Neuromuscular Diseases

Question 1

Myastenic Crisis:

Precipitating factors

Answer 1

• Infection or surgery
• Pregnancy or. childbirth
• Tapering immunosuppressive drugs
• Meds:
  
  • Abx (aminoglycosides and tetracyclines)
  • Beta-blockers
  • Antiarrhythmics–quinidine, procainamide, lidocaine

Question 2

X-linked recessive (almost exclusively in males) disease involving mutation on a gene that codes for the dystrophin protein (dystrophin is absent causing muscles to die)

Characteristically, there is NO inflammation

Answer 2

Duchenne Muscular Dystrophy

Question 3

DMD:

Clinical Features

Answer 3

• Muscle weakness: progressive, symmetric, starts in childhood
  
  • Proximal muscles primarily affected (pelvic girdle)
  • Eventually involves respiratory muscles
• Gowers maneuver
• Enlarged calf muscles–true muscle hypertrophy at first, followed by pseudohypertrophy as fat replaces muscle
• Ultimately. results in wheelchair confinement, respiratory failure, and death in 3rd decade

Question 4

DMD:

Dx & Tx

Answer 4

Dx: Serum CPK high / DNA testing (has now replaced muscle biopsy)

Tx: Prednisone / Surgery to correct scoliosis

Question 5

Becker MD

Inheritance?

Difference?

Answer 5

XLR

Similar to DMD, but there is later onset and a less severe course. Some dystrophin present.

Question 6

Hereditary Causes of Muscle Weakness

Answer 6

• Mitochondrial disorders:
  
  • Associated with maternal inheritance and ragged red muscle fibers
• Glycogen storage disease (i.e., McArdle Disease)
  
  • AR
  • Muscle cramping after exercise due to glycogen phosphorylase deficiency