Hypokalemic periodic paralysis

Hypokalemic periodic paralysis is a disorder marked by recurrent attacks of muscle weakness or paralysis associated with low blood potassium. Most cases arise from inherited ion-channel dysfunction that makes muscle fibers temporarily inexcitable.

CACNA1S: CACNA1S is the gene encoding the alpha-1 subunit of the skeletal-muscle L-type calcium channel. Variants in CACNA1S are a leading cause of inherited attacks.
Potassium: Potassium is an essential electrolyte that supports cellular electrical activity, muscle contraction, and nerve signaling. Its blood concentration falls during attacks, although total-body potassium is often not depleted.
Autosomal dominant inheritance: Autosomal dominant inheritance occurs when one altered gene copy on a non-sex chromosome can cause a trait or disorder. The classic inherited form often passes through families in this pattern.
Periodic paralysis: Periodic paralysis is a group of disorders causing recurrent, reversible episodes of skeletal-muscle weakness. This condition is the low-potassium-associated member of the group.
SCN4A: SCN4A is the gene encoding the principal voltage-gated sodium channel in skeletal muscle. Some disease-causing variants alter muscle excitability through this sodium channel.
Hypokalemia: Hypokalemia is a lower-than-normal concentration of potassium in the blood. It is the defining laboratory abnormality during many attacks, but does not alone identify their cause.
CACNA1S-related hypokalemic periodic paralysis: CACNA1S-related hypokalemic periodic paralysis is an inherited form caused by pathogenic variants in CACNA1S. It accounts for a substantial share of genetically confirmed cases.
Hyperkalemic periodic paralysis: Hyperkalemic periodic paralysis is an inherited disorder causing episodic muscle weakness associated with normal or elevated blood potassium. It produces similar episodic weakness but differs in potassium pattern and typical attack triggers.
Kir2.1: Kir2.1 is an inwardly rectifying potassium channel encoded by KCNJ2 that helps stabilize muscle-cell membrane voltage. Channel dysfunction can produce a related periodic paralysis with additional cardiac and developmental features.
Electromyography: Electromyography records electrical activity in skeletal muscles using surface or needle electrodes. Long-exercise testing can reveal characteristic muscle electrical changes between attacks.

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Muscle weaknessBroader topic: It shows that changes in electrolyte balance can trigger attacks of weakness.