruptions of the glia limitans with
    abnormal cortical lamination and arrested cerebellar granule cell migration, the classic
    substrate of a cobblestone malformation, here arising from loss of a structural laminin
    rather than from defective dystroglycan glycosylation. The module conformance is exact in
    mechanism: this entry substitutes an absent laminin ligand where the dystroglycanopathies
    substitute an unglycosylated receptor, and both converge on the same boundary failure.
  biological_processes:
  - preferred_term: pial basement membrane assembly
    term:
      id: GO:0070831
      label: basement membrane assembly
    modifier: DECREASED
  downstream:
  - target: Aberrant Cortical Neuronal Migration
    causal_link_type: DIRECT
    description: >-
      A breached glia limitans permits neurons and glia to overmigrate past the cortical surface,
      producing the cobblestone and polymicrogyric cortex.
  evidence:
  - reference: PMID:32827036
    reference_title: "Cobblestone Malformation in LAMA2 Congenital Muscular Dystrophy (MDC1A)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Brain histopathology included focal disruptions of the glia limitans associated with abnormal cerebral cortical lamination or arrested cerebellar granule cell migration."
    explanation: Directly demonstrates the pial boundary breach and its migration consequence in human MDC1A neuropathology.
- name: Aberrant Cortical Neuronal Migration
  biological_scale: TISSUE
  description: Loss of pial boundary integrity permits abnormal cortical neuronal migration
    and lamination. Human pathology supports this route to cobblestone malformation and related
    cortical abnormalities. The authors propose that such abnormalities can underlie seizures
    or intellectual disability in a subset, but one autopsied patient had normal cognition and
    no seizures despite cobblestone pathology. Seizures also occur without a visible cortical
    anomaly.
  downstream:
  - target: Seizures
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Disordered cortical migration and lamination can contribute to this clinical
      outcome; risk is variable and the intermediate circuit changes are not established.
    evidence:
    - reference: PMID:32827036
      reference_title: Cobblestone Malformation in LAMA2 Congenital Muscular Dystrophy (MDC1A).
      supports: SUPPORT
      evidence_source: OTHER
      snippet: These abnormalities, whether subtle or overt, likely underlie the seizures and
        intellectual disability that occur in a subset of patients with MDC1A.
      explanation: This explicit causal hypothesis follows the human cortical pathology findings;
        it is stronger than co-occurrence but remains qualified.
  - target: Intellectual disability
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Disordered cortical migration and lamination can contribute to this clinical
      outcome; risk is variable and the intermediate circuit changes are not established.
    evidence:
    - reference: PMID:32827036
      reference_title: Cobblestone Malformation in LAMA2 Congenital Muscular Dystrophy (MDC1A).
      supports: SUPPORT
      evidence_source: OTHER
      snippet: These abnormalities, whether subtle or overt, likely underlie the seizures and
        intellectual disability that occur in a subset of patients with MDC1A.
      explanation: This explicit causal hypothesis follows the human cortical pathology findings;
        it is stronger than co-occurrence but remains qualified.
  - target: Cobblestone cortical malformation
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Overmigration through focal glia-limitans breaches creates abnormal cortical
      lamination.
    evidence:
    - reference: PMID:32827036
      reference_title: Cobblestone Malformation in LAMA2 Congenital Muscular Dystrophy (MDC1A).
      supports: SUPPORT
      evidence_source: OTHER
      snippet: In MDC1A, the loss of laminin α2 leads to loss of integrity of the glia limitans
        BM and over-migration of neurons through glia limitans defects in the cerebral cortex
        or failed migration of granule cell neurons in the cerebellum.
      explanation: The authors interpret human histology in terms of boundary failure and abnormal
        neuronal migration.
  - target: Polymicrogyria
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Abnormal cortical migration and organization can produce polymicrogyric patterns,
      which can overlap radiologically with cobblestone malformation.
    evidence:
    - reference: PMID:32827036
      reference_title: Cobblestone Malformation in LAMA2 Congenital Muscular Dystrophy (MDC1A).
      supports: SUPPORT
      evidence_source: OTHER
      snippet: In MDC1A, the loss of laminin α2 leads to loss of integrity of the glia limitans
        BM and over-migration of neurons through glia limitans defects in the cerebral cortex
        or failed migration of granule cell neurons in the cerebellum.
      explanation: The authors interpret human histology in terms of boundary failure and abnormal
        neuronal migration.
  evidence:
  - reference: PMID:32827036
    reference_title: Cobblestone Malformation in LAMA2 Congenital Muscular Dystrophy (MDC1A).
    supports: SUPPORT
    evidence_source: OTHER
    snippet: In MDC1A, the loss of laminin α2 leads to loss of integrity of the glia limitans
      BM and over-migration of neurons through glia limitans defects in the cerebral cortex
      or failed migration of granule cell neurons in the cerebellum.
    explanation: The authors interpret human histology in terms of boundary failure and abnormal
      neuronal migration.
  - reference: PMID:32827036
    reference_title: Cobblestone Malformation in LAMA2 Congenital Muscular Dystrophy (MDC1A).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Brain histopathology included focal disruptions of the glia limitans associated
      with abnormal cerebral cortical lamination or arrested cerebellar granule cell migration.
    explanation: Directly demonstrates the pial boundary breach and its migration consequence
      in human MDC1A neuropathology.
- name: Loss of Myocardial Laminin-211 Support
  biological_scale: TISSUE
  description: Laminin-211 is a myocardial extracellular-matrix component. Its deficiency is
    a proposed contributor to the ventricular dysfunction observed in some patients, but cardiac
    model phenotypes vary and the human pathway has not been directly established.
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:31308722
    reference_title: Current understanding and treatment of cardiac and skeletal muscle pathology
      in laminin-α2 chain-deficient congenital muscular dystrophy.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: As laminin-211 is a major component of the myocardial ECM, it is likely that its
      loss will have important implications for cardiac physiology.
    explanation: The review proposes a myocardial ECM mechanism; the intermediate cause of human
      ventricular dysfunction remains uncertain.
  downstream:
  - target: Abnormal left ventricular function
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Loss of myocardial matrix support is a proposed contributor to ventricular
      dysfunction; the relevant cellular intermediates and penetrance remain uncertain.
    evidence:
    - reference: PMID:31308722
      reference_title: Current understanding and treatment of cardiac and skeletal muscle pathology
        in laminin-α2 chain-deficient congenital muscular dystrophy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: As laminin-211 is a major component of the myocardial ECM, it is likely that
        its loss will have important implications for cardiac physiology.
      explanation: The review proposes a myocardial ECM mechanism; the intermediate cause of
        human ventricular dysfunction remains uncertain.
- name: Impaired Respiratory Secretion Clearance
  biological_scale: TISSUE
  description: Weak cough impairs airway secretion clearance and predisposes to recurrent chest
    infection. This route is distinct from aspiration-related infection.
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK97333/
    reference_title: LAMA2 Muscular Dystrophy - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Poor secretion clearance resulting from weak cough leads to recurrent chest infection.
    explanation: The clinical chapter explicitly establishes impaired cough-mediated clearance
      as a cause of recurrent infection.
  downstream:
  - target: Recurrent respiratory infections
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Retained airway secretions increase the risk of recurrent infection.
    evidence:
    - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK97333/
      reference_title: LAMA2 Muscular Dystrophy - GeneReviews® - NCBI Bookshelf
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Poor secretion clearance resulting from weak cough leads to recurrent chest infection.
      explanation: The clinical chapter explicitly establishes impaired cough-mediated clearance
        as a cause of recurrent infection.
phenotypes:
- name: Neonatal hypotonia
  category: Neuromuscular
  description: Profound hypotonia can be present neonatally, with reduced spontaneous movements
    and weak cry. Early-onset hypotonia is a hallmark, but the proportion with any symptom in
    the first week does not separately measure neonatal hypotonia.
  phenotype_term:
    preferred_term: Neonatal hypotonia
    term:
      id: HP:0001319
      label: Neonatal hypotonia
  evidence:
  - reference: PMID:22675738
    reference_title: "LAMA2 Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "MDC1A is typically characterized by neonatal profound hypotonia, poor spontaneous movements, and respiratory failure."
    explanation: GeneReviews names neonatal profound hypotonia as a defining manifestation.
- name: Axial muscle weakness
  category: Neuromuscular
  frequency: VERY_FREQUENT
  description: Severe axial weakness, including head and trunk flexors, is prominent in congenital
    disease; proximal limb weakness is recorded separately.
  phenotype_term:
    preferred_term: Axial muscle weakness
    term:
      id: HP:0003327
      label: Axial muscle weakness
  evidence:
  - reference: PMID:37476021
    reference_title: "LAMA2-Related Muscular Dystrophy Across the Life Span: A Cross-sectional Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Axial and proximal muscle weakness was most pronounced."
    explanation: States the weakness distribution directly.
  - reference: PMID:32848593
    reference_title: "LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers, and Clinical Trial Readiness."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Clinical hallmarks are early-onset severe hypotonia, axial weakness, inability to achieve independent ambulation, and elevated creatine kinase (CK) levels, commonly >1,000 IU/L"
    explanation: Lists axial weakness among the defining clinical hallmarks.
  sequelae:
  - target: Inability to walk
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Severe axial and proximal weakness can prevent independent ambulation.
    evidence:
    - reference: PMID:32848593
      reference_title: 'LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers,
        and Clinical Trial Readiness.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Muscle atrophy and severe weakness typically prevent independent ambulation.
      explanation: The clinical review explicitly links muscle loss and weakness to failure
        of walking.
  - target: Delayed gross motor development
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: The congenital motor deficit delays acquisition of postural and locomotor milestones.
  - target: Hyperlordosis
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Severe neck flexor weakness can lead to cervical lordosis in adolescence; this
      explains a specific component of the broader lordosis phenotype.
    evidence:
    - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK97333/
      reference_title: LAMA2 Muscular Dystrophy - GeneReviews® - NCBI Bookshelf
      supports: SUPPORT
      evidence_source: OTHER
      snippet: This weakness may progress to a severe cervical lordosis in late adolescence,
        affecting the capacity to swallow and increasing the risk of food aspiration.
      explanation: The preceding chapter sentence identifies neck flexor weakness; the consequence
        is specifically cervical lordosis.
- name: Inability to walk
  category: Neuromuscular
  frequency: VERY_FREQUENT
  subtype: Complete deficiency
  description: Independent walking was attained by only 1 of 42 patients classified as completely
    merosin deficient in the UK cohort. In the Chinese clinical LAMA2-CMD cohort, 18 of 98 patients
    older than 18 months walked independently; those clinical categories are not identical to
    complete deficiency. Walking may subsequently be lost.
  phenotype_term:
    preferred_term: Inability to walk
    term:
      id: HP:0002540
      label: Inability to walk
  evidence:
  - reference: PMID:34281576
    reference_title: "Natural history and genetic study of LAMA2-related muscular dystrophy in a large Chinese cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Head control, independent sitting and ambulation were achieved in 76.3%, 92.6% and 18.4% of LAMA2-CMD patients at median ages of 6.0 months (range 2.0-36.0 months), 11.0 months (range 6.0-36.0 months), and 27.0 months (range 18.0-84.0 months), respectively."
    explanation: The walking denominator is 98 clinical LAMA2-CMD patients older than 18 months,
      not all 116 CMD patients or an immunostaining-defined complete-deficiency group.
  - reference: PMID:32910545
    reference_title: "LAMA2-related muscular dystrophy: Natural history of a large pediatric cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "One CD and two PD subjects achieved independent ambulation."
    explanation: One of 42 patients classified as completely deficient attained independent
      walking; classification was not based on biopsy in every participant.
- name: Delayed gross motor development
  category: Neuromuscular
  frequency: VERY_FREQUENT
  description: >-
    Motor milestones are delayed or never attained. Head control and independent sitting are
    achieved by most, but late; ambulation usually is not.
  phenotype_term:
    preferred_term: Delayed gross motor development
    term:
      id: HP:0002194
      label: Delayed gross motor development
  evidence:
  - reference: PMID:32910545
    reference_title: 'LAMA2-related muscular dystrophy: Natural history of a large pediatric
      cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: All patients had motor delay.
    explanation: Direct observation in the UK cohort of 42 complete- and four partial-deficiency
      patients.
- name: Elevated serum creatine kinase
  category: Biochemical
  frequency: VERY_FREQUENT
  description: CK is markedly elevated in congenital disease, often above 1,000 IU/L. The UK
    complete-deficiency group had values of 394–36,000 IU/L; values tend to decline with age.
    CK is a biochemical readout of muscle injury, not a clinical consequence requiring a causal
    phenotype arrow.
  phenotype_term:
    preferred_term: Elevated circulating creatine kinase activity
    term:
      id: HP:0003236
      label: Elevated circulating creatine kinase activity
  reports_on:
  - target: Myofibre Degeneration, Necrosis and Apoptosis
    relationship: READOUT_OF
  evidence:
  - reference: PMID:32848593
    reference_title: "LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers, and Clinical Trial Readiness."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Clinical hallmarks are early-onset severe hypotonia, axial weakness, inability to achieve independent ambulation, and elevated creatine kinase (CK) levels, commonly >1,000 IU/L"
    explanation: Gives the characteristic magnitude of the creatine kinase elevation.
  - reference: PMID:39213089
    reference_title: "A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "CK level was available for 13 patients and was elevated in all of them"
    explanation: Records universal elevation in the registry cohort, supporting the VERY_FREQUENT band.
- name: Joint contracture
  category: Musculoskeletal
  frequency: VERY_FREQUENT
  description: Flexion contractures commonly affect large joints and fingers, can present in
    infancy, and often progress. Longitudinal UK measurements demonstrated increasing elbow
    and knee contractures; a uniform linear course at every joint is not established.
  phenotype_term:
    preferred_term: Flexion contracture
    term:
      id: HP:0001371
      label: Flexion contracture
  sequelae:
  - target: Inability to walk
  - target: Motor regression
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Progressive contractures can impede motor function and contribute to loss of
      skills. This does not establish that every regression event is contracture-driven.
    evidence:
    - reference: PMID:32848593
      reference_title: 'LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers,
        and Clinical Trial Readiness.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Severe, progressive proximal and distal joints’ contractures, in upper and lower
        limbs, can be present from as early as birth (Prandini et al., 2004), with a considerable
        detrimental effect on motor function.
      explanation: The review establishes adverse motor effects; the Chinese cohort separately
        documents regression during rapid contracture progression.
  evidence:
  - reference: PMID:32848593
    reference_title: "LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers, and Clinical Trial Readiness."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Progressive joint contractures, respiratory insufficiency, and scoliosis are observed in almost all patients."
    explanation: Supports the VERY_FREQUENT band for contractures.
  - reference: PMID:39213089
    reference_title: "A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In four patients with CMD, contractures were reported as the initially presenting symptom."
    explanation: Documents contracture as a presenting rather than late feature.
- name: Spinal rigidity
  category: Musculoskeletal
  description: Spinal rigidity occurs in congenital and milder LAMA2 disease. It was recorded
    in 13 of 42 complete-deficiency and two of four partial-deficiency UK patients; the Dutch
    life-span cohort reported it in all 27 participants.
  phenotype_term:
    preferred_term: Spinal rigidity
    term:
      id: HP:0003306
      label: Spinal rigidity
  evidence:
  - reference: PMID:32910545
    reference_title: 'LAMA2-related muscular dystrophy: Natural history of a large pediatric
      cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Neck rigidity was reported in 21 patients (20 CD and one PD), spine rigidity in
      15 (13 CD and two PD), and lordosis in 12 (10 CD and two PD).
    explanation: The UK cohort separates neck, spine and lordosis findings and complete from
      partial deficiency.
- name: Scoliosis
  category: Musculoskeletal
  frequency: FREQUENT
  description: Scoliosis often develops or progresses during childhood in severe congenital
    disease. The UK report gives 32 affected complete-deficiency patients in its abstract and
    33 in the results, out of 42; nine underwent spinal surgery. The Chinese congenital cohort
    reported 45/111 (40.5%). Ambulation does not categorically exclude scoliosis.
  phenotype_term:
    preferred_term: Scoliosis
    term:
      id: HP:0002650
      label: Scoliosis
  evidence:
  - reference: PMID:32910545
    reference_title: "LAMA2-related muscular dystrophy: Natural history of a large pediatric cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Thirty-two CD and one PD patient developed scoliosis, nine underwent spinal surgery."
    explanation: The abstract reports 32/42 complete-deficiency patients, while the results
      report 33/42; this internal discrepancy is retained explicitly rather than silently resolved.
  sequelae:
  - target: Respiratory insufficiency due to muscle weakness
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Scoliosis may worsen thoracic restriction and compress airways.
    evidence:
    - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK97333/
      reference_title: LAMA2 Muscular Dystrophy - GeneReviews® - NCBI Bookshelf
      supports: SUPPORT
      evidence_source: OTHER
      snippet: It is often slowly progressive and may contribute to respiratory insufficiency
        due to thoracic restriction and airway compression.
      explanation: The antecedent in the full chapter is scoliosis.
