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

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

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

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Description

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  • 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

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Essentials of Diagnosis

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  • 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

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General Considerations

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  • 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

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Demographics

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  • 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

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Signs and Symptoms

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  • 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)

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Functional Implications

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

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Possible Contributing Causes2,3

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  • 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 recessive on chromosome 6q22
  • Congenital myotonic MD ...

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