Periodic Paralysis

Periodic Paralysis is a topic covered in the 5-Minute Emergency Consult.

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Basics

Description

  • Periodic paralysis (PP): Disorder of muscle metabolism usually inherited that leads to flaccid extremity weakness. Exacerbated by hyperkalemia, hypokalemia, thyrotoxicosis
  • Primary: Familial AD mutation skeletal muscle calcium, sodium, or potassium channel
  • Secondary: Thyrotoxic, hypokalemia, hyperkalemia

Epidemiology

Incidence and Prevalence Estimates
  • Hypokalemic PP (HypoPP):
    • MC, 1:100,000 prevalence
    • 1/3 new AD mutations
  • Hyperkalemic PP (HyperPP):
    • 1:200,000 prevalence
    • 90% of people with mutation will have clinical symptoms
  • Thyrotoxic PP (ThyroPP):
    • Incidence 2% in patients with thyrotoxicosis
    • Higher in Asians
    • Subset of HypoPP, clinically identical
  • Andersen–Tawil:
    • Subset of HypoPP
    • Rare
    • Prevalence unknown

Etiology

  • Mutation of skeletal muscle Na channel gene:
    • SCN4A
    • HypoPP, HyperPP:
      • AD inheritance
      • Spontaneous mutation
  • Mutation of skeletal muscle calcium channel gene CACN1AS:
    • HypoPP
  • Mutation of KCNJ2 gene:
    • Andersen–Tawil:
      • AD inheritance
      • 50% spontaneous
  • M>F
  • Age of onset:
    • HypoPP:
      • 1st or 2nd decade
    • HyperPP:
      • 1st decade
    • Andersen–Tawil:
      • 1st or 2nd decade
    • ThyroPP:
      • 2nd–5th decade

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