- name: Restrictive ventilatory defect
  category: Respiratory
  frequency: VERY_FREQUENT
  description: 'Restrictive impairment is frequent in tested patients: 17/20 in the Dutch mixed
    life-span cohort had FVC below 80% predicted, and 23/25 complete-deficiency UK patients
    had FVC below 60%. Intercostal and accessory muscle weakness is important; prominent diaphragm
    dysfunction was not found in the Dutch cohort. Twenty-two UK complete-deficiency patients
    required nocturnal ventilation.'
  phenotype_term:
    preferred_term: Restrictive ventilatory defect
    term:
      id: HP:0002091
      label: Restrictive ventilatory defect
  evidence:
  - reference: PMID:37476021
    reference_title: "LAMA2-Related Muscular Dystrophy Across the Life Span: A Cross-sectional Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Respiratory function was impaired in 85% of patients without prominent diaphragm dysfunction and was independent of age."
    explanation: Gives the 85% frequency supporting the VERY_FREQUENT band and the absence of diaphragmatic predominance.
  - reference: PMID:32910545
    reference_title: "LAMA2-related muscular dystrophy: Natural history of a large pediatric cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Twenty-two CD required nocturnal noninvasive ventilation (median age 11.7 years)."
    explanation: Documents the ventilatory support requirement and its timing.
- name: Recurrent respiratory infections
  category: Respiratory
  frequency: FREQUENT
  description: >-
    Aspiration and weak cough produce recurrent chest infections that require frequent
    hospitalisation, and severe pneumonia is the leading cause of death.
  phenotype_term:
    preferred_term: Recurrent respiratory infections
    term:
      id: HP:0002205
      label: Recurrent respiratory infections
  evidence:
  - reference: PMID:22675738
    reference_title: "LAMA2 Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Failure to thrive, gastroesophageal reflux, aspiration, and recurrent chest infections necessitating frequent hospitalizations are common."
    explanation: GeneReviews names recurrent chest infection as a common complication.
  - reference: PMID:34281576
    reference_title: "Natural history and genetic study of LAMA2-related muscular dystrophy in a large Chinese cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Twenty-four LAMA2-related muscular dystrophy patients died, mostly due to severe pneumonia."
    explanation: Establishes pneumonia as the dominant cause of death.
  - reference: PMID:34281576
    reference_title: Natural history and genetic study of LAMA2-related muscular dystrophy in
      a large Chinese cohort.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In total, 58.9% (63/107) of LAMA2-CMD and 35.7% (5/14) of LGMDR23 patients had
      a history of recurrent respiratory infection, mainly at ages of 0–3 years and 6–15 years
      (Fig.
    explanation: Recurrent respiratory infection was recorded in 63/107 clinical LAMA2-CMD patients;
      the broader cohort includes a separately reported LGMDR23 group.
- name: Feeding difficulties
  category: Gastrointestinal
  frequency: FREQUENT
  description: Feeding impairment includes chewing difficulty, inefficient oral transfer and
    dysphagia. In the UK cohort 19 complete-deficiency and one partial-deficiency patients received
    gastrostomy; the observed median age was five years, whereas the survival-analysis estimate
    was 10.9 years. These intervention counts are not feeding-difficulty prevalence.
  phenotype_term:
    preferred_term: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
  sequelae:
  - target: Failure to thrive
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Inefficient chewing and swallowing reduce nutritional intake and contribute
      to poor weight gain.
    evidence:
    - reference: PMID:31308722
      reference_title: Current understanding and treatment of cardiac and skeletal muscle pathology
        in laminin-α2 chain-deficient congenital muscular dystrophy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Feeding difficulties, swallowing abnormalities, and difficulty in chewing all
        contribute to poor weight gain in affected children.
      explanation: The clinical review explicitly attributes poor growth to feeding dysfunction.
  evidence:
  - reference: PMID:22675738
    reference_title: "LAMA2 Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "As disease progresses, facial muscle weakness, temporomandibular joint contractures, and macroglossia may further impair feeding and can affect speech."
    explanation: States the mechanisms that aggravate feeding difficulty over the course of the disease.
  - reference: PMID:32910545
    reference_title: "LAMA2-related muscular dystrophy: Natural history of a large pediatric cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Nineteen CD and one PD patient required gastrostomy insertion for failure to thrive and/or unsafe swallow (median age 10.9 years)."
    explanation: The quoted 10.9 years is a time-to-event estimate; the observed median gastrostomy
      age was five years. Gastrostomy requirement does not measure all feeding impairment.
- name: Failure to thrive
  category: Growth
  description: Poor growth and undernutrition can complicate inefficient feeding and dysphagia.
    In a selected series of 14 severely affected nonambulant children, 12 were below the third
    weight centile; gastrostomy improved weight gain in five treated children. Some registry
    patients remained underweight despite tube feeding, which does not establish a separate
    metabolic cause.
  phenotype_term:
    preferred_term: Failure to thrive
    term:
      id: HP:0001508
      label: Failure to thrive
  evidence:
  - reference: PMID:10332004
    reference_title: Feeding problems in merosin deficient congenital muscular dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Twelve of the 14 children were below the 3rd centile for weight.
    explanation: Documents poor growth in a selected severe pediatric feeding study, not a population
      prevalence.
  - reference: PMID:10332004
    reference_title: Feeding problems in merosin deficient congenital muscular dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: As a result of the study five children had a gastrostomy, which stopped the chest
      infections and improved weight gain.
    explanation: Within-series improvement supports feeding-related morbidity; it is not a controlled
      treatment effect.
- name: Gastroesophageal reflux
  category: Gastrointestinal
  description: >-
    Reflux contributes to aspiration risk and is one of the reasons feeding safety is assessed
    routinely.
  phenotype_term:
    preferred_term: Gastroesophageal reflux
    term:
      id: HP:0002020
      label: Gastroesophageal reflux
  evidence:
  - reference: PMID:10332004
    reference_title: Feeding problems in merosin deficient congenital muscular dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Six of eight children who had pH monitoring also had gastro-oesophageal reflux.
    explanation: Six of eight selected tested children had reflux; this is not a denominator
      for all MDC1A patients.
  sequelae:
  - target: Aspiration
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Reflux can increase aspiration risk.
    evidence:
    - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK97333/
      reference_title: LAMA2 Muscular Dystrophy - GeneReviews® - NCBI Bookshelf
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Swallowing difficulties and gastroesophageal reflux may increase the risk of
        aspiration.
      explanation: The full GeneReviews chapter explicitly attributes increased aspiration risk
        to reflux and dysphagia.
- name: Macroglossia
  category: Craniofacial
  description: Macroglossia can impair oral feeding. It was present in 7/27 participants in
    the Dutch mixed congenital-to-limb-girdle cohort; that estimate is not specific to completely
    merosin-deficient children.
  phenotype_term:
    preferred_term: Macroglossia
    term:
      id: HP:0000158
      label: Macroglossia
  evidence:
  - reference: PMID:37476021
    reference_title: "LAMA2-Related Muscular Dystrophy Across the Life Span: A Cross-sectional Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Seven of 27 patients had a macroglossia, a high arched palate was found in 17/27
      patients, while 13/27 patients had an elongated face.
    explanation: The direct cohort observation replaces an introductory review statement; the
      sample spans the broader LAMA2 spectrum.
  sequelae:
  - target: Feeding difficulties
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Impaired oral mechanics can reduce safe and efficient feeding.
    evidence:
    - reference: PMID:22675738
      reference_title: LAMA2 Muscular Dystrophy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: As disease progresses, facial muscle weakness, temporomandibular joint contractures,
        and macroglossia may further impair feeding and can affect speech.
      explanation: GeneReviews explicitly identifies these contributors to progressive feeding
        impairment.
  - target: Oropharyngeal dysphagia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Facial weakness or tongue enlargement may worsen the oral phase of swallowing.
    evidence:
    - reference: PMID:32848593
      reference_title: 'LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers,
        and Clinical Trial Readiness.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Macroglossia and facial weakness might further contribute to the defective oral
        phase in LAMA2-RD patients.
      explanation: The review explicitly proposes contributors to the oral component of dysphagia;
        it does not establish every pharyngeal intermediate.
- name: Ophthalmoparesis
  category: Ophthalmologic
  frequency: FREQUENT
  description: Progressive partial limitation of extraocular movements, particularly upward
    gaze, may become evident from early childhood. Eighteen of 42 complete-deficiency UK patients
    had ophthalmoparesis; complete paralysis is not established.
  phenotype_term:
    preferred_term: Ophthalmoparesis
    term:
      id: HP:0000597
      label: Ophthalmoparesis
  evidence:
  - reference: PMID:32910545
    reference_title: 'LAMA2-related muscular dystrophy: Natural history of a large pediatric
      cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Facial weakness and ophtalmoparesis were observed in 21 and 18 CD patients, respectively,
      but in no PD.
    explanation: Direct complete-deficiency cohort evidence supports partial ocular paresis
      and the FREQUENT band.
  - reference: PMID:32848593
    reference_title: 'LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers, and
      Clinical Trial Readiness.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: A progressive limitation of extraocular movements, in particular of upward gaze,
      is noted as early as at 2 years of age, with clear ophthalmoparesis in the horizontal
      and upwards direction becoming more evident by the end of the first decade.
    explanation: The review describes progression and onset in childhood.
- name: Hyperintensity of cerebral white matter on MRI
  category: Neurologic
  frequency: VERY_FREQUENT
  description: Diffuse periventricular and subcortical T2/FLAIR hyperintensity is very frequent
    after infancy but can be absent or subtle in young infants and some milder cases. Clear
    abnormalities were observed from three months in the Swiss cohort. Signal change is an imaging
    readout of increased white-matter water content; it does not itself prove demyelination
    or predict intellectual disability.
  phenotype_term:
    preferred_term: Hyperintensity of cerebral white matter on MRI
    term:
      id: HP:0030890
      label: Hyperintensity of cerebral white matter on MRI
  reports_on:
  - target: Increased Cerebral White Matter Water Content
    relationship: READOUT_OF
  evidence:
  - reference: PMID:32848593
    reference_title: "LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers, and Clinical Trial Readiness."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Characteristic brain white matter (WM) hypointensity on T1 magnetic resonance imaging (MRI), and increased T2 signal in the periventricular and subcortical WM, are invariably observed in most patients older than 6 months"
    explanation: Establishes the imaging finding and its near-universal presence beyond six months, supporting the VERY_FREQUENT band.
  - reference: PMID:39213089
    reference_title: "A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The youngest age at which MRI showed clear white matter changes was 3 months."
    explanation: Records the earliest age at which the finding was demonstrable in this cohort.
- name: Cobblestone cortical malformation
  category: Neurologic
  description: Cobblestone cortical malformation is variably visible on MRI, often parieto-occipital.
    Six of 12 re-reviewed Swiss scans showed it, whereas a Brazilian series found one among
    52 patients. These differently assessed cohorts do not establish a single population frequency.
    Human autopsy demonstrated subtle malformation despite structurally unremarkable clinical
    MRI.
  phenotype_term:
    preferred_term: Cobblestone cortical malformation
    term:
      id: HP:0007260
      label: Type II lissencephaly
  evidence:
  - reference: PMID:39213089
    reference_title: "A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In 7 patients, additional cortical abnormalities were found: parieto-occipital cobblestone malformation (six patients) and/or polymicrogyria (three patients)."
    explanation: Documents the cobblestone malformation and its parieto-occipital distribution.
  - reference: PMID:32827036
    reference_title: "Cobblestone Malformation in LAMA2 Congenital Muscular Dystrophy (MDC1A)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These cases demonstrate that cobblestone malformation may be an important manifestation of the brain pathology in MDC1A and can be present even when patients have a structurally normal brain MRI."
    explanation: Selected human cases show that clinical MRI can miss subtle cobblestone pathology,
      without quantifying its frequency in unselected MDC1A.
- name: Polymicrogyria
  category: Neurologic
  description: Polymicrogyria is often occipital but can involve temporal or frontal cortex.
    It may overlap radiologically with cobblestone malformation. The 19.2% Brazilian figure
    concerns all cortical malformations, not polymicrogyria alone; an individual with extensive
    occipital malformation developed focal epilepsy and regression.
  phenotype_term:
    preferred_term: Polymicrogyria
    term:
      id: HP:0002126
      label: Polymicrogyria
  evidence:
  - reference: PMID:37182895
    reference_title: "Brain MRI Abnormalities, Epilepsy and Intellectual Disability in LAMA2 Related Dystrophy - a Genotype/Phenotype Correlation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "10 patients (19.2%) presented with cortical malformations (polymicrogyria, lissencephaly-pachygyria, and cobblestone)"
    explanation: This establishes polymicrogyria within the observed cortical abnormalities;
      10/52 is the aggregate malformation count and cannot serve as polymicrogyria prevalence.
  - reference: PMID:18406646
    reference_title: "LAMA2 stop-codon mutation: merosin-deficient congenital muscular dystrophy with occipital polymicrogyria, epilepsy and psychomotor regression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "When 6.9 years old, she developed focal occipital seizures and absence-like status when awake, with probable relation to an extensive bilateral occipital micropolygyria."
    explanation: Documents occipital polymicrogyria with focal seizures in a patient with a homozygous LAMA2 stop-codon variant.
- name: Seizures
  category: Neurologic
  frequency: OCCASIONAL
  description: Seizures include focal epilepsy and febrile seizures. In the Chinese clinical
    congenital group 9/116 had epilepsy and two had febrile seizures, yielding the reported
    11/116 (9.5%) seizure figure; the LGMDR23 group had three epilepsy and two febrile-seizure
    cases among 14. These are clinical subtype comparisons, not complete-versus-partial staining
    denominators.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:34281576
    reference_title: "Natural history and genetic study of LAMA2-related muscular dystrophy in a large Chinese cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Seizures occurred in 35.7% of LGMDR23 and 9.5% of LAMA2-CMD patients."
    explanation: The stated seizure percentages include febrile seizures as well as epilepsy
      and refer to clinical onset subgroups.
  - reference: PMID:32848593
    reference_title: "LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers, and Clinical Trial Readiness."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Seizures, usually responsive to antiepileptic medications in the absence of an underlying cortical anomaly, are observed in up to ~30% of patients"
    explanation: Gives the upper bound of reported frequency and the response to first-line treatment.
- name: Intellectual disability
  category: Neurologic
  frequency: OCCASIONAL
  description: Intellectual disability affects a minority and is associated with cortical malformations
    in some cohorts. The Brazilian series reported 8/52 affected, including seven nonambulant
    patients and one ambulant patient with autism. Normal cognition is compatible with marked
    white-matter signal change or even cobblestone pathology; not every cohort used formal cognitive
    testing.
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: PMID:37182895
    reference_title: "Brain MRI Abnormalities, Epilepsy and Intellectual Disability in LAMA2 Related Dystrophy - a Genotype/Phenotype Correlation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 10 patients (19.2%) presented with cortical malformations (polymicrogyria, lissencephaly-pachygyria,
      and cobblestone),10 patients (19.2%) presented with epilepsy, and 8 (15.4%) had intellectual
      disability.
    explanation: The 52-patient cohort includes both severe and ambulant phenotypes; this is
      not a severe-only denominator.
  - reference: PMID:39213089
    reference_title: "A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Usually, cognitive abilities of patients are in the normal range"
    explanation: Establishes that normal cognition is the rule, which is why this phenotype is banded as occasional rather than frequent.
