Myopathy

Question 1

Features of myotonic dystrophy

Answer 1

• myotonia is delayed relaxation after sustained muscle contraction- identified clinically and on electromyography
• autosomal dominant inheritence
• nucelotide triplet repeat expansion
• newborns:
  
  • ​hypotonia
  • poor feeding
  • respiratory difficulties
• older children
  
  • ​slow release of handshake
  • difficulty releasing tightly clasped fist
  • myopathic facies
  • learning difficulties
  • myotonia
• adults
  
  • ​cataracts
  • males: baldness, testicular atrophy
• death due to cardiomyopathy

Question 2

Features of DMD and CMD

Answer 2

• Duchenne’s muscular dystrophy
  
  • ​X-linked recessive disorder
  • site codes for protein: dystrophin
  • raised CPK
  • waddling gait
  • language delay
  • mount stairs one by one
  • run slowly vs peers
  • Gower’s sign​
  • Pseudohypertrophy of the calves
  • no longer ambulant at 10-14 years
  • life expctancy reduced to late twenties
    
    • ​respiratory
    • cardiomyopathy
  • 1/3 = learning difficulties
  • scoliosis
• Congenital muscular dystrophies
  
  • ​recessive inheritence
  • mm biopsy shows: dysmorphic features (with reduction of laminin protein)
  • presents at birth with:
    
    • hypotonia
    • weakness
    • contractures
    • proximal weakness is slowly progressive
    • tedency to contracture = when the ability to walk is lost
  • learning difficulties- central nervous system involvement

Question 3

Treatment of Duchenne’s muscular dystrophy

Answer 3

• Exercises
  
  • ​maintain muscle power and mobility
  • delays onset of scoliosis
  • contractures helped with passive stretching and night splints
  • walking with orthoses
• Steroids
  
  • ​corticosteroids (oral prednisolone) 10 days each month to preserve mobility and prevent scoliosis
• Cardiac medications
• Nocturnal ventilation- overnight CPAP/ NIPPV
  
  • nocturnal hypoxia due to weakness in IC mm