Muscular Dystrophies
Muscular dystrophies are a group of inherited disorders characterised by progressive muscle weakness and wasting.
They differ in onset, genetic cause, severity, and prognosis. Early diagnosis is vital for supportive management and family counselling.
🧒 Duchenne Muscular Dystrophy (DMD)
- Onset: Early childhood (2–5 years)
- Features: Progressive weakness, difficulty walking, Gowers’ sign, scoliosis, cardiomyopathy.
- Genetics: Mutation in the DMD gene → complete loss of dystrophin (X-linked recessive).
- Management: Physical therapy, corticosteroids (prednisone), cardiac monitoring, gene therapy in development.
- Prognosis: Progressive disability; life expectancy improving with care (30s–40s).
👦 Becker Muscular Dystrophy (BMD)
- Onset: Adolescence or early adulthood.
- Features: Similar to DMD but milder; proximal weakness.
- Genetics: Mutation in DMD gene → partially functional dystrophin.
- Management: Physiotherapy, corticosteroids, cardiac support.
- Prognosis: Slower progression than DMD, near-normal lifespan possible.
👨 Myotonic Dystrophy
- Onset: Early adulthood (20s–30s).
- Features: Myotonia (delayed relaxation), muscle stiffness, cataracts, arrhythmias.
- Genetics: Expansion of repeats in DMPK (type 1) or CNBP (type 2). Autosomal dominant.
- Management: Symptomatic (myotonia treatment, pacemakers if cardiac involvement), physio.
- Prognosis: Variable; type 1 more severe, type 2 milder.
💪 Limb-Girdle Muscular Dystrophy (LGMD)
- Onset: Childhood to early adulthood.
- Features: Weakness of hip and shoulder girdle muscles → difficulty climbing stairs, lifting objects.
- Genetics: Many subtypes (e.g., CAPN3, DYSF), inheritance autosomal recessive or dominant.
- Management: Physio, OT, supportive care.
- Prognosis: Variable; some slowly progressive with good outcomes, others more disabling.
🙂 Facioscapulohumeral Muscular Dystrophy (FSHD)
- Onset: Adolescence or early adulthood.
- Features: Weakness in face, shoulders, upper arms; winged scapula.
- Genetics: Deletion in regulatory region of DUX4 on chromosome 4 (autosomal dominant).
- Management: Physio, OT, supportive aids.
- Prognosis: Slow progression; many remain independent.
👶 Congenital Muscular Dystrophy (CMD)
- Onset: Birth or early infancy.
- Features: Severe weakness from birth, contractures, delayed motor milestones.
- Genetics: Multiple genes (e.g., LAMA2, COL6A1), often autosomal recessive.
- Management: Physio, orthopaedic interventions, multidisciplinary supportive care.
- Prognosis: Very variable – some achieve walking, others have severe disability.
💡 Teaching Pearl
A key difference between Duchenne and Becker is the degree of dystrophin dysfunction: absent in DMD (severe) vs. partially functional in BMD (milder).
Always consider cardiac involvement across muscular dystrophies - it’s a major determinant of long-term outcomes.