- name: Decreased motor nerve conduction velocity
  category: Neurologic
  frequency: FREQUENT
  description: >-
    Slowed motor conduction is the electrophysiological signature of the dysmyelinating
    neuropathy and separates merosin-deficient from merosin-positive congenital muscular
    dystrophy. Sensory studies are typically less affected. Note that it is not invariable in
    every series.
  phenotype_term:
    preferred_term: Decreased motor nerve conduction velocity
    term:
      id: HP:0003431
      label: Decreased motor nerve conduction velocity
  reports_on:
  - target: Peripheral Dysmyelination
    relationship: READOUT_OF
  evidence:
  - reference: PMID:8576559
    reference_title: "Demyelinating peripheral neuropathy in merosin-deficient congenital muscular dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All but two of the 10 merosin-deficient cases had reduced motor nerve conduction, whereas all the merosin-positive cases had normal results."
    explanation: Gives the frequency and the specificity of the finding to merosin deficiency.
  - reference: PMID:8576559
    reference_title: "Demyelinating peripheral neuropathy in merosin-deficient congenital muscular dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Sensory nerve studies showed no difference between the two groups."
    explanation: Supports the motor-predominant electrophysiological picture described here.
  - reference: PMID:32910545
    reference_title: 'LAMA2-related muscular dystrophy: Natural history of a large pediatric
      cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Six out of 13 CD patients showed mildly reduced conduction velocities for age (in
      ulnar or peroneal motor nerves).
    explanation: The later tested UK subgroup supports variable motor conduction slowing, rather
      than universal neuropathy.
- name: Increased endomysial connective tissue
  category: Histopathologic
  description: >-
    Marked endomysial connective-tissue increase on muscle biopsy, alongside wide variation in
    fibre size and scattered necrotic and regenerating fibres. This triad was part of the original
    morphological definition of congenital muscular dystrophy.
  phenotype_term:
    preferred_term: Increased endomysial connective tissue
    term:
      id: HP:0100297
      label: Increased endomysial connective tissue
  evidence:
  - reference: PMID:7550355
    reference_title: "Mutations in the laminin alpha 2-chain gene (LAMA2) cause merosin-deficient congenital muscular dystrophy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Histological changes seen in muscle biopsies consist of large variations in muscle fibre size, a few necrotic and regenerating fibres and a marked increase in endomysial collagen tissue."
    explanation: This introductory description summarizes congenital muscular dystrophy histology;
      it does not provide an MDC1A-specific biopsy prevalence.
- name: Abnormal left ventricular function
  category: Cardiovascular
  frequency: OCCASIONAL
  description: Mild left ventricular systolic dysfunction can occur. In the Dutch mixed life-span
    cohort 3/21 had reduced ejection fraction and 25% of those assessed had abnormal global
    longitudinal strain. Three UK patients had persistent mild left ventricular dysfunction;
    the separate seven-patient combined cardiac count includes rhythm and other findings.
  phenotype_term:
    preferred_term: Abnormal left ventricular function
    term:
      id: HP:0005162
      label: Abnormal left ventricular function
  evidence:
  - reference: PMID:37476021
    reference_title: "LAMA2-Related Muscular Dystrophy Across the Life Span: A Cross-sectional Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cardiac assessment revealed QRS fragmentation in 62%, abnormal left ventricular global longitudinal strain in 25%, and decreased left ventricular ejection fraction in 14% of patients."
    explanation: Quantifies the cardiac findings that motivate this phenotype and its frequency band.
  - reference: PMID:32910545
    reference_title: "LAMA2-related muscular dystrophy: Natural history of a large pediatric cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Mild persistent left ventricular dysfunction (atrial septum or inferior wall) was
      observed in three patients at age 9, 14 and 19 years, respectively.
    explanation: This isolates ventricular dysfunction from the combined count of all cardiac
      abnormalities.
- name: Pathologic fractures
  category: Musculoskeletal
  description: Eleven of 27 patients in the Dutch mixed LAMA2 life-span cohort had one or more
    fragility long-bone fractures. Fragility is supported, but recurrence in each patient and
    a congenital-only frequency are not. Reduced bone quality is documented; its precise determinants
    were not established.
  phenotype_term:
    preferred_term: Fragility fractures
    term:
      id: HP:0002756
      label: Pathologic fracture
  evidence:
  - reference: PMID:37476021
    reference_title: "LAMA2-Related Muscular Dystrophy Across the Life Span: A Cross-sectional Study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Eleven patients had experienced 1 or more fragility long bone fractures.
    explanation: The observed phenotype is fragility fracture, not necessarily recurrent fracture.
- name: Proximal muscle weakness
  category: Neuromuscular
  description: Proximal limb weakness accompanies axial weakness in both complete and partial
    deficiency.
  phenotype_term:
    preferred_term: Proximal muscle weakness
    term:
      id: HP:0003701
      label: Proximal muscle weakness
  evidence:
  - reference: PMID:32910545
    reference_title: 'LAMA2-related muscular dystrophy: Natural history of a large pediatric
      cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The distribution of limb weakness followed a proximodistal gradient in both CD
      and PD patients.
    explanation: Separately records the proximal component of the previously bundled weakness
      phenotype.
  sequelae:
  - target: Inability to walk
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Severe axial and proximal weakness can prevent independent ambulation.
    evidence:
    - reference: PMID:32848593
      reference_title: 'LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers,
        and Clinical Trial Readiness.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Muscle atrophy and severe weakness typically prevent independent ambulation.
      explanation: The clinical review explicitly links muscle loss and weakness to failure
        of walking.
  - target: Delayed gross motor development
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: The congenital motor deficit delays acquisition of postural and locomotor milestones.
- name: Facial muscle weakness
  category: Neuromuscular
  description: Facial weakness was recorded in 21/42 complete-deficiency UK patients and can
    interfere with oral feeding.
  phenotype_term:
    preferred_term: Weakness of facial musculature
    term:
      id: HP:0030319
      label: Weakness of facial musculature
  evidence:
  - reference: PMID:32910545
    reference_title: 'LAMA2-related muscular dystrophy: Natural history of a large pediatric
      cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Facial weakness and ophtalmoparesis were observed in 21 and 18 CD patients, respectively,
      but in no PD.
    explanation: Facial weakness was observed in 21 of 42 complete-deficiency UK patients,
      distinct from the 18 with ophthalmoparesis. No facial weakness was reported in the
      four partial-deficiency patients; no disease-wide frequency is inferred.
  sequelae:
  - target: Feeding difficulties
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Impaired oral mechanics can reduce safe and efficient feeding.
    evidence:
    - reference: PMID:22675738
      reference_title: LAMA2 Muscular Dystrophy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: As disease progresses, facial muscle weakness, temporomandibular joint contractures,
        and macroglossia may further impair feeding and can affect speech.
      explanation: GeneReviews explicitly identifies these contributors to progressive feeding
        impairment.
  - target: Oropharyngeal dysphagia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Facial weakness or tongue enlargement may worsen the oral phase of swallowing.
    evidence:
    - reference: PMID:32848593
      reference_title: 'LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers,
        and Clinical Trial Readiness.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Macroglossia and facial weakness might further contribute to the defective oral
        phase in LAMA2-RD patients.
      explanation: The review explicitly proposes contributors to the oral component of dysphagia;
        it does not establish every pharyngeal intermediate.
- name: Impaired mastication
  category: Gastrointestinal
  description: Chewing difficulty was reported in 53/90 Chinese congenital patients older than
    two years. The results text gives 58.9%; the table incorrectly prints 65.1%.
  phenotype_term:
    preferred_term: Impaired mastication
    term:
      id: HP:0005216
      label: Impaired mastication
  evidence:
  - reference: PMID:34281576
    reference_title: Natural history and genetic study of LAMA2-related muscular dystrophy in
      a large Chinese cohort.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In LAMA2-CMD patients over two years old, feeding problems such as chewing difficulty
      (58.9%, 53/90) and swallowing difficulty (12.2%, 11/90) were common.
    explanation: Uses the internally consistent results sentence instead of erroneous table
      percentages.
  sequelae:
  - target: Feeding difficulties
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Difficulty breaking down food prolongs or limits oral intake.
    evidence:
    - reference: PMID:31308722
      reference_title: Current understanding and treatment of cardiac and skeletal muscle pathology
        in laminin-α2 chain-deficient congenital muscular dystrophy.
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Feeding difficulties, swallowing abnormalities, and difficulty in chewing all
        contribute to poor weight gain in affected children.
      explanation: The clinical review explicitly attributes poor growth to feeding dysfunction.
- name: Oropharyngeal dysphagia
  category: Gastrointestinal
  description: A selected study of 14 severe nonambulant children found abnormal oral transfer
    in 13 and an abnormal pharyngeal phase in nine. In the Chinese congenital cohort swallowing
    difficulty was reported in 11/90 patients older than two years.
  phenotype_term:
    preferred_term: Oral-pharyngeal dysphagia
    term:
      id: HP:0200136
      label: Oral-pharyngeal dysphagia
  evidence:
  - reference: PMID:10332004
    reference_title: Feeding problems in merosin deficient congenital muscular dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Nine had an abnormal pharyngeal phase, with a delayed swallow reflex.
    explanation: Videofluoroscopy directly demonstrates pharyngeal swallowing impairment in
      the selected severe cohort.
  - reference: PMID:10332004
    reference_title: Feeding problems in merosin deficient congenital muscular dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The others all had an abnormal oral phase (breakdown and manipulation of food and
      transfer to oropharynx).
    explanation: Thirteen of fourteen severely affected children had an abnormal oral phase
      on videofluoroscopy; the preceding sentence identifies the youngest child as the only
      normal study.
  sequelae:
  - target: Aspiration
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Oropharyngeal swallowing dysfunction can cause this complication; individual
      occurrence is not inevitable.
    evidence:
    - reference: PMID:32848593
      reference_title: 'LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers,
        and Clinical Trial Readiness.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Swallowing difficulties can lead to aspiration, recurrent chest infections, and
        failure to thrive.
      explanation: Explicit clinical sequelae of dysphagia in the review.
  - target: Recurrent respiratory infections
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Oropharyngeal swallowing dysfunction can cause this complication; individual
      occurrence is not inevitable.
    evidence:
    - reference: PMID:32848593
      reference_title: 'LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers,
        and Clinical Trial Readiness.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Swallowing difficulties can lead to aspiration, recurrent chest infections, and
        failure to thrive.
      explanation: Explicit clinical sequelae of dysphagia in the review.
  - target: Failure to thrive
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Oropharyngeal swallowing dysfunction can cause this complication; individual
      occurrence is not inevitable.
    evidence:
    - reference: PMID:32848593
      reference_title: 'LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers,
        and Clinical Trial Readiness.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Swallowing difficulties can lead to aspiration, recurrent chest infections, and
        failure to thrive.
      explanation: Explicit clinical sequelae of dysphagia in the review.
- name: Aspiration
  category: Respiratory
  description: Frank aspiration was observed in three children during videofluoroscopy in the
    selected 14-child severe feeding series.
  phenotype_term:
    preferred_term: Aspiration
    term:
      id: HP:0002835
      label: Aspiration
  evidence:
  - reference: PMID:10332004
    reference_title: Feeding problems in merosin deficient congenital muscular dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Three of these also showed pooling of food in the larynx and three showed frank
      aspiration.
    explanation: Direct swallowing-study finding; the selected testing denominator is not a
      population frequency.
  sequelae:
  - target: Recurrent respiratory infections
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Aspiration provides one route to recurrent chest infection in addition to poor
      secretion clearance.
    evidence:
    - reference: PMID:32848593
      reference_title: 'LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers,
        and Clinical Trial Readiness.'
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Swallowing difficulties can lead to aspiration, recurrent chest infections, and
        failure to thrive.
      explanation: Explicit clinical sequelae of dysphagia in the review.
- name: Respiratory insufficiency due to muscle weakness
  category: Respiratory
  description: Intercostal and accessory respiratory muscle weakness can produce clinically
    significant ventilatory insufficiency. Diaphragm involvement is relatively limited functionally
    in assessed human cohorts.
  phenotype_term:
    preferred_term: Respiratory insufficiency due to muscle weakness
    term:
      id: HP:0002747
      label: Respiratory insufficiency due to muscle weakness
  evidence:
  - reference: PMID:32848593
    reference_title: 'LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers, and
      Clinical Trial Readiness.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Progressive, restrictive pulmonary insufficiency due to weakness of intercostal
      and accessory muscles is the most common cause of morbidity and mortality in LAMA2-RD.
    explanation: Clinical review explicitly attributes restrictive insufficiency to respiratory
      muscle weakness.
- name: Elbow flexion contracture
  category: Musculoskeletal
  description: Elbow flexion contractures progress in many severe patients; UK goniometry showed
    increasing restriction with age.
  phenotype_term:
    preferred_term: Elbow flexion contracture
    term:
      id: HP:0002987
      label: Elbow flexion contracture
  evidence:
  - reference: PMID:39213089
    reference_title: A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related
      Muscular Dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Descriptions of joint contractures based on the neurological examination (yes/no
      without further grading) were recorded in the CRF and were available for 18 patients and
      most frequently observed in the elbow (N = 10), hip (N = 9), long finger flexors (N =
      12), knee (N = 13) and ankle (N = 13) (Fig. 1).
    explanation: >-
      Elbow contractures were recorded in 10/18 Swiss participants: 14 never walked and four
      had attained walking. This mixed, age-variable LAMA2 cohort is not a congenital-only
      frequency estimate. The Swiss observation does not specify flexion direction;
      UK goniometry below supplies that specificity.
  - reference: PMID:32910545
    reference_title: 'LAMA2-related muscular dystrophy: Natural history of a large pediatric
      cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We observed a linear increase in elbow flexor contractures in CD subjects.
    explanation: UK longitudinal data directly establish flexion specificity and progression.
- name: Knee flexion contracture
  category: Musculoskeletal
  description: Knee flexion contractures were measured longitudinally in the UK cohort and recorded
    in 13/18 Swiss participants.
  phenotype_term:
    preferred_term: Knee flexion contracture
    term:
      id: HP:0006380
      label: Knee flexion contracture
  evidence:
  - reference: PMID:39213089
    reference_title: A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related
      Muscular Dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Descriptions of joint contractures based on the neurological examination (yes/no
      without further grading) were recorded in the CRF and were available for 18 patients and
      most frequently observed in the elbow (N = 10), hip (N = 9), long finger flexors (N =
      12), knee (N = 13) and ankle (N = 13) (Fig. 1).
    explanation: >-
      Knee contractures were recorded in 13/18 Swiss participants: 14 never walked and four
      had attained walking. This mixed, age-variable LAMA2 cohort is not a congenital-only
      frequency estimate. The Swiss observation does not specify flexion direction;
      UK goniometry below supplies that specificity.
  - reference: PMID:32910545
    reference_title: 'LAMA2-related muscular dystrophy: Natural history of a large pediatric
      cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'The following longitudinally collected variables were considered: weight, current
      motor ability, goniometry measurements of right hip flexion, knee flexion and elbow flexion,
      scoliosis (defined as Cobb Angle >20°), respiratory complications, spirometry measurements
      (Forced Vital Capacity percentage‐FVC%‐predicted and cough peak of flow –PEF‐ when available),
      swallowing and feeding abilities, cardiac function, epilepsy and antiepileptic treatment.'
    explanation: Methods identify the flexion directions measured; the Swiss clinical observation
      independently establishes contractures at these joints.
- name: Hip flexion contracture
  category: Musculoskeletal
  description: Hip flexion contractures were assessed by UK goniometry; hip contractures affected
    nine of 18 Swiss participants.
  phenotype_term:
    preferred_term: Hip flexion contracture
    term:
      id: HP:0020025
      label: Hip flexion contracture
  evidence:
  - reference: PMID:39213089
    reference_title: A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related
      Muscular Dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Descriptions of joint contractures based on the neurological examination (yes/no
      without further grading) were recorded in the CRF and were available for 18 patients and
      most frequently observed in the elbow (N = 10), hip (N = 9), long finger flexors (N =
      12), knee (N = 13) and ankle (N = 13) (Fig. 1).
    explanation: >-
      Hip contractures were recorded in 9/18 Swiss participants: 14 never walked and four had
      attained walking. This mixed, age-variable LAMA2 cohort is not a congenital-only
      frequency estimate. The Swiss observation does not specify flexion direction; UK
      goniometry below supplies that specificity.
  - reference: PMID:32910545
    reference_title: 'LAMA2-related muscular dystrophy: Natural history of a large pediatric
      cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'The following longitudinally collected variables were considered: weight, current
      motor ability, goniometry measurements of right hip flexion, knee flexion and elbow flexion,
      scoliosis (defined as Cobb Angle >20°), respiratory complications, spirometry measurements
      (Forced Vital Capacity percentage‐FVC%‐predicted and cough peak of flow –PEF‐ when available),
      swallowing and feeding abilities, cardiac function, epilepsy and antiepileptic treatment.'
    explanation: Methods identify the flexion directions measured; the Swiss clinical observation
      independently establishes contractures at these joints.
