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Hypokalaemic Periodic Paralysis — SCE Neurology MCQ

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HardPeripheral Neuropathy & NeuromuscularHypokalaemic Periodic ParalysisSCE Neurology

A 25-year-old man presents with recurrent episodes of flaccid paralysis lasting hours to days, triggered by rest after strenuous exercise or carbohydrate-rich meals. During an attack his serum potassium is 2.8 mmol/L. Between attacks his examination is normal. His father has similar episodes. Genetic testing confirms a mutation in the CACNA1S gene. What is the diagnosis?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: D — Hypokalaemic periodic paralysis

Hypokalaemic periodic paralysis is an autosomal dominant channelopathy (most commonly CACNA1S mutations — calcium channel; or SCN4A — sodium channel) causing episodic flaccid paralysis with low serum potassium during attacks. Triggers include rest after exercise, high-carbohydrate meals, stress, and cold. Treatment includes potassium supplementation during attacks, acetazolamide for prevention, and avoidance of triggers. A: MG has fatigable weakness, not episodic paralysis. C: Hyperkalaemic PP has elevated potassium during attacks. D: Andersen-Tawil has periodic paralysis + cardiac arrhythmias + dysmorphic features. E: GBS is monophasic.

Reference: EAN Periodic Paralysis Guidelines; ABN Channelopathy Guidelines