Potassium

Familial Periodic Paralysis

search

Familial Periodic Paralysis, Hypokalemic Periodic Paralysis

  • Epidemiology
  1. Typical onset of symptoms before age 20 years
  2. More common in males
  • Pathophysiology
  1. Autosomal Dominant disorder of Hypokalemia
  2. Most often related to a Sodium channel disorder, with a shifting of Potassium into tissues
  • Risk Factors
  • Triggers
  1. Alcohol Abuse
  2. Corticosteroid use
  3. Renal disease
  4. Large carbohydrate containing meals
  5. Intense Exercise
  6. Glue sniffing
  • Symptoms
  1. Headaches
  2. Thirst
  3. Lethargy
  4. No associated pain
  • Signs
  1. Slow progressive weakness (especially following triggers)
    1. Weakness lasts for hours to days
  2. Episodic muscular paralysis (lower extremities > upper extremities)
    1. Shoulder
    2. Pelvic girdle
    3. Other areas follow
  3. Muscle Strength normal between attacks
  4. Deep Tendon Reflexes
    1. Diminished or absent
  • Associated Conditions
  1. Thyrotoxicosis
    1. Especially in young asian males, with onset after Exercise
  • Labs
  1. Consider extending evaluation to cover differential diagnosis as below
  2. Serum electrolytes including Renal Function and Magnesium
    1. Serum Potassium with Hypokalemia during episode (normal between episodes)
    2. Hypomagnesemia may be associated with other causes of Hypokalemia
  3. Thyroid Stimulating Hormone (TSH)
    1. Evaluate for Thyrotoxicosis
  4. Genetic Testing
    1. Genetic outpatient testing if findings consistent with familial Hypokalemia
  • Diagnostics
  1. Electrocardiogram
    1. See Hypokalemia for related EKG changes
  • Differential Diagnosis
  • Management
  1. Replace Potassium IV
    1. See Potassium Replacement
    2. Exercise caution with replacement (risk of overshooting as muscles release Potassium on recovery)
  2. Avoid high carbohydrate intake
  3. Avoid excessive salt intake
  • References
  1. Claudius and Behar in Herbert (2019) EM:Rap 19(11):12-3