- name: Ankle contracture
  category: Musculoskeletal
  description: Ankle contractures were present in 13/18 Swiss participants, a mixed congenital
    and ambulant LAMA2 cohort.
  phenotype_term:
    preferred_term: Ankle contracture
    term:
      id: HP:0034677
      label: Ankle contracture
  evidence:
  - reference: PMID:39213089
    reference_title: A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related
      Muscular Dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Descriptions of joint contractures based on the neurological examination (yes/no
      without further grading) were recorded in the CRF and were available for 18 patients and
      most frequently observed in the elbow (N = 10), hip (N = 9), long finger flexors (N =
      12), knee (N = 13) and ankle (N = 13) (Fig. 1).
    explanation: >-
      Ankle contractures were recorded in 13/18 Swiss participants: 14 never walked and four
      had attained walking. This mixed, age-variable LAMA2 cohort is not a congenital-only
      frequency estimate. The source does not specify a fixed ankle position or
      grade contracture severity.
- name: Finger flexion contracture
  category: Musculoskeletal
  description: Long finger flexor contractures were reported in 30/42 complete-deficiency and
    2/4 partial-deficiency UK patients.
  phenotype_term:
    preferred_term: Flexion contracture of finger
    term:
      id: HP:0012785
      label: Flexion contracture of finger
  evidence:
  - reference: PMID:32910545
    reference_title: 'LAMA2-related muscular dystrophy: Natural history of a large pediatric
      cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Long finger flexor contractures were reported in 30/42 (71%) CD patients as well
      as 2/4 PD patients.
    explanation: Direct anatomical and subgroup-specific observation.
- name: Neck rigidity
  category: Musculoskeletal
  description: Neck rigidity was recorded in 20/42 complete-deficiency and 1/4 partial-deficiency
    UK patients.
  phenotype_term:
    preferred_term: Stiff neck
    term:
      id: HP:0025258
      label: Stiff neck
  evidence:
  - reference: PMID:32910545
    reference_title: 'LAMA2-related muscular dystrophy: Natural history of a large pediatric
      cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Neck rigidity was reported in 21 patients (20 CD and one PD), spine rigidity in
      15 (13 CD and two PD), and lordosis in 12 (10 CD and two PD).
    explanation: The UK cohort separates neck, spine and lordosis findings and complete from
      partial deficiency.
- name: Hyperlordosis
  category: Musculoskeletal
  description: Lordosis was recorded in 10 complete-deficiency and two partial-deficiency UK
    patients. Cervical, thoracic and lumbar involvement can have different mechanical consequences.
  phenotype_term:
    preferred_term: Hyperlordosis
    term:
      id: HP:0003307
      label: Hyperlordosis
  evidence:
  - reference: PMID:32910545
    reference_title: 'LAMA2-related muscular dystrophy: Natural history of a large pediatric
      cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Neck rigidity was reported in 21 patients (20 CD and one PD), spine rigidity in
      15 (13 CD and two PD), and lordosis in 12 (10 CD and two PD).
    explanation: The UK cohort separates neck, spine and lordosis findings and complete from
      partial deficiency.
  sequelae:
  - target: Oropharyngeal dysphagia
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Severe cervical lordosis can impair swallowing; the relation is limited to
      the cervical component of this broader phenotype.
    evidence:
    - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK97333/
      reference_title: LAMA2 Muscular Dystrophy - GeneReviews® - NCBI Bookshelf
      supports: SUPPORT
      evidence_source: OTHER
      snippet: This weakness may progress to a severe cervical lordosis in late adolescence,
        affecting the capacity to swallow and increasing the risk of food aspiration.
      explanation: The preceding chapter sentence identifies neck flexor weakness; the consequence
        is specifically cervical lordosis.
  - target: Scoliosis
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Thoracic and lumbar lordosis can aggravate scoliosis, as described in the full
      GeneReviews clinical chapter; this does not identify the cause of every scoliotic curve.
    evidence:
    - reference: url:https://www.ncbi.nlm.nih.gov/books/NBK97333/
      reference_title: LAMA2 Muscular Dystrophy - GeneReviews® - NCBI Bookshelf
      supports: SUPPORT
      evidence_source: OTHER
      snippet: is aggravated by thoracic and lumbar lordosis and frequently observed from the
        first decade of life
      explanation: The explicit subject immediately preceding this clause in the chapter is
        Scoliosis; this is a qualified aggravating relation.
- name: Hip dislocation
  category: Musculoskeletal
  description: Reported in the UK congenital/partial-deficiency cohort; counts and subgroup
    scope are given in the evidence.
  phenotype_term:
    preferred_term: Hip dislocation
    term:
      id: HP:0002827
      label: Hip dislocation
  evidence:
  - reference: PMID:32910545
    reference_title: 'LAMA2-related muscular dystrophy: Natural history of a large pediatric
      cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Hip dislocation was reported in 12 CD and two PD patients, pectus excavatum in
      two CD and pectus carinatum in two CD patient.
    explanation: Directly records these structural findings in the UK cohort without establishing
      their individual mechanisms.
- name: Pectus excavatum
  category: Musculoskeletal
  description: Reported in the UK congenital/partial-deficiency cohort; counts and subgroup
    scope are given in the evidence.
  phenotype_term:
    preferred_term: Pectus excavatum
    term:
      id: HP:0000767
      label: Pectus excavatum
  evidence:
  - reference: PMID:32910545
    reference_title: 'LAMA2-related muscular dystrophy: Natural history of a large pediatric
      cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Hip dislocation was reported in 12 CD and two PD patients, pectus excavatum in
      two CD and pectus carinatum in two CD patient.
    explanation: Directly records these structural findings in the UK cohort without establishing
      their individual mechanisms.
- name: Pectus carinatum
  category: Musculoskeletal
  description: Reported in the UK congenital/partial-deficiency cohort; counts and subgroup
    scope are given in the evidence.
  phenotype_term:
    preferred_term: Pectus carinatum
    term:
      id: HP:0000768
      label: Pectus carinatum
  evidence:
  - reference: PMID:32910545
    reference_title: 'LAMA2-related muscular dystrophy: Natural history of a large pediatric
      cohort.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Hip dislocation was reported in 12 CD and two PD patients, pectus excavatum in
      two CD and pectus carinatum in two CD patient.
    explanation: Directly records these structural findings in the UK cohort without establishing
      their individual mechanisms.
- name: Weak cry
  category: Neuromuscular
  description: Weak cry was an initial symptom in 48/116 Chinese clinical LAMA2-CMD patients;
    the onset-symptom count is not limited to the neonatal period.
  phenotype_term:
    preferred_term: Weak cry
    term:
      id: HP:0001612
      label: Weak cry
  evidence:
  - reference: PMID:34281576
    reference_title: Natural history and genetic study of LAMA2-related muscular dystrophy in
      a large Chinese cohort.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The onset symptoms in LAMA2-CMD were variable combinations of severe muscle weakness
      (n = 114), hypotonia (n = 114), weak cry (n = 48), neonatal feeding difficulty (n = 30),
      neonatal respiratory difficulty (n = 9).
    explanation: Direct congenital-cohort presenting symptom.
- name: Reduced bone mineral density
  category: Musculoskeletal
  description: Femoral bone density was reduced in all assessed adults and seven of ten children
    in the Dutch mixed life-span cohort. Lumbar abnormalities were less frequent.
  phenotype_term:
    preferred_term: Reduced bone mineral density
    term:
      id: HP:0004349
      label: Reduced bone mineral density
  evidence:
  - reference: PMID:37476021
    reference_title: 'LAMA2-Related Muscular Dystrophy Across the Life Span: A Cross-sectional
      Study.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'The femoral mineral bone density was reduced in all adults (t score: −2.6 ± 1.4)
      and in 7 of 10 pediatric patients (z score: −3.5 ± 1.8).'
    explanation: Direct densitometry in the broader LAMA2 spectrum, not a severe congenital-only
      estimate.
  sequelae:
  - target: Pathologic fractures
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: Reduced bone quality predisposes to fragility fracture; individual contributors
      to the bone deficit remain unresolved.
    evidence:
    - reference: PMID:37476021
      reference_title: 'LAMA2-Related Muscular Dystrophy Across the Life Span: A Cross-sectional
        Study.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Decreased bone quality leading to fragility fractures was seen in most of the
        patients.
      explanation: The authors explicitly relate reduced bone quality to fragility; the actual
        fracture count is 11/27.
- name: Pontine hypoplasia
  category: Neurologic
  description: Ten of twelve re-reviewed Swiss MRIs showed pontine hypoplasia. This selected
    imaging denominator includes the broader LAMA2 spectrum.
  phenotype_term:
    preferred_term: Hypoplasia of the pons
    term:
      id: HP:0012110
      label: Hypoplasia of the pons
  evidence:
  - reference: PMID:39213089
    reference_title: A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related
      Muscular Dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In ten of the 12 reevaluated MRIs we found pontine hypoplasia, as well as four
      with a large interthalamic adhesion.
    explanation: Direct MRI observation; a specific developmental causal pathway was not established.
- name: Enlarged cisterna magna
  category: Neurologic
  description: Five of twelve re-reviewed Swiss scans showed an enlarged cisterna magna; these
    structural findings were not considered epileptogenic by the authors.
  phenotype_term:
    preferred_term: Enlarged cisterna magna
    term:
      id: HP:0002280
      label: Enlarged cisterna magna
  evidence:
  - reference: PMID:39213089
    reference_title: A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related
      Muscular Dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'Furthermore, nine of the 12 reevaluated patients had structural abnormalities
      of the brainstem-vermis angle: four patients had a Blake’s pouch cyst, one of whom needed
      a ventriculo-peritoneal shunt; and five patients had a megacisterna magna (brainstem-vermis-angle
      10–18°)[44].'
    explanation: The results distinguish four Blake pouch cysts from five enlarged cisterna
      magna findings in a selected imaging subset.
- name: Blake pouch cyst
  category: Neurologic
  description: Four of twelve re-reviewed Swiss scans showed a Blake pouch cyst in the results
    section; the discussion gives an inconsistent three. One patient required shunting.
  phenotype_term:
    preferred_term: Blake's pouch cyst
    term:
      id: HP:0033140
      label: Blake's pouch cyst
  evidence:
  - reference: PMID:39213089
    reference_title: A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related
      Muscular Dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'Furthermore, nine of the 12 reevaluated patients had structural abnormalities
      of the brainstem-vermis angle: four patients had a Blake’s pouch cyst, one of whom needed
      a ventriculo-peritoneal shunt; and five patients had a megacisterna magna (brainstem-vermis-angle
      10–18°)[44].'
    explanation: The results distinguish four Blake pouch cysts from five enlarged cisterna
      magna findings in a selected imaging subset.
  sequelae:
  - target: Hydrocephalus
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: The reported Blake pouch cyst was complicated by hydrocephalus in one patient;
      this does not imply every cyst causes hydrocephalus.
    evidence:
    - reference: PMID:39213089
      reference_title: A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related
        Muscular Dystrophy.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Although, to our knowledge, not previously reported, we observed the frequent
        occurrence of a large tegmento-vermian angle (9/12) classified as megacisterna magna
        or Blake’s pouch cyst (3/12), causing a hydrocephalus and requiring a ventriculoperitoneal
        shunt in one patient.
      explanation: The discussion explicitly attributes hydrocephalus to the posterior-fossa
        cyst abnormality; its aggregate cyst count differs from the results.
- name: Hydrocephalus
  category: Neurologic
  description: Hydrocephalus requiring shunting was reported in one Swiss patient with a Blake
    pouch cyst; this is a case-specific complication.
  phenotype_term:
    preferred_term: Hydrocephalus
    term:
      id: HP:0000238
      label: Hydrocephalus
  evidence:
  - reference: PMID:39213089
    reference_title: A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related
      Muscular Dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Although, to our knowledge, not previously reported, we observed the frequent occurrence
      of a large tegmento-vermian angle (9/12) classified as megacisterna magna or Blake’s pouch
      cyst (3/12), causing a hydrocephalus and requiring a ventriculoperitoneal shunt in one
      patient.
    explanation: The discussion explicitly attributes hydrocephalus to the posterior-fossa cyst
      abnormality; its aggregate cyst count differs from the results.
- name: Motor regression
  category: Neuromuscular
  description: Motor regression occurred in 34/109 Chinese clinical congenital patients and
    often coincided with progressive contractures at six to nine years. Young children can also
    gain skills, so progression is not uniformly monotonic.
  phenotype_term:
    preferred_term: Motor regression
    term:
      id: HP:0033044
      label: Motor regression
  evidence:
  - reference: PMID:34281576
    reference_title: Natural history and genetic study of LAMA2-related muscular dystrophy in
      a large Chinese cohort.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Motor regression in LAMA2-CMD mainly occurred concurrently with rapid progression
      of contractures during 6-9 years old.
    explanation: The clinical temporal association does not by itself prove that contractures
      account for every lost skill.
genetic:
- name: LAMA2
  gene_term:
    preferred_term: LAMA2
    term:
      id: hgnc:6482
      label: LAMA2
  relationship_type: CAUSATIVE
  notes: >-
    LAMA2 at 6q22-q23 encodes the laminin alpha-2 chain. Biallelic loss of function is the sole
    established cause of this disease. Over 300 pathogenic variants are reported, and the allele
    class is prognostically meaningful: nonsense, frameshift and whole-exon deletion alleles
    dominate the congenital severe form, whereas missense and leaky splice alleles that leave
    residual protein cluster at the limb-girdle end. Variants affecting the C-terminal LG domains
    are additionally associated with brain malformation, which is mechanistically coherent
    because the LG module is the receptor-binding end of the molecule in both muscle and brain.
  evidence:
  - reference: PMID:7550355
    reference_title: "Mutations in the laminin alpha 2-chain gene (LAMA2) cause merosin-deficient congenital muscular dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We therefore investigated LAMA2 for the presence of disease-causing mutations in laminin alpha 2 chain-deficient CMD families and now report splice site and nonsense mutations in two families leading presumably to a truncated laminin alpha 2 protein."
    explanation: The report that established LAMA2 as the causal gene.
  - reference: PMID:34281576
    reference_title: "Natural history and genetic study of LAMA2-related muscular dystrophy in a large Chinese cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The top three high-frequency disease-causing variants in Han Chinese patients were c.7147C > T (p.R2383*), exon 4 deletion, and c.5156_5159del (p.K1719Rfs*5)."
    explanation: >-
      Records the recurrent Han Chinese alleles. Population-specific recurrence matters
      for testing strategy - a targeted assay is only worth building where an allele
      actually recurs.
  - reference: PMID:34281576
    reference_title: "Natural history and genetic study of LAMA2-related muscular dystrophy in a large Chinese cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Copy number variations were identified in 26.4% of survivors and 50.0% of nonsurvivors, suggesting that copy number variations were associated with lower rate of survival (p = 0.029)."
    explanation: >-
      The one prognostic genetic association in this disease rather than a merely
      descriptive one: copy-number variants are over-represented among non-survivors.
      Quoted with the authors' own hedge ("suggesting") intact - it is a single-cohort
      association at p = 0.029, not an established rule.
  - reference: PMID:37182895
    reference_title: "Brain MRI Abnormalities, Epilepsy and Intellectual Disability in LAMA2 Related Dystrophy - a Genotype/Phenotype Correlation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A new brazilian possible founder variant was found in 11 patients (21,15%) (c.1255del; p. Ile419Leufs*4)."
    explanation: >-
      A second population-specific recurrent allele, in a different cohort, quoted with
      the authors' own "possible founder" hedge rather than asserted as established.
  - reference: PMID:32457577
    reference_title: "A Family of Laminin α2 Chain-Deficient Mouse Mutants: Advancing the Research on LAMA2-CMD."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "which result in a large clinical heterogeneity of the disease"
    explanation: Supports the link between the size of the LAMA2 allelic spectrum and the clinical heterogeneity described here.
