Duchenne Muscular Dystrophy (DMD)

Pathophysiology

• X-linked recessive mutation in the DMD gene

• Deficiency of dystrophin → progressive skeletal and cardiac muscle atrophy

• Most common muscular dystrophy, presenting in early childhood

• Markedly elevated CK due to muscle fibre degeneration

Patient Profile

• Typically affects boys aged 2–3 years (very rare in girls)

• Family history might indicate the need for genetic counselling

Presentation

• Delayed motor milestones (e.g. crawling instead of walking)

• Waddling gait, calf pseudohypertrophy (calf muscle replaced by fat/fibrosis)

• Hypotonia, hyporeflexia

• Mild-to-moderate intellectual impairment

• Positive Gower’s sign (child uses arms to “climb” up legs when standing)

• Progressive difficulty with running, jumping, climbing stairs

Diagnosis

• Genetic testing (mutation in DMD gene, elevated CK)

• Muscle biopsy (assessing dystrophin staining if genetic test inconclusive)

• Cardiac evaluation (ECG, echocardiogram) to monitor for cardiomyopathy

Treatment

• Neurology referral (specialist in neuromuscular disorders)

• Corticosteroids (prednisone or deflazacort) to slow progression and prolong ambulation

• Physiotherapy and occupational therapy for mobility maintenance and contracture prevention

• Cardiac medications and respiratory support as needed

• Genetic counselling for family planning and risk assessment

Complications

• Respiratory failure (due to diaphragmatic and intercostal muscle weakness)

• Cardiomyopathy and arrhythmias (potentially life-threatening)

• Scoliosis (may require surgical intervention)