🧠 648.6 · Brain Malformations and Muscle Development (α-Dystroglycanopathies)

Nelson Textbook of Pediatrics 22nd Edition β€” Dystroglycanopathies: defects in O-glycosylation of Ξ±-dystroglycan. Walker-Warburg syndrome, Fukuyama CMD, Muscle-Eye-Brain disease. Genes: POMT1, POMT2, POMGnT1, FKRP, FKTN, LARGE, ISPD. Cobblestone lissencephaly, cerebellar hypoplasia, eye anomalies, elevated CK.

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πŸ“‹ 30 Clinical Scenarios β€” Brain Malformations & Muscle Development

πŸ“‡ High‑Yield Review Cards β€” Ξ±-Dystroglycanopathies

🩺 Clinical Recognition: Dystroglycanopathies (Brain-Eye-Muscle)

Select a presentation for diagnostic clues and management.

πŸ“‹ Stepwise Approach to Ξ±-Dystroglycanopathies

    ⚑ Reflex Prompts β€” Clinical Decisions in Dystroglycanopathies

    🧬 Genetics & Key Table β€” Ξ±-Dystroglycanopathies

    DisorderGene(s)InheritanceBrain FindingsEye FindingsMuscle CKSeverity
    Walker-Warburg syndromePOMT1, POMT2, POMGnT1, FKTN, FKRP, LARGE, ISPD, etc.ARCobblestone lissencephaly (type II), hydrocephalus, cerebellar hypoplasia, brainstem kinkRetinal dysplasia, microphthalmia, cataracts, glaucomaElevated (1000s)Severe; death in infancy
    Muscle-Eye-Brain disease (MEB)POMGnT1 (most common), also POMT1, POMT2, FKRP, FKTNARPolymicrogyria, pachygyria, cerebellar hypoplasia, hydrocephalusRetinal hypoplasia, myopia, cataracts, glaucomaElevatedSevere; intellectual disability, seizures
    Fukuyama CMDFKTN (fukutin)ARPolymicrogyria, cerebellar cysts, white matter changesRetinal changes, myopia (less severe than WWS)Elevated (1000s)Moderate-severe; cardiomyopathy common
    CMD with secondary merosin deficiency (LGMD2I phenotype)FKRPARNormal to mild cognitive impairment; cerebellar cysts possibleNormal to mild myopiaElevatedVariable (severe CMD to mild LGMD)
    CMD with brain and eye involvementLARGE, ISPD, GTDC2, B3GALNT2, B3GNT1, DPM1-3, GMPPB, DOLKARCobblestone lissencephaly to polymicrogyria, white matter changesVariableElevatedVariable
    πŸ”¬ Pathophysiology

    Ξ±-Dystroglycan (Ξ±-DG) is heavily glycosylated (O-mannosylation). Hypoglycosylation reduces binding to extracellular matrix proteins (laminin, agrin, perlecan, neurexin). Defects cause cobblestone lissencephaly (overmigration of neurons), cerebellar hypoplasia, retinal dysplasia, and muscular dystrophy.

    Diagnostic clue: Muscle biopsy shows reduced immunoreactivity to antibodies that recognize glycosylated Ξ±-DG (VIA4-1, IIH6). Serum CK elevated.

    Differential: Isolated CMD without brain involvement (LAMA2, COL6), congenital myopathies, peroxisomal disorders.

    Data from Nelson 648.6; Taniguchi-Ikeda M, et al. Mechanistic aspects of Ξ±-dystroglycan. Mol Aspects Med. 2016.

    πŸ“– Summary: Brain Malformations and Muscle Development β€” Nelson 648.6