Muscular Dystrophies

Duchenne Muscular Dystrophy

Definition

• Progressive muscle weakness in young boys
• X-linked recessive

Clinical Features

• Clumsy walking
• Reduced motor skills
• Pseudohypertrophy of the calf (classic) – connective tissue infiltration
• Scoliosis
• Respiratory difficulty in advanced stages
• Gower’s sign:
  • Rises by walking hands up thighs to compensate for quadriceps and gluteal weakness
  • First affected area is gluteals

Diagnosis

• DNA Testing: Absent Dystrophin protein
• High Creatine Phosphokinase (CPK)
• Muscle Biopsy:
  • Absent Dystrophin (diagnostic)
  • Connective tissue infiltration and muscle necrosis

Management

Non-Surgical

• Physical Therapy (PT), Occupational Therapy (OT)
• High-dose steroids:
  • Prolong ambulation
  • Slow scoliosis progression
• Complications:
  • Overnight ventilatory support

Surgical

• Controversial due to:
  • High anesthetic risks
  • Questionable benefit
  • Malignant Hyperthermia – intra-operative dantrolene
• Specific Procedures:
  • Release of knee contractures: May prolong ambulation by 1–2 years
  • Scoliosis:
    • Rapid progression as muscles weaken
    • Long fusion recommended at >20° curvature to address thoracic compromise

Outcomes

• Unable to walk independently by 10 years
• Wheelchair-bound by 14 years
• Bedridden by 16 years
• Death by cardiopulmonary compromise by 20 years

Becker’s Muscular Dystrophy

Characteristics

• X-linked recessive
• Associated with red/green color blindness

Clinical Features

• Similar to Duchenne but less severe

Diagnosis

• Muscle Biopsy:
  • Reduced but not absent Dystrophin

Outcomes

• Survival beyond 22 years is indicative of Becker’s Muscular Dystrophy

Facioscapulohumeral Dystrophy

Characteristics

• Autosomal dominant

Clinical Features

• Facial muscle abnormalities
• Shoulder girdle weakness
• Normal Creatine Phosphokinase (CPK)
• Bilateral scapula winging

Management

• Scapulothoracic Fusion: For symptomatic cases