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Familial Periodic Paralysis
Aka: Familial Periodic Paralysis, Hypokalemic Periodic Paralysis
- See Also
- Serum Potassium
- Hypokalemia Approach
- Hypokalemia due to Renal Potassium Loss
- Hypokalemia due to Extrarenal Potassium Loss
- Hypokalemia due to Transcellular Potassium Shift
- Familial Periodic Paralysis
- Potassium Replacement
- Dietary Potassium
- Epidemiology
- Prevalence: 1 in 100,000 (rare)
- Typical onset of symptoms before age 20 years
- More common in males
- Causes
- Genetic
- Autosomal Dominant disorder of Hypokalemia
- Most often related to a Sodium channel disorder, with a shifting of Potassium into tissues
- Acquired
- Hyperthyroidism
- Risk Factors: Triggers
- Alcohol Abuse
- Corticosteroid use
- Insulin
- Renal disease
- Large Carbohydrate containing meals
- High salt intake
- Intense Exercise
- Glue sniffing
- Prolonged immobility
- Cold Weather
- Anesthetics
- Symptoms
- Headaches
- Thirst
- Lethargy
- No associated pain
- Signs
- Slow progressive weakness (especially following triggers)
- Weakness lasts for hours to days
- Episodic muscular paralysis (lower extremities > upper extremities)
- Shoulder
- Pelvic girdle
- Other areas follow
- Muscle Strength normal between attacks
- Deep Tendon Reflexes
- Diminished or absent
- Associated Conditions
- Thyrotoxicosis
- Especially in young asian males, with onset after Exercise
- Labs
- Consider extending evaluation to cover differential diagnosis as below
- Serum Electrolytes including Renal Function and Magnesium
- Serum Potassium with Hypokalemia during episode (normal between episodes)
- Hypomagnesemia may be associated with other causes of Hypokalemia
- Thyroid Stimulating Hormone (TSH)
- Evaluate for Thyrotoxicosis
- Genetic Testing
- Genetic outpatient testing if findings consistent with familial Hypokalemia
- Diagnostics
- Electrocardiogram
- See Hypokalemia for related EKG changes
- Differential Diagnosis
- See Hypokalemia Causes
- See Acute Motor Weakness Causes
- Management
- Replace Potassium IV in severe cases (oral Potassium in mild cases)
- See Potassium Replacement
- Exercise caution with replacement (risk of overshooting as Muscles release Potassium on recovery)
- Replace Magnesium if low
- Avoid high Carbohydrate intake
- Avoid Excessive Salt Intake
- Complications
- Myopathy
- Prevention
- Carbonic anhydrase inhibitors (e.g. Acetazolamide)
- Potassium sparing Diuretics (e.g. Spironolactone)
- References
- Candy and Herbert in Herbert (2020) EM:Rap 20(11): 8-9
- Claudius and Behar in Herbert (2019) EM:Rap 19(11):12-3