  - reference: PMID:37182895
    reference_title: "Brain MRI Abnormalities, Epilepsy and Intellectual Disability in LAMA2 Related Dystrophy - a Genotype/Phenotype Correlation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "There was a relation between gene variants affecting the laminin-α2 LG-domain and the presence of brain malformation (P = 0.016)."
    explanation: Establishes the LG-domain genotype correlation with cortical malformation recorded in these notes.
  case_fractions:
  - population: Han Chinese LAMA2-related muscular dystrophy cohort
    case_fraction_percent: 56.9
    cohort_size: 116
    notes: >-
      Share of congenital-form patients carrying a nonsense variant, contrasted with 21.4% in the
      limb-girdle subtype. Recorded as an allele-class share within the gene, not as a share of
      cases attributable to the gene, which is 100% by definition for a monogenic disease.
    evidence:
    - reference: PMID:34281576
      reference_title: "Natural history and genetic study of LAMA2-related muscular dystrophy in a large Chinese cohort."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Nonsense variants were more frequent in LAMA2-CMD (56.9%, 66/116) than in LGMDR23 (21.4%, 3/14), while missense disease-causing variants were more frequent in LGMDR23 (71.4%, 10/14) than in LAMA2-CMD (12.9%, 15/116)."
      explanation: Gives the nonsense-allele share in the congenital-form group recorded here.
diagnosis:
- name: LAMA2 molecular genetic testing
  presence: PRESENT
  description: >-
    Identification of biallelic pathogenic LAMA2 variants establishes the diagnosis.
    Next-generation sequencing has largely displaced the biopsy-first pathway, but copy-number
    analysis matters: single and multi-exon deletions account for a substantial minority of
    alleles and are missed by sequencing alone. Functional splice assessment can clarify
    suspected splice-altering variants: the Swiss cohort confirmed aberrant splicing for
    c.4960-17C>A. This variant-level evidence does not establish a universal RNA-sequencing
    workflow, preferred tissue, or diagnostic yield after single-allele detection.
  evidence:
  - reference: PMID:22675738
    reference_title: "LAMA2 Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The diagnosis of LAMA2 muscular dystrophy is established in a proband with suggestive findings and biallelic (homozygous or compound heterozygous) pathogenic variants in LAMA2 identified by molecular genetic testing."
    explanation: States the molecular diagnostic criterion.
  - reference: PMID:32848593
    reference_title: "LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers, and Clinical Trial Readiness."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Next-generation sequencing (NGS) has greatly improved diagnostic abilities for LAMA2-RD, and the majority of patients with merosin deficiency carry recessive pathogenic variants in the LAMA2 gene."
    explanation: Supports the primacy of sequencing in the current diagnostic pathway.
  - reference: PMID:39213089
    reference_title: A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related Muscular
      Dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We confirmed aberrant splicing for the c.4960-17C > A variant (see Figure S1 and Table
      S1).
    explanation: The Swiss clinical study reports functional confirmation for a specific intronic
      variant. It supports an adjunctive splice assessment, not the broader report-proposed RNA sequencing
      or RT-PCR algorithm for every unresolved patient.
- name: Muscle biopsy merosin immunostaining
  presence: PRESENT
  description: >-
    Absent or reduced laminin alpha-2 immunostaining on muscle, on a dystrophic background. It
    remains useful for grading complete versus partial deficiency, but the residual-protein
    reading is not reliable enough to predict phenotype in an individual patient, and skin biopsy
    can substitute where complete deficiency is suspected.
  evidence:
  - reference: PMID:39213089
    reference_title: "A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "However, the amount of merosin in muscle biopsy does not enable a clear prediction of clinical phenotype"
    explanation: States the prognostic limitation of the immunostain that this entry records.
  - reference: PMID:32848593
    reference_title: "LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers, and Clinical Trial Readiness."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Absence of laminin alpha 2 at the epidermal and adnexal basement membranes and intradermal sensory nerves can be demonstrated in skin biopsies, particularly in cases of complete laminin alpha 2 deficiency"
    explanation: Supports skin biopsy as an alternative demonstration of the protein deficiency.
- name: Brain MRI white matter signal
  presence: PRESENT
  description: >-
    Diffuse periventricular and subcortical T2 hyperintensity is close to universal beyond six
    months and is often the finding that redirects an undiagnosed floppy infant towards LAMA2.
    Below six months it may be absent, so a normal early MRI does not exclude the diagnosis.
    Re-reading the MRI specifically for cortical malformation is worthwhile: it is frequently
    missed on the initial report.
  evidence:
  - reference: PMID:32848593
    reference_title: "LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers, and Clinical Trial Readiness."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Characteristic brain white matter (WM) hypointensity on T1 magnetic resonance imaging (MRI), and increased T2 signal in the periventricular and subcortical WM, are invariably observed in most patients older than 6 months"
    explanation: Establishes the MRI finding and its age threshold.
  - reference: PMID:37182895
    reference_title: "Brain MRI Abnormalities, Epilepsy and Intellectual Disability in LAMA2 Related Dystrophy - a Genotype/Phenotype Correlation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "shows the importance of reviewing the brain MRI of patients with LAMA2-RD"
    explanation: Supports the recommendation to re-review the MRI for cortical malformation.
- name: Motor nerve conduction study
  presence: PRESENT
  description: >-
    Slowed motor conduction supports merosin deficiency over other congenital muscular
    dystrophies. It is supportive rather than decisive: some cohorts report normal studies, and
    it is not needed once genetic testing is available.
  evidence:
  - reference: PMID:8576559
    reference_title: "Demyelinating peripheral neuropathy in merosin-deficient congenital muscular dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All but two of the 10 merosin-deficient cases had reduced motor nerve conduction, whereas all the merosin-positive cases had normal results."
    explanation: Establishes the discriminating value of the study between merosin-deficient and merosin-positive congenital muscular dystrophy.
  - reference: PMID:39213089
    reference_title: "A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Electrophysiological nerve conduction studies were done in three patients (two with motor and sensory measurements, one patient with only sensory measurement) and were reported as being normal."
    explanation: Records a cohort in which the studies were normal, which is why this test is described as supportive rather than decisive.
progression:
- phase: Neonatal and infantile
  notes: >-
    Onset is at or within days of birth in three quarters of congenital-form patients: profound
    hypotonia, weak cry, poor spontaneous movement, sometimes neonatal feeding or respiratory
    difficulty. The mouse data suggest the pathology is already well established by this point,
    with apoptotic fibres from postnatal day 1 and full dystrophic architecture by day 4, which
    is the argument for intervening as early as diagnosis permits.
  evidence:
  - reference: PMID:34281576
    reference_title: "Natural history and genetic study of LAMA2-related muscular dystrophy in a large Chinese cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The onset symptoms in LAMA2-CMD were variable combinations of severe muscle weakness (n = 114), hypotonia (n = 114), weak cry (n = 48), neonatal feeding difficulty (n = 30), neonatal respiratory difficulty (n = 9)."
    explanation: Enumerates the presenting features of this phase in a 116-patient congenital-form cohort.
  - reference: PMID:31586140
    reference_title: "Early skeletal muscle pathology and disease progress in the dy(3K)/dy(3K) mouse model of congenital muscular dystrophy with laminin α2 chain-deficiency."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Therapeutic tests in the dy3K/dy3K mouse model should therefore be initiated shortly after birth, but should also take into account timing and correlation between regenerative and pathogenic events."
    explanation: The authors' own inference about intervention timing from the perinatal onset of pathology.
- phase: Early and middle childhood
  notes: >-
    Motor milestones are attained late and incompletely: head control by about six months and
    independent sitting by about eleven months in most, but ambulation in fewer than a fifth.
    Contractures accumulate steadily and scoliosis appears in the non-ambulant, typically after
    six years. Motor regression, when it happens, clusters in the six-to-nine-year window and
    tracks the contracture phase rather than a separate loss of strength.
  evidence:
  - reference: PMID:34281576
    reference_title: "Natural history and genetic study of LAMA2-related muscular dystrophy in a large Chinese cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Motor regression in LAMA2-CMD mainly occurred concurrently with rapid progression of contractures during 6-9 years old."
    explanation: Times the regression window and links it to contracture progression.
  - reference: PMID:32848593
    reference_title: "LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers, and Clinical Trial Readiness."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Progressive scoliosis is common after 6 years of age, leading to a surgical correction in most patients."
    explanation: Times the onset of scoliosis and its surgical burden to this phase.
- phase: Adolescence and respiratory decline
  notes: >-
    The dominant events of the second decade are respiratory and nutritional. Forced vital
    capacity falls at about 2.9% predicted per year, nocturnal non-invasive ventilation is started
    at a median of around twelve years, and gastrostomy at around eleven. Spinal surgery is
    common. Cardiac abnormalities, mostly subclinical, are increasingly detected.
  evidence:
  - reference: PMID:32910545
    reference_title: "LAMA2-related muscular dystrophy: Natural history of a large pediatric cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Twenty-two CD required nocturnal noninvasive ventilation (median age 11.7 years)."
    explanation: Dates the ventilatory transition that defines this phase.
  - reference: PMID:32910545
    reference_title: "LAMA2-related muscular dystrophy: Natural history of a large pediatric cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Nineteen CD and one PD patient required gastrostomy insertion for failure to thrive and/or unsafe swallow (median age 10.9 years)."
    explanation: Dates the nutritional transition in the same cohort.
- phase: Survival and cause of death
  notes: >-
    Mortality is driven by respiratory infection rather than by cardiac or neurological disease.
    About 30% of early-onset patients die within the first decade in one review's summary; in a
    tertiary cohort seven of 42 complete-deficiency patients died at a median of 12 years, and in
    a 130-patient national cohort 24 died, mostly of severe pneumonia. Survival into adulthood is
    routine in the partial-deficiency subtype.
  evidence:
  - reference: PMID:31308722
    reference_title: "Current understanding and treatment of cardiac and skeletal muscle pathology in laminin-α2 chain-deficient congenital muscular dystrophy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The most common cause of death in early-onset LAMA2 MD is respiratory tract infection, with 30% of them dying within the first decade of life."
    explanation: Gives both the leading cause of death and a first-decade mortality figure.
  - reference: PMID:32910545
    reference_title: "LAMA2-related muscular dystrophy: Natural history of a large pediatric cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Seven CD patients died at median age 12 years."
    explanation: Gives median age at death in a well-characterised complete-deficiency cohort.
treatments:
- name: Multidisciplinary Supportive Care
  description: >-
    There is no disease-modifying therapy, so management is anticipatory surveillance plus
    intervention at defined thresholds, delivered by a coordinated team. The surveillance list is
    long because the complications are: nutrition and swallow safety, neurologic status,
    pulmonary function, cognition and education, mobility, cardiac rhythm and function, vision,
    and bone quality. The life-span cohort authors recommend ECG, Holter monitoring and
    echocardiography, recurrent bone mineral density assessment, and vitamin D/calcium
    supplementation. These are surveillance and supportive-care recommendations, not measured
    disease-modifying treatment effects.
  treatment_term:
    preferred_term: multidisciplinary supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  therapeutic_modality: BEHAVIORAL
  evidence:
  - reference: PMID:22675738
    reference_title: "LAMA2 Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "It is recommended that multidisciplinary care be provided by specialists in neurology, gastroenterology, nutrition, orthopedics, occupational and physical therapy, speech and language therapy, education, psychiatry, pulmonary medicine, cardiology, ophthalmology, and social work."
    explanation: GeneReviews states the multidisciplinary management recommendation this treatment records.
  - reference: PMID:37476021
    reference_title: 'LAMA2-Related Muscular Dystrophy Across the Life Span: A Cross-sectional Study.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: We advise cardiac surveillance by regular screening of patients with ECG, Holter monitor,
      and echocardiography with advanced techniques for early detection and treatment of cardiac manifestations.
    explanation: The authors recommend cardiac screening after their mixed-age LAMA2 cohort assessment.
      This is clinical guidance, not a trial demonstrating surveillance efficacy.
  - reference: PMID:37476021
    reference_title: 'LAMA2-Related Muscular Dystrophy Across the Life Span: A Cross-sectional Study.'
    supports: SUPPORT
    evidence_source: OTHER
    snippet: Based on the low bone quality, we further recommend recurrent bone mineral density assessment
      and optimization of bone quality through vitamin D and calcium suppletion.
    explanation: The recommendation follows cohort densitometry and fragility-fracture findings. The
      study did not test supplementation as a disease-modifying treatment or determine a congenital-only
      screening interval.

- name: Non-Invasive Ventilation
  description: >-
    Nocturnal non-invasive ventilation for restrictive respiratory failure, started at a median
    of around twelve years in the complete-deficiency form. Long-term invasive ventilation or
    tracheostomy is uncommon in paediatric practice; invasive support is generally reserved for
    short periods during intercurrent infection.
  treatment_term:
    preferred_term: nocturnal non-invasive ventilation
    term:
      id: NCIT:C171457
      label: Non-Invasive Mechanical Ventilation
  therapeutic_modality: DEVICE
  target_mechanisms:
  - target: Respiratory Muscle Weakness and Reduced Chest Wall Compliance
    treatment_effect: BYPASSES
    description: >-
      Ventilatory support substitutes for the failing respiratory pump rather than acting on the
      muscle lesion, and it does not slow the decline in vital capacity.
  evidence:
  - reference: PMID:32910545
    reference_title: "LAMA2-related muscular dystrophy: Natural history of a large pediatric cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Twenty-two CD required nocturnal noninvasive ventilation (median age 11.7 years)."
    explanation: Documents the use and timing of nocturnal non-invasive ventilation in this population.
  - reference: PMID:32848593
    reference_title: "LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers, and Clinical Trial Readiness."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "While invasive ventilation might become necessary for short periods and typically during times of respiratory infections, long-term use of invasive ventilation or use of ventilation via a tracheostomy is rare in pediatric LAMA2-RD patients."
    explanation: Supports the preference for non-invasive over invasive long-term support.
- name: Gastrostomy Feeding
  description: Gastrostomy supports nutrition when oral intake is inadequate or swallowing is
    unsafe. Nineteen complete-deficiency and one partial-deficiency UK patients received a tube;
    the observed median age was five years, versus a 10.9-year time-to-event estimate. A selected
    feeding series reported improved weight gain and fewer chest infections after placement.
    Tube feeding does not guarantee normal growth or eliminate all aspiration risk.
  treatment_term:
    preferred_term: gastrostomy tube placement
    term:
      id: NCIT:C157864
      label: Gastrostomy Tube Procedure
  therapeutic_modality: SURGERY
  evidence:
  - reference: PMID:32910545
    reference_title: "LAMA2-related muscular dystrophy: Natural history of a large pediatric cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Nineteen CD and one PD patient required gastrostomy insertion for failure to thrive and/or unsafe swallow (median age 10.9 years)."
    explanation: The quoted 10.9 years is a time-to-event estimate; the observed median gastrostomy
      age was five years. Gastrostomy requirement does not measure all feeding impairment.
  - reference: PMID:10332004
    reference_title: Feeding problems in merosin deficient congenital muscular dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: As a result of the study five children had a gastrostomy, which stopped the chest
      infections and improved weight gain.
    explanation: Within-series improvement supports feeding-related morbidity; it is not a controlled
      treatment effect.
- name: Physical Therapy and Contracture Management
  description: >-
    Stretching, splinting, orthoses and positioning to slow contracture and preserve what function
    exists. Given that contracture is driven by early fibrogenesis and accumulates linearly, this
    is a rate-limiting intervention rather than a preventive one.
  treatment_term:
    preferred_term: physical therapy
    term:
      id: NCIT:C15302
      label: Physical Therapy
  therapeutic_modality: BEHAVIORAL
  target_mechanisms:
  - target: Endomysial Fibrosis and Replacement of Muscle
    treatment_effect: MODULATES
    description: >-
      Mechanical stretching opposes the shortening produced by fibrotic replacement without
      addressing the matrix deposition itself.
  evidence:
  - reference: PMID:22675738
    reference_title: "LAMA2 Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "It is recommended that multidisciplinary care be provided by specialists in neurology, gastroenterology, nutrition, orthopedics, occupational and physical therapy, speech and language therapy, education, psychiatry, pulmonary medicine, cardiology, ophthalmology, and social work."
    explanation: GeneReviews includes physical and occupational therapy in the recommended management team.
- name: Scoliosis Surgery
  description: >-
    Posterior spinal instrumentation and fusion for progressive scoliosis, needed by a
    substantial minority of non-ambulant patients: nine of 33 with scoliosis in one cohort and
    five of ten in another. It is a seating and comfort intervention as much as a respiratory one.
  treatment_term:
    preferred_term: spinal fusion for neuromuscular scoliosis
    term:
      id: NCIT:C157986
      label: Spinal Fusion
  therapeutic_modality: SURGERY
  evidence:
  - reference: PMID:32910545
    reference_title: "LAMA2-related muscular dystrophy: Natural history of a large pediatric cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Thirty-two CD and one PD patient developed scoliosis, nine underwent spinal surgery."
    explanation: Gives the proportion of scoliotic patients proceeding to surgery.
