Muscular dystrophy

• Childhood pseudohypertrophic muscular dystrophy
• Adult pseudohypertrophic muscular dystrophy
• Duchenne muscular dystrophy
• Becker’s muscular dystrophy
• Benign X-linked recessive muscular dystrophy

• 359.0 Congenital hereditary muscular dystrophy
• 359.1 Hereditary progressive muscular dystrophy

• G71.0 Muscular dystrophy
• G71.2 Congenital myopathies

• 5E: Impaired Motor Function and Sensory Integrity Associated with Progressive Disorders of the Central Nervous System

Description

• Group of genetic disorders that result in progressive muscle weakness due to loss of myofibrils
• Causes defects in muscle proteins: weakens the musculoskeletal system
• Muscle cell and tissue death

Essentials of Diagnosis

• Nine major types of muscular dystrophy
• Diagnosed through molecular characteristics
• Diagnosis is dependent on
  • Age of patient at onset of symptoms
  • Areas of body involved
  • Rate of progression of symptoms

General Considerations

• Duchenne MD (type I)
  • Symptoms begin around 3 to 5 years of age
  • Characterized by pseudohypertrophy of calves
  • Progresses quickly
• Becker’s MD (type II)
  • Symptoms begin around 11 years of age
  • Characterized by muscle weakness of shoulder girdle, trunk, and extremities
  • Progresses slowly
• Congenital muscular dystrophies
  • Congenital MD with central nervous system disease (Fukuyama syndrome, Walker-Warburg syndrome, muscle-eye-brain-disease)
  • Integrin-deficient congenital MD
  • Merosin-deficient congenital MD
  • Congenital MD with normal merosin
    • Symptoms begin at birth
    • Characterized by hypotonia and contractures at birth
    • Progresses slowly but varies
• Congenital myotonic MD
  • Symptoms begin at birth
  • Characterized by severe hypotonia and muscle weakness at birth
  • Progresses slowly
  • Cognitive impairment present
• Childhood-onset facioscapulohumeral MD
  • Symptoms begin by 2 to 10 years of age
  • Characterized by muscle weakness of face and shoulder girdle
  • Progresses slowly
  • Eventually becomes non-ambulatory
• Emery-Dreifuss (humeroperoneal) MD
  • Symptoms begin prior to teenage years
  • Characterized by contractures of posterior cervical muscles, biceps, and plantar flexors
  • Progresses slowly, but often cardiac involvement
• Limb-girdle MD
  • Symptoms begin during teen years to adulthood
  • Characterized by muscle weakness of the shoulder and pelvic girdles
  • Progresses slowly

Demographics

• Duchenne MD: 1:3500 males
• Becker’s MD: 1:20,000 births
• Congenital myotonic MD: 1:8000 births
• Childhood-onset facioscapulohumeral MD: 3 to 10 per 1,000,000 births
• Emery-Dreifuss MD: rare

Signs and Symptoms

• Fatigue
• Complaint of muscle cramps (Becker’s)
• Progressive weakness and atrophy of involved muscles
• Fasciculations (of tongue)
• Dysphagia
• Dysarthria
• Contractures at birth (congenital and congenital myotonic forms of MD)
• Scoliosis
• Cognitive impairment
• Learning disabilities (Duchenne and Becker’s)
• Waddling gait
• Inability to run
• Inability to jump
• Gower’s sign
• Difficulty stair climbing
• Toe walking
• Falls
• Decreased maximal vital capacity
• Scapular winging
• Clubfoot (talipes equinovarus)

Functional Implications

• Progressive dependence for assistance with activities of daily living
• Easily fatigued
• Loss of mobility

Possible Contributing Causes2,3

• Duchenne, Becker’s and Emery-Dreifuss MDs are X-linked recessive diseases resulting in an inability to use dystrophin that is important to the sarcolemma
• Congenital MD is autosomal ...