  - reference: PMID:39213089
    reference_title: "A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In our cohort five out of ten patients with CMD needed a surgical intervention for their severe scoliosis."
    explanation: Independent cohort corroboration of the surgical rate.
- name: Antiepileptic Drug Therapy
  description: >-
    Seizures in this disease are usually controlled with first-line antiepileptic drugs where
    there is no underlying cortical anomaly. Where a cortical malformation is present, drug
    resistance is reported, so the imaging finding has direct therapeutic implications.
  treatment_term:
    preferred_term: antiepileptic drug therapy
    term:
      id: NCIT:C64172
      label: Anticonvulsant Therapy
    therapeutic_agent:
    - preferred_term: anticonvulsant agent
      term:
        id: NCIT:C264
        label: Anticonvulsant Agent
  therapeutic_modality: SMALL_MOLECULE
  evidence:
  - reference: PMID:32848593
    reference_title: "LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers, and Clinical Trial Readiness."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Epilepsy should be monitored for and usually can be controlled with first-line antiepileptic drugs."
    explanation: States the recommendation and the expected response.
  - reference: PMID:39213089
    reference_title: "A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "One had continuous spike-waves during sleep (CSWS) and one had drug-resistant frequent focal seizures with impaired awareness (cortical malformation in one patient)."
    explanation: Documents the drug-resistant subgroup associated with cortical malformation.
- name: Genetic Counseling
  description: >-
    Autosomal recessive counselling with a 25% recurrence risk per pregnancy. Once the familial
    variants are known, carrier testing, prenatal and preimplantation genetic testing become
    available, which matters in a disease with no treatment and a severe natural history.
  treatment_term:
    preferred_term: genetic counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  therapeutic_modality: BEHAVIORAL
  evidence:
  - reference: PMID:22675738
    reference_title: "LAMA2 Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Once the LAMA2 pathogenic variants have been identified in an affected family member, carrier testing for at-risk relatives and prenatal and preimplantation genetic testing are possible."
    explanation: States the reproductive options this counselling delivers.
- name: Omigapil
  description: >-
    An anti-apoptotic small molecule that inhibits the GAPDH-Siah1-mediated death pathway. It is
    the only therapeutic small molecule to have reached a clinical trial in this disease. In dyW
    and dy2J mice it inhibits muscle apoptosis, reduces weight loss and skeletal deformity,
    increases locomotor activity and delays mortality. The human study (CALLISTO, NCT01805024)
    was a phase 1 open-label pharmacokinetic and safety study over twelve weeks in 20 patients
    with LAMA2- or COL6-related dystrophy; it met its primary endpoint, but it was neither
    designed nor powered to show clinical benefit, and none was observed. This is an unapproved
    investigational agent and is recorded here as the state of the therapeutic pipeline, not as
    available care.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: omigapil
      term:
        id: NCIT:C97362
        label: Omigapil
  therapeutic_modality: SMALL_MOLECULE
  target_mechanisms:
  - target: Myofibre Degeneration, Necrosis and Apoptosis
    treatment_effect: INHIBITS
    description: >-
      Inhibiting GAPDH-Siah1-mediated apoptosis reduces myofibre death in the mouse. Whether this
      translates to humans is unresolved: the only human trial was a pharmacokinetic study.
    evidence:
    - reference: PMID:19759319
      reference_title: "Omigapil ameliorates the pathology of muscle dystrophy caused by laminin-alpha2 deficiency."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Specifically, we demonstrate that treatment with omigapil inhibits apoptosis in muscle, reduces body weight loss and skeletal deformation, increases locomotive activity, and protects from early mortality."
      explanation: Demonstrates the anti-apoptotic effect on the target node and the downstream functional benefit in the mouse.
  evidence:
  - reference: PMID:19759319
    reference_title: "Omigapil ameliorates the pathology of muscle dystrophy caused by laminin-alpha2 deficiency."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Here we demonstrate that the proapoptotic glyceraldehyde-3-phosphate dehydrogenase (GAPDH)-Siah1-CBP/p300-p53 pathway is activated in a mouse model for MDC1A."
    explanation: Establishes that the pathway omigapil inhibits is actually engaged in the disease model.
  - reference: PMID:38915423
    reference_title: "Phase 1 Open-Label Study of Omigapil in Patients With LAMA2- or COL6-Related Dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In general, omigapil was safe and well tolerated."
    explanation: The safety result of the only human trial.
  - reference: PMID:38915423
    reference_title: "Phase 1 Open-Label Study of Omigapil in Patients With LAMA2- or COL6-Related Dystrophy."
    supports: NO_EVIDENCE
    evidence_source: HUMAN_CLINICAL
    snippet: "No consistent changes were seen in the disease-relevant clinical assessments during the duration of the study."
    explanation: The small phase 1 safety/pharmacokinetic study was not designed to establish
      efficacy; absence of consistent clinical change is not evidence of a definitive lack of
      treatment benefit.
  notes: >-
    Investigational only. No regulatory approval exists for omigapil in any indication.
- name: Avoidance of Succinylcholine and Statins
  description: >-
    A drug-safety measure rather than a therapy, and the one item on this list that changes
    management in an emergency department. Succinylcholine during anaesthetic induction risks
    hyperkalaemia and cardiac conduction abnormalities in this population; statins risk further
    muscle damage. Both should be recorded on an alert document.
  treatment_term:
    preferred_term: avoidance of contraindicated agents
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:22675738
    reference_title: "LAMA2 Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Succinylcholine in induction of anesthesia because of risk of hyperkalemia and cardiac conduction abnormalities; statins, cholesterol-lowering medications, because of the risk of muscle damage."
    explanation: The GeneReviews Agents/Circumstances to Avoid list, quoted verbatim.
clinical_trials:
- name: NCT01805024
  phase: PHASE_I
  status: COMPLETED
  description: CALLISTO, an ascending multiple-dose cohort study of omigapil in children and
    adolescents with congenital muscular dystrophy, establishing pharmacokinetics at three dose
    levels with safety and tolerability assessment. Twenty patients (ten LAMA2-related, ten
    COL6-related) were enrolled at the NIH. The trial met its primary pharmacokinetic endpoint;
    disease-relevant clinical assessments showed no consistent change over the twelve-week exposure,
    a period and design not intended to establish efficacy.
  target_phenotypes:
  - preferred_term: Axial muscle weakness
    term:
      id: HP:0003327
      label: Axial muscle weakness
  - preferred_term: Restrictive ventilatory defect
    term:
      id: HP:0002091
      label: Restrictive ventilatory defect
  evidence:
  - reference: clinicaltrials:NCT01805024
    reference_title: "Congenital Muscular Dystrophy Ascending Multiple Dose Cohort Study Analyzing Pharmacokinetics at Three Dose Levels In Children and Adolescents With Assessment of Safety and Tolerability of Omigapil (CALLISTO)"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The purpose of the study is to establish the pharmacokinetic profile of omigapil in paediatric and adolescent patients with CMD and to evaluate the safety and tolerability of omigapil."
    explanation: The registry record's own statement of the trial's objective.
  - reference: PMID:38915423
    reference_title: "Phase 1 Open-Label Study of Omigapil in Patients With LAMA2- or COL6-Related Dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This study represents the thus far only clinical trial of a therapeutic small molecule for LAMA2-RD and COL6-RD, completed with an adaptive trial design to arrive at dose adjustments."
    explanation: Establishes the trial's standing as the only interventional small-molecule study in this disease.
- name: NCT04299321
  phase: NOT_APPLICABLE
  status: COMPLETED
  description: >-
    A completed retrospective chart review of infants and toddlers with LAMA2-CMD (n=75). Retrospective natural-history data on the youngest patients, who are the hardest group to enrol prospectively.
  evidence:
  - reference: clinicaltrials:NCT04299321
    reference_title: "LAMA2 Retrospective Review of Medical Charts in Infants & Toddlers With LAMA2-Congenital Muscular Dystrophy"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "This retrospective chart review study of 75-120 LAMA2-CMD patients will expand the investigators understanding of the natural history of this disease."
    explanation: >-
      The registry record establishing this study's population and objective.
- name: NCT04478981
  phase: NOT_APPLICABLE
  status: COMPLETED
  description: >-
    LAST STRONG, a completed natural-history study (n=38) covering LAMA2- and SELENON-related disease together, framed around distinguishing them from mitochondrial myopathies.
  evidence:
  - reference: clinicaltrials:NCT04478981
    reference_title: "The Natural History of Patients With Congenital Muscular Dystrophies Due to Mutations in the SELENON or LAMA2 Genes: Working Towards Trial-readiness in Two Mitochondrial Myopathy Mimics"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "SEPN1 (SELENON) is a rare congenital myopathy due to mutations in the SELENON gene."
    explanation: >-
      The registry record establishing this study's population and objective.
- name: NCT06132750
  phase: NOT_APPLICABLE
  status: UNKNOWN
  description: >-
    The five-year extension of LAST STRONG (n=40). Registry status is UNKNOWN, meaning the record has not been updated within the registry's expected window - recorded as the registry reports it rather than assumed complete.
  evidence:
  - reference: clinicaltrials:NCT06132750
    reference_title: "A 5-year Natural History Study in LAMA2-related Muscular Dystrophy and SELENON-related Myopathy: the Extended LAST STRONG Study"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "SELENON-related myopathy (SELENON-RM) and LAMA2-related muscular dystrophy (LAMA2-MD) are congenital neuromuscular disorders presenting with slowly, progressive axial muscle weakness, spinal rigidity, scoliosis and respiratory insufficiency."
    explanation: >-
      The registry record establishing this study's population and objective.
- name: NCT06582537
  phase: NOT_APPLICABLE
  status: COMPLETED
  description: >-
    An ex vivo study (n=7) applying genetic correction to myogenic stem cells taken from patients. Despite the interventional-sounding title the registry classes it as observational: the correction is performed on cells, not administered to participants.
  evidence:
  - reference: clinicaltrials:NCT06582537
    reference_title: "Ex Vivo Genetic Correction of LAMA2 Mutation(s) in Myogenic Stem Cells of Patients with Merosin-deficient Congenital Muscle Dystrophy Type 1a (MDC1a)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Merosin-deficient congenital muscle dystrophy type 1a (MDC1a), or LAMA2 muscular dystrophy (LAMA2-MD) is a severe autosomal recessive form of muscular dystrophy that is caused by homozygous or compound heterozygous mutations in the laminin alpha 2 (LAMA-2) gene."
    explanation: >-
      The registry record establishing this study's population and objective.
- name: NCT06503367
  phase: NOT_APPLICABLE
  status: RECRUITING
  description: >-
    READY CMD LAMA2, a recruiting trial-readiness study in children aged 0-5 (n=44), building the outcome measures an interventional trial in this age group would need.
  evidence:
  - reference: clinicaltrials:NCT06503367
    reference_title: "Establishing Clinical Trial Readiness for Children 0-5 Years With Congenital Muscular Dystrophy Secondary to LAMA2 Mutations (READY CMD LAMA2)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The goal of this observational study is to understand how young children with LAMA2-related dystrophy move and change over time."
    explanation: >-
      The registry record establishing this study's population and objective.
animal_models:
- name: dy3K/dy3K laminin alpha2 null mouse
  species: Mouse
  genotype: Lama2 targeted null (dy3K), homozygous
  publication: PMID:31586140
  description: >-
    The complete-null mouse and the most severe of the family, dying by about three weeks. Its
    value is temporal resolution rather than fidelity of course: it is the model in which the
    sequence of early events has been mapped, showing apoptosis at postnatal day 1, full
    dystrophic architecture with inflammation and matrix deposition by day 4, peak deterioration
    at day 7, and severe involvement of the masticatory muscles that plausibly underlies the
    malnutrition and death.
  evidence:
  - reference: PMID:31586140
    reference_title: "Early skeletal muscle pathology and disease progress in the dy(3K)/dy(3K) mouse model of congenital muscular dystrophy with laminin α2 chain-deficiency."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Here, we unveil the first pathogenic events and characterise the disease development in a mouse model for LAMA2-CMD (dy3K/dy3K), by analysing muscles at perinatal, neonatal and postnatal stages."
    explanation: Establishes the model and the developmental-timing question it was used to answer.
  modeled_mechanisms:
  - target: Myofibre Degeneration, Necrosis and Apoptosis
    relationship: RECAPITULATES
    fidelity: HIGH
    model_scale: CELLULAR
    description: >-
      Reproduces the apoptotic and necrotic myofibre death of the human disease and dates its
      onset to the first postnatal day.
    limitations: >-
      The murine course is compressed into three weeks against a human course of decades, so the
      model reports the sequence of events faithfully but not their timescale. The masticatory
      involvement that dominates mortality here has no clear human counterpart as a cause of
      death.
    readouts:
    - name: Apoptotic muscle fibres at postnatal day 1
      target: Myofibre Degeneration, Necrosis and Apoptosis
      direction: INCREASED
      interpretation: Dates the onset of the apoptotic component of fibre loss.
      evidence:
      - reference: PMID:31586140
        reference_title: "Early skeletal muscle pathology and disease progress in the dy(3K)/dy(3K) mouse model of congenital muscular dystrophy with laminin α2 chain-deficiency."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "We found that apoptotic muscle fibres were present as early as postnatal day 1."
        explanation: Reports the measurement behind this readout.
    evidence:
    - reference: PMID:31586140
      reference_title: "Early skeletal muscle pathology and disease progress in the dy(3K)/dy(3K) mouse model of congenital muscular dystrophy with laminin α2 chain-deficiency."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Other typical dystrophic hallmarks (muscle degeneration, inflammation, and extensive production of the extracellular matrix proteins) were clearly evident already at postnatal day 4, and the highest degree of muscle deterioration was reached by day 7."
      explanation: Supports treating this model as informative for the degeneration node by showing it reproduces the full dystrophic picture.
  - target: Dysregulated Muscle Proteostasis and Autophagy
    relationship: RECAPITULATES
    fidelity: HIGH
    model_scale: MOLECULAR
    description: >-
      Autophagy-related gene expression is raised in dy3K/dy3K muscle, and the same upregulation
      was confirmed in human MDC1A muscle, so the model is not merely analogous here.
    limitations: >-
      The therapeutic inference rests on systemic 3-methyladenine, a non-selective
      phosphoinositide 3-kinase inhibitor, so the rescue is not a clean test of autophagy alone.
    readouts:
    - name: Autophagy-related gene expression in dystrophic muscle
      target: Dysregulated Muscle Proteostasis and Autophagy
      direction: INCREASED
      interpretation: Molecular correlate of the enhanced autophagic flux this node asserts.
      evidence:
      - reference: PMID:21920942
        reference_title: "Autophagy is increased in laminin α2 chain-deficient muscle and its inhibition improves muscle morphology in a mouse model of MDC1A."
        supports: SUPPORT
        evidence_source: OTHER
        snippet: "Using the dy(3K)/dy(3K) mouse model of laminin α2 chain deficiency and MDC1A patient muscle, we show here that expression of autophagy-related genes is upregulated in laminin α2 chain-deficient muscle."
        explanation: Reports the measurement in both mouse and human muscle.
    evidence:
    - reference: PMID:21920942
      reference_title: "Autophagy is increased in laminin α2 chain-deficient muscle and its inhibition improves muscle morphology in a mouse model of MDC1A."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Moreover, we found that autophagy inhibition significantly improves the dystrophic dy(3K)/dy(3K) phenotype."
      explanation: The intervention result that makes this model informative for the autophagy node.
- name: dyW/dyW laminin alpha2-deficient mouse
  species: Mouse
  genotype: Lama2 targeted mutation (dyW), homozygous, expressing a truncated laminin alpha2
  publication: PMID:15578095
  description: >-
    The workhorse preclinical model, expressing a small amount of truncated protein and surviving
    long enough for intervention studies. Most of the therapeutic hypotheses in this disease were
    tested here first: Bax deletion and Bcl-2 overexpression, omigapil, integrin alpha-7
    overexpression, and the mini-agrin linker. That four mechanistically unrelated interventions
    each extend survival in the same animal is the strongest single argument that the downstream
    cascade is attackable.
  evidence:
  - reference: PMID:15578095
    reference_title: "Inhibition of apoptosis improves outcome in a model of congenital muscular dystrophy."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "To examine the significance of apoptosis in CMD1A pathogenesis, we determined whether pathogenesis in laminin-alpha2-deficient (Lama2(-/-)) mice could be ameliorated by inhibiting apoptosis"
    explanation: Establishes the model and the interventional use it is cited for here.
  modeled_mechanisms:
  - target: Myofibre Degeneration, Necrosis and Apoptosis
    relationship: RECAPITULATES
    fidelity: HIGH
    model_scale: CELLULAR
    description: >-
      Apoptotic fibre death is present and is causally load-bearing: removing Bax or
      overexpressing Bcl-2 each produce a severalfold lifespan increase, and Bax inactivation also
      improves growth, histology and contractures.
    limitations: >-
      dyW mice express a truncated laminin alpha2 fragment rather than being a complete null, so
      the genotype corresponds to a severe hypomorph rather than to the biallelic-null human
      genotype it is usually taken to model.
    readouts:
    - name: Lifespan under Bax inactivation or Bcl-2 overexpression
      target: Myofibre Degeneration, Necrosis and Apoptosis
      direction: RESTORED
      interpretation: Rescue readout establishing apoptosis as a causal contributor rather than an epiphenomenon.
      evidence:
      - reference: PMID:15578095
        reference_title: "Inhibition of apoptosis improves outcome in a model of congenital muscular dystrophy."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "We found that both of these genetic interventions produced a several-fold increase in the lifespan of Lama2(-/-) mice."
        explanation: Reports the survival measurement behind this readout.
    evidence:
    - reference: PMID:15578095
      reference_title: "Inhibition of apoptosis improves outcome in a model of congenital muscular dystrophy."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Bax inactivation also improved postnatal growth rate and myofiber histology and decreased fixed contractures of Lama2(-/-) mice."
      explanation: Shows the rescue extends to histology and contracture, not survival alone.
  - target: Failure of Basal Lamina to Sarcolemma Receptor Coupling
    relationship: PERTURBS
    fidelity: MODERATE
    model_scale: MOLECULAR
    description: >-
      Used as the test bed for restoring the coupling directly. Transgenic mini-agrin, which binds
      dystroglycan but not integrin alpha-7-beta-1, and a perlecan-derived chimeric protein each
      ameliorate the disease, including when expression is started late. Separately, transgenic
      integrin alpha-7 overexpression restores sarcolemmal alpha-7-beta-1 and improves pathology
      and life expectancy. Together these attack the two arms of the lost linkage independently.
    limitations: >-
      Both are transgenic overexpression experiments in the mouse, not deliverable therapies, and
      neither restores laminin-211 itself. The mini-agrin construct rebuilds only the dystroglycan
      arm and the integrin transgene only the integrin arm, so neither is a complete substitution.
    readouts:
    - name: Lifespan and health under mini-agrin or perlecan-chimera expression
      target: Failure of Basal Lamina to Sarcolemma Receptor Coupling
      direction: RESTORED
      interpretation: Rescue by re-linking the basement membrane to dystroglycan, which is the specific coupling this node reports as lost.
      evidence:
      - reference: PMID:17389231
        reference_title: "Linker molecules between laminins and dystroglycan ameliorate laminin-alpha2-deficient muscular dystrophy at all disease stages."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Now we show that late-onset expression of mini-agrin still prolongs life span and improves overall health, although not to the same extent as early expression."
        explanation: Reports the survival and health measurement behind this readout, including its dependence on timing.
    evidence:
    - reference: PMID:17389231
      reference_title: "Linker molecules between laminins and dystroglycan ameliorate laminin-alpha2-deficient muscular dystrophy at all disease stages."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "These experiments are conceptual proof that linking the basement membrane to dystroglycan by specifically designed molecules or by endogenous ligands, could be a means to counteract MDC1A at a progressed stage of the disease, and thus opens new possibilities for the development of treatment options for this muscular dystrophy."
      explanation: The authors' own statement that the rescue works by restoring the matrix-to-dystroglycan link, which is what makes this model informative for the coupling node.
    - reference: PMID:21652631
      reference_title: "Transgenic overexpression of the α7 integrin reduces muscle pathology and improves viability in the dy(W) mouse model of merosin-deficient congenital muscular dystrophy type 1A."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Enhanced expression of the α7 integrin restored sarcolemmal localization of the α7β1 integrin to laminin-α2-deficient myofibers, changed the composition of the muscle extracellular matrix, reduced muscle pathology, maintained muscle strength and function and improved the life expectancy of dy(W⁻/⁻) mice."
      explanation: Establishes the integrin arm of the same rescue, independently of the dystroglycan arm.
- name: dy2J/dy2J splice-mutant mouse
  species: Mouse
  genotype: Lama2 dy2J splice-site mutation, homozygous
  publication: PMID:31341277
  description: >-
    A partial-deficiency model, carrying a splice mutation that yields a truncated but partly
    functional protein, with a milder and longer course. It is the natural model for the
    limb-girdle subtype and the one in which reversibility has been shown: CRISPR-dCas9
    upregulation of the paralogous Lama1 improved and partly reversed established fibrosis and
    hindlimb paralysis when started in symptomatic animals, against the prior expectation that
    fibrotic change is irreversible.
  evidence:
  - reference: PMID:31341277
    reference_title: "A mutation-independent approach for muscular dystrophy via upregulation of a modifier gene."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We modulate expression of Lama1 in the dy2j/dy2j mouse model of MDC1A using an adeno-associated virus (AAV9) carrying a catalytically inactive Cas9 (dCas9), VP64 transactivators and single-guide RNAs that target the Lama1 promoter."
    explanation: Establishes the model and the intervention it was used to test.
  modeled_mechanisms:
  - target: Endomysial Fibrosis and Replacement of Muscle
    relationship: RESCUES
    fidelity: MODERATE
    model_scale: TISSUE
    description: >-
      Upregulating the paralogous laminin-alpha1 prevented fibrosis and paralysis when given
      pre-symptomatically, and improved and partly reversed both when given after they were
      established.
    limitations: >-
      The rescue is by a paralogous laminin substituting for the missing one, not by restoring
      laminin-alpha2, so it tests the reversibility of the downstream fibrosis rather than the
      correction of the primary lesion. dy2J is a partial-deficiency allele, so the result speaks
      most directly to the milder end of the human spectrum. A companion study in a
      complete-deletion model found high-dose mortality and non-sustained expression, which the
      dy2J experiment did not surface.
    readouts:
    - name: Muscle fibrosis and hindlimb paralysis after Lama1 upregulation
      target: Endomysial Fibrosis and Replacement of Muscle
      direction: RESTORED
      interpretation: Reversal of established fibrotic change, which is the claim this link records.
      evidence:
      - reference: PMID:31341277
        reference_title: "A mutation-independent approach for muscular dystrophy via upregulation of a modifier gene."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "However, we show that dystrophic features and disease progression were improved and reversed when the treatment was initiated in symptomatic dy2j/dy2j mice with apparent hindlimb paralysis and muscle fibrosis."
        explanation: Reports the reversal measurement behind this readout.
    evidence:
    - reference: PMID:31341277
      reference_title: "A mutation-independent approach for muscular dystrophy via upregulation of a modifier gene."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "When pre-symptomatic mice were treated, Lama1 was upregulated in skeletal muscles and peripheral nerves, which prevented muscle fibrosis and paralysis."
      explanation: Establishes the preventive arm of the rescue alongside the reversal arm.
    - reference: PMID:38777118
      reference_title: "Lama1 upregulation prolongs the lifespan of the dy(H)/dy(H) mouse model of LAMA2-related congenital muscular dystrophy."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Additionally, we reveal the limitations of LAMA1 upregulation, including high-dose mortality and non-sustained expression, which require further optimization in future studies."
      explanation: The independent limitation recorded against this strategy, from a different Lama2 model.
- name: lama2 mutant zebrafish
  species: Zebrafish
  genotype: lama2 loss of function
  publication: PMID:31754462
  description: >-
    An optically accessible model used for live fibre tracking and mechanistic perturbation.
    Live tracking of individual fibres showed that detachment is not immediately
    lethal, since detached fibres retain sarcolemmal integrity and attempt reattachment,
    extension and fusion before dying, which reframed the disease as having a window in which a
    detached fibre can be re-functionalised.
  evidence:
  - reference: PMID:31754462
    reference_title: "Cellular rescue in a zebrafish model of congenital muscular dystrophy type 1A."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "a process we show can be achieved by muscle specific or systemic Laminin delivery"
    explanation: States the rescue the model demonstrates, which is what establishes it as an interventional as well as an observational system.
  modeled_mechanisms:
  - target: Contraction-Induced Myofibre Detachment and Mechanical Injury
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: CELLULAR
    description: >-
      Reproduces myofibre detachment from the basal lamina and, uniquely, allows it to be watched
      in a living animal fibre by fibre.
    limitations: >-
      Zebrafish larval muscle is anatomically and mechanically unlike mammalian limb muscle, and
      the observations are made over hours in a larva rather than over years in a child, so the
      delay between detachment and death cannot be assumed to have the same duration in humans.
      In the separate Candyfloss BTS experiment, contraction inhibition began before spontaneous
      movement and also impaired normal muscle development. Washout was followed by structural
      damage in mutants and partial force recovery in siblings; this does not establish that
      immobilization benefits human MDC1A.
    readouts:
    - name: Sarcolemmal integrity and remodelling of detached fibres
      target: Contraction-Induced Myofibre Detachment and Mechanical Injury
      direction: ALTERED
      interpretation: Direct observation of the detachment event and of what the fibre does afterwards.
      evidence:
      - reference: PMID:31754462
        reference_title: "Cellular rescue in a zebrafish model of congenital muscular dystrophy type 1A."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "Here we show, via live tracking of individual muscle fibres, that dystrophic myofibres in the zebrafish model of MDC1A maintain sarcolemmal integrity and undergo dynamic remodelling behaviours post detachment, including focal sarcolemmal reattachment, cell extension and hyper-fusion with surrounding myoblasts."
        explanation: Reports the live-imaging measurement behind this readout.
    - name: Structural damage after contraction inhibition and washout
      target: Contraction-Induced Myofibre Detachment and Mechanical Injury
      direction: ALTERED
      interpretation: Early BTS exposure reduces structural damage; after one day of washout,
        Candyfloss mutants develop patchy birefringence defects and remain weaker than siblings.
        Normal-sibling force only partly recovers. This is a larval perturbation result, not
        evidence that immobilization restores normal muscle function in patients.
      evidence:
      - reference: PMID:26536238
        reference_title: Immobilization of Dystrophin and Laminin α2-Chain Deficient Zebrafish Larvae
          In Vivo Prevents the Development of Muscular Dystrophy.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: In contrast, the Caf larvae at 5dpf were weaker than their siblings (right diagram, Panel
          D, Fig 5) and developed structural changes with patchy alterations in birefringence (Panel C,
          Fig 5). These data suggest that active movement improves the mechanical function after BTS immobilization
          in the Caf sibling group, but also introduces structural changes in the Caf mutants.
        explanation: The washout arm supports renewed activity-associated damage in the laminin-alpha2-deficient
          Candyfloss strain. Sapje dystrophin mutants behaved differently after washout; strain activity
          and mutation-specific susceptibility may both contribute.
datasets:
- accession: geo:GSE253680
  title: Transcriptomic analysis of fetal epaxial muscle fibers from wildtype and dyW/dyW mice at embryonic day 17.5
  description: >-
    Fetal muscle-fibre transcriptomes from dyW/dyW and wild-type mice at embryonic day 17.5, the
    point at which disease onset has been placed in this model. It is the dataset that speaks
    most directly to the entry's claim that the pathology begins before birth rather than
    accumulating after it.
  data_type: BULK_RNA_SEQ
  sample_count: 7
  organism:
    preferred_term: house mouse
    term:
      id: NCBITaxon:10090
      label: Mus musculus
  genes:
  - preferred_term: LAMA2
    term:
      id: hgnc:6482
      label: LAMA2
  publication: PMID:39379105
  evidence:
  - reference: GEO:GSE253680
    reference_title: Transcriptomic analysis of fetal epaxial muscle fibers from wildtype and dyW/dyW mice at embryonic day 17.5
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "However, it is not yet known what mechanisms are faulty, right at disease onset, which in the mouse model of LAMA2-CMD dyW/dyW has been previously established to occur between embryonic days (E) 17.5 and E18.5."
    explanation: The repository summary dates disease onset in this model to late gestation, which is what makes the dataset relevant to the prenatal-onset claim in the neonatal progression phase.
- accession: geo:GSE126416
  title: RNA-deep sequencing (RNA-Seq) analysis of dy2J/dy2J (Lama2-CMD mouse model), mdx (DMD mouse model) and Wild-type skeletal muscles
  description: >-
    Whole-transcriptome profiling of dy2J/dy2J skeletal muscle at eight weeks against mdx and
    wild-type. The mdx comparison is what makes it useful here: it separates what is shared with
    a sarcolemmal dystrophy generally from what is specific to laminin-alpha2 deficiency, and the
    specific finding is a downregulated rather than upregulated regeneration programme.
  data_type: BULK_RNA_SEQ
  sample_count: 8
  organism:
    preferred_term: house mouse
    term:
      id: NCBITaxon:10090
      label: Mus musculus
  genes:
  - preferred_term: LAMA2
    term:
      id: hgnc:6482
      label: LAMA2
  publication: PMID:31348492
  evidence:
  - reference: GEO:GSE126416
    reference_title: "RNA-deep sequencing (RNA-Seq) analysis of dy2J/dy2J (Lama2-CMD mouse model), mdx (DMD mouse model) and Wild-type skeletal muscles"
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Interestingly, significant downregulation of Pax7 was detected in dy2J/dy2J compared to upregulation of this key regeneration gene in mdx mice."
    explanation: Supports the Abortive Muscle Regeneration node with a transcriptomic contrast showing the regenerative programme is suppressed in laminin-alpha2 deficiency where it is driven in a dystrophin-deficient control.
  - reference: GEO:GSE126416
    reference_title: "RNA-deep sequencing (RNA-Seq) analysis of dy2J/dy2J (Lama2-CMD mouse model), mdx (DMD mouse model) and Wild-type skeletal muscles"
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Enrichment pathway analysis using Ingenuity Pathway Analysis (IPA) showed enrichment of inflammation, fibrosis, cellular movement, migration and proliferation of cells, apoptosis and necrosis in both mouse models"
    explanation: Independently recovers the inflammation, fibrosis and apoptosis arms of the curated pathophysiology chain from an unbiased transcriptomic analysis.
- accession: geo:GSE307443
  title: Loss of cell-autonomously secreted laminin-α2 drives muscle stem cell dysfunction in LAMA2-related muscular dystrophy
  description: >-
    Human iPSC-derived myogenic precursor cells, LAMA2-deficient versus control. One of the few
    human-cell datasets in this disease, and directly relevant to the Abortive Muscle Regeneration
    node because it addresses whether laminin-alpha2 acts on the progenitor cell itself rather
    than only on the mature fibre.
  data_type: BULK_RNA_SEQ
  sample_count: 8
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  genes:
  - preferred_term: LAMA2
    term:
      id: hgnc:6482
      label: LAMA2
  publication: PMID:41309582
  notes: >-
    Recorded without an evidence block. The repository summary states the study's motivation
    rather than its result, so there is no sentence in the cached record that would substantively
    support a specific curated claim; quoting the motivation would be a topic snippet rather than
    a finding.
- accession: geo:GSE3252
  title: Laminin-deficient muscular dystrophy, dy/dy diaphragm
  description: Microarray profiling of eight-week-old dy/dy mouse diaphragm. It samples respiratory
    muscle pathology in a model; prominent functional diaphragm failure is not established as
    the driver of human MDC1A respiratory decline, where intercostal and accessory weakness
    is important.
  data_type: MICROARRAY
  sample_count: 8
  organism:
    preferred_term: house mouse
    term:
      id: NCBITaxon:10090
      label: Mus musculus
  genes:
  - preferred_term: LAMA2
    term:
      id: hgnc:6482
      label: LAMA2
  publication: PMID:16368874
  notes: >-
    The dataset-discovery tool tagged this GENE_ONLY, meaning the match ran through the gene name
    rather than the disease name. Triaged manually and kept: the GEO title and summary both name
    laminin/merosin-deficient muscular dystrophy in the dy/dy mouse, so it is a true positive that
    the disease-name matcher missed because the record predates the LAMA2-CMD nomenclature.
epidemiology:
- name: Share of congenital muscular dystrophy
  description: >-
    LAMA2-related congenital muscular dystrophy is one of the most common congenital muscular
    dystrophies worldwide, though the share varies by population: around a third to a half of
    congenital muscular dystrophy in the sources aggregated by one large cohort study, roughly
    30% in Europe against 6% in Japan in another review's figures.
  evidence:
  - reference: PMID:34281576
    reference_title: "Natural history and genetic study of LAMA2-related muscular dystrophy in a large Chinese cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "LAMA2-CMD is one of the most common congenital muscular dystrophies (CMDs) in the world, accounting for 36.4%-48% of CMD patients"
    explanation: Gives the aggregate share of congenital muscular dystrophy.
  - reference: PMID:31308722
    reference_title: "Current understanding and treatment of cardiac and skeletal muscle pathology in laminin-α2 chain-deficient congenital muscular dystrophy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Early-onset LAMA2 MD is the most common form of congenital muscular dystrophy (CMD) globally, affecting about 30% of the CMD patients in Europe and 6% of the patients in Japan."
    explanation: Gives the between-population variation in that share.
- name: Geographic variation in reported prevalence
  description: >-
    Published prevalence estimates for LAMA2-related dystrophy span nearly twenty-fold between
    countries, from 0.14 to 2.5 per 100,000. This is far more likely to reflect ascertainment and
    registry completeness than a real biological gradient, and it is the reason this entry records
    a coarse prevalence band rather than treating any point estimate as authoritative.
  evidence:
  - reference: PMID:39213089
    reference_title: "A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related Muscular Dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Reported prevalence varies widely between 0.14 : 100 000 (Italy) and 2.5 : 100 000 (Sweden)"
    explanation: States the range of published estimates that motivates the caution recorded here.
- name: Share of limb-girdle muscular dystrophy
  description: >-
    At the milder end, partial merosin deficiency (LGMDR23) is a small but real share of the
    limb-girdle population, 2.3% in a Danish series, which is the practical argument for
    checking merosin status in unexplained limb-girdle weakness with white-matter change.
  evidence:
  - reference: PMID:31308722
    reference_title: "Current understanding and treatment of cardiac and skeletal muscle pathology in laminin-α2 chain-deficient congenital muscular dystrophy."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "One study in Denmark revealed that late-onset LAMA2 MD accounts for 2.3% of the limb girdle-type muscular dystrophy cases."
    explanation: Gives the share of limb-girdle muscular dystrophy attributable to partial merosin deficiency.
differential_diagnoses:
- name: Merosin-positive congenital muscular dystrophy
  description: >-
    The historical first fork: congenital muscular dystrophy with preserved merosin staining.
    Motor nerve conduction is normal and brain white matter is typically normal, so the two
    supportive tests that are abnormal in MDC1A are the ones that separate them.
  evidence:
  - reference: PMID:8576559
    reference_title: "Demyelinating peripheral neuropathy in merosin-deficient congenital muscular dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All but two of the 10 merosin-deficient cases had reduced motor nerve conduction, whereas all the merosin-positive cases had normal results."
    explanation: Shows the electrophysiological separation between the merosin-deficient and merosin-positive groups.
- name: Dystroglycanopathies with brain malformation
  description: >-
    Fukuyama congenital muscular dystrophy, muscle-eye-brain disease and Walker-Warburg syndrome
    also produce congenital muscular dystrophy with cobblestone cortex, and they converge on the
    same pial basement membrane failure, but from the receptor side, through defective
    alpha-dystroglycan glycosylation, rather than from the ligand side. MDC1A was classically
    distinguished as the congenital muscular dystrophy without structural CNS involvement, which
    is now known to be only mostly true.
  evidence:
  - reference: PMID:32827036
    reference_title: "Cobblestone Malformation in LAMA2 Congenital Muscular Dystrophy (MDC1A)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "It is the most common cause of what was originally called classical, or occidental, CMD without structural involvement of the central nervous system (CNS) in distinction to CMDs with CNS involvement (Fukuyama CMD, muscle-eye-brain disease, and Walker-Warburg syndrome)"
    explanation: States the classical nosological distinction and names the dystroglycanopathies it separates MDC1A from.
- name: Limb-girdle muscular dystrophies
  description: >-
    For the partial-deficiency subtype the differential is the limb-girdle group generally.
    Partial merosin deficiency has been misdiagnosed as Duchenne and as unclassified limb-girdle
    dystrophy for years before slowed nerve conduction and white-matter change on MRI redirected
    the workup, which is the practical reason to check merosin in that setting.
  evidence:
  - reference: PMID:9829280
    reference_title: "Laminin alpha 2-chain gene mutations in two siblings presenting with limb-girdle muscular dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Partial laminin alpha 2 deficiency should be considered in the differential diagnosis of limb-girdle muscular dystrophy."
    explanation: States the recommendation this differential records.
  - reference: PMID:9131648
    reference_title: "Late onset muscular dystrophy with cerebral white matter changes due to partial merosin deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Merosin status should be assessed in patients with late-onset limb girdle muscular dystrophy."
    explanation: Independent statement of the same recommendation from a separate late-onset family.
notes: >-
  Scope and lumping. This entry covers the whole LAMA2 allelic series, with complete deficiency
  (the congenital severe form the MONDO term names) and partial deficiency (LGMDR23) curated as
  `has_subtypes` rather than as separate entries. They share one gene, one protein, one
  mechanism and one pathograph, differing in the dose of residual laminin alpha-2, so splitting
  them would duplicate the entire mechanism section to express a quantitative difference. Where a
  statement in this file is not marked with a `subtype`, read it as describing complete
  deficiency, which is the phenotype the MONDO term names and the one the literature calls MDC1A.
  Note that `stubs/Muscular_Dystrophy_Limb-girdle_Autosomal_Recessive_23.yaml` remains an open
  stub at the time of writing; whoever picks it up should read it against this entry's partial
  deficiency subtype before creating a second entry for the same allelic series.

  Where the residual-protein rule breaks. The complete-versus-partial rule is a strong tendency,
  not a law, and the literature contains its own counterexamples. Complete laminin alpha-2
  deficiency with a mild course has been reported, including a homozygous stop-codon patient
  described as having a mild evolution; and merosin quantity on biopsy is explicitly stated not
  to predict phenotype in an individual. Seizures cut against the gradient outright, being
  reported in 35.7% of the milder LGMDR23 group against 9.5% of the congenital group in the same
  cohort. So do not treat the biopsy stain as prognostic, and do not assume the CNS features
  scale with the muscle ones.

  Two independent CNS lesions, not one. The near-universal white-matter signal change and the
  minority cortical malformation have different mechanisms, different frequencies and different
  clinical weight, and they are curated as separate pathophysiology branches for that reason. The
  white-matter change is attributed to increased water content following loss of laminin from
  perivascular basement membranes; it is essentially always present and essentially always silent.
  The cortical malformation follows a focal breach of the glia limitans, is present in around a
  fifth, and is what carries the epilepsy and intellectual disability. Conflating them would
  predict cognitive impairment in nearly every patient, which is the opposite of what is observed.

  Module conformance. Three conformances are declared. `fibrotic_response#Excessive ECM
  Deposition` on the endomysial fibrosis node is straightforward.
  `pial_basement_membrane_radial_glial_endfoot_failure#Pial Basement Membrane Assembly Failure` is
  the interesting one: that module's other conformers reach the same pial boundary failure through
  defective alpha-dystroglycan glycosylation, and this entry reaches it from the opposite side of
  the same bond by removing the laminin ligand, which is exactly the generic-to-specific
  substitution conformance is for. `schwann_cell_myelin_maintenance#Dysmyelination and Segmental
  Demyelination of Peripheral Nerve` is declared on the outcome node rather than the trigger node,
  and the reason is recorded in that node's own `notes`.

  What is not curated here. Muscle MRI shows a characteristic pattern with relative sparing of
  sartorius and gracilis, and muscle ultrasound echogenicity is proposed as an outcome measure;
  neither is recorded as an `imaging_findings` block because the entry's diagnostic weight sits on
  brain MRI and genetic testing. Serum and urine biomarker work exists but is exploratory and has
  no established analyte, so no `biochemical` block is curated rather than one built on a
  candidate. No `environmental` entry is curated: this is a fully penetrant Mendelian disorder and
  no exposure has been reported to modify it.

  Therapeutic landscape. Nothing is approved. The preclinical picture is unusual in that several
  mechanistically distinct interventions, namely Bcl-2 family manipulation, GAPDH-Siah1
  inhibition, autophagy inhibition, engineered dystroglycan linkers, integrin alpha-7
  overexpression, and laminin-alpha1 upregulation, each extend survival in laminin-alpha2-deficient
  mice. Read positively, that says the cascade is attackable at many points. Read cautiously, it
  says the mouse is easy to rescue, and the single completed human trial was a phase 1
  pharmacokinetic study that showed no clinical change over twelve weeks and was not designed to.
references:
- reference: PMID:26536238
  title: Immobilization of Dystrophin and Laminin α2-Chain Deficient Zebrafish Larvae In Vivo Prevents the Development of Muscular Dystrophy.
- reference: PMID:22675738
  title: "LAMA2 Muscular Dystrophy."
  tags:
  - GeneReviews
- reference: PMID:7550355
  title: "Mutations in the laminin alpha 2-chain gene (LAMA2) cause merosin-deficient congenital muscular dystrophy."
- reference: PMID:8576559
  title: "Demyelinating peripheral neuropathy in merosin-deficient congenital muscular dystrophy."
- reference: PMID:8830776
  title: "Merosin and laminin in myogenesis; specific requirement for merosin in myotube stability and survival."
- reference: PMID:9131648
  title: "Late onset muscular dystrophy with cerebral white matter changes due to partial merosin deficiency."
- reference: PMID:9829280
  title: "Laminin alpha 2-chain gene mutations in two siblings presenting with limb-girdle muscular dystrophy."
- reference: PMID:12661054
  title: "Dysmyelinating sensory-motor neuropathy in merosin-deficient congenital muscular dystrophy."
- reference: PMID:15578095
  title: "Inhibition of apoptosis improves outcome in a model of congenital muscular dystrophy."
- reference: PMID:17389231
  title: "Linker molecules between laminins and dystroglycan ameliorate laminin-alpha2-deficient muscular dystrophy at all disease stages."
- reference: PMID:18406646
  title: "LAMA2 stop-codon mutation: merosin-deficient congenital muscular dystrophy with occipital polymicrogyria, epilepsy and psychomotor regression."
- reference: PMID:19759319
  title: "Omigapil ameliorates the pathology of muscle dystrophy caused by laminin-alpha2 deficiency."
- reference: PMID:21652631
  title: "Transgenic overexpression of the α7 integrin reduces muscle pathology and improves viability in the dy(W) mouse model of merosin-deficient congenital muscular dystrophy type 1A."
- reference: PMID:21798088
  title: "Skeletal muscle laminin and MDC1A: pathogenesis and treatment strategies."
- reference: PMID:21920942
  title: "Autophagy is increased in laminin α2 chain-deficient muscle and its inhibition improves muscle morphology in a mouse model of MDC1A."
- reference: PMID:31308722
  title: "Current understanding and treatment of cardiac and skeletal muscle pathology in laminin-α2 chain-deficient congenital muscular dystrophy."
- reference: PMID:31341277
  title: "A mutation-independent approach for muscular dystrophy via upregulation of a modifier gene."
- reference: PMID:31586140
  title: "Early skeletal muscle pathology and disease progress in the dy(3K)/dy(3K) mouse model of congenital muscular dystrophy with laminin α2 chain-deficiency."
- reference: PMID:31754462
  title: "Cellular rescue in a zebrafish model of congenital muscular dystrophy type 1A."
- reference: PMID:32457577
  title: "A Family of Laminin α2 Chain-Deficient Mouse Mutants: Advancing the Research on LAMA2-CMD."
- reference: PMID:32827036
  title: "Cobblestone Malformation in LAMA2 Congenital Muscular Dystrophy (MDC1A)."
- reference: PMID:32848593
  title: "LAMA2-Related Dystrophies: Clinical Phenotypes, Disease Biomarkers, and Clinical Trial Readiness."
- reference: PMID:32910545
  title: "LAMA2-related muscular dystrophy: Natural history of a large pediatric cohort."
- reference: PMID:34281576
  title: "Natural history and genetic study of LAMA2-related muscular dystrophy in a large Chinese cohort."
- reference: PMID:35203715
  title: "Oxidative Stress, Inflammation and Connexin Hemichannels in Muscular Dystrophies."
- reference: PMID:37182895
  title: "Brain MRI Abnormalities, Epilepsy and Intellectual Disability in LAMA2 Related Dystrophy - a Genotype/Phenotype Correlation."
- reference: PMID:37476021
  title: "LAMA2-Related Muscular Dystrophy Across the Life Span: A Cross-sectional Study."
- reference: PMID:38777118
  title: "Lama1 upregulation prolongs the lifespan of the dy(H)/dy(H) mouse model of LAMA2-related congenital muscular dystrophy."
- reference: PMID:38915423
  title: "Phase 1 Open-Label Study of Omigapil in Patients With LAMA2- or COL6-Related Dystrophy."
- reference: PMID:39213089
  title: "A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related Muscular Dystrophy."
- reference: clinicaltrials:NCT01805024
  title: "Congenital Muscular Dystrophy Ascending Multiple Dose Cohort Study Analyzing Pharmacokinetics at Three Dose Levels In Children and Adolescents With Assessment of Safety and Tolerability of Omigapil (CALLISTO)"
discussions:
- kind: KNOWLEDGE_GAP
  attaches_to:
  - phenotypes#Ophthalmoparesis
  - phenotypes#Macroglossia
  - phenotypes#Gastroesophageal reflux
  - phenotypes#Reduced bone mineral density
  - phenotypes#Spinal rigidity
  - phenotypes#Neck rigidity
  - phenotypes#Hip dislocation
  - phenotypes#Pectus excavatum
  - phenotypes#Pectus carinatum
  - phenotypes#Weak cry
  discussion_id: mdc1a-gap-1
  prompt: Residual clinical attribution and model translation
  notes: The clinical findings are documented, but the reviewed sources do not establish a specific
    upstream causal route for each. Extraocular muscle involvement differs between mouse models
    and human ophthalmoparesis; tongue enlargement is not explained by a demonstrated tissue
    mechanism. Low bone density may have several determinants, and the cohort did not establish
    immobility as its sole cause. Reflux, neck and spine rigidity, hip and chest deformities,
    and weak cry have incompletely resolved contributions from muscle injury, fibrosis, posture
    or other factors. A qualified model-supported masticatory injury pathway is represented,
    but it does not establish the relative human contribution of muscle weakness, contracture
    and tongue enlargement. Supported oral-phase, nutritional and respiratory consequences are
    represented separately.
- kind: KNOWLEDGE_GAP
  attaches_to:
  - phenotypes#Pontine hypoplasia
  - phenotypes#Enlarged cisterna magna
  - phenotypes#Blake pouch cyst
  evidence:
  - reference: PMID:39213089
    reference_title: A Multicenter Cross-Sectional Study of the Swiss Cohort of LAMA2-Related
      Muscular Dystrophy.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Three out of four patients with epilepsy showed structural abnormalities on brain
      MRI (pontine hypoplasia = 3, Blake’s pouch cyst = 1, and mega cisterna magna = 1) but
      these abnormalities are not associated with epilepsy; only two of the patients had cortical
      malformations.
    explanation: The authors distinguish posterior-fossa/brainstem abnormalities from potentially
      epileptogenic cortical lesions.
  discussion_id: mdc1a-gap-2
  prompt: Posterior fossa developmental abnormalities
  notes: Pontine hypoplasia and posterior-fossa configuration abnormalities are documented in
    the Swiss imaging cohort, but their specific developmental connection to LAMA2 loss was
    not established. Cortical overmigration cannot automatically be extended to these anatomically
    distinct findings. A case-specific cyst-to-hydrocephalus relation is represented; these
    findings are not assumed to explain seizures.

📚

References & Deep Research

References

PMID:26536238

Immobilization of Dystrophin and Laminin α2-Chain Deficient Zebrafish Larvae In Vivo Prevents the Development of Muscular Dystrophy.