Hyperkalemic periodic paralysis
Periodic paralysis is a rare neuromuscular disorder, related to a defect in muscle ion channels, characterized by episodes of painless muscle weakness, which may be precipitated by heavy exercise, fasting, or high-carbohydrate meals.
Periodic paralysis (PP) is classified as hypokalemic when episodes occur in association with low potassium blood levels or as hyperkalemic when episodes can be induced by elevated potassium. Most cases of periodic paralysis are hereditary, usually with an autosomal dominant inheritance pattern. Acquired cases of hypokalemic PP have been described in association with hyperthyroidism. The clinical features of these disorders are summarized in the Table.
Hypokalemic PP and the periodic paralysis associated with the Andersen syndrome will be reviewed here. Other causes of periodic paralysis are discussed separately. (See "Hyperkalemic periodic paralysis" and "Thyrotoxic periodic paralysis".)
Hypokalemic periodic paralysis (PP) is the most common of the periodic paralyses, but is still quite rare, with an estimated prevalence of 1 in 100,000 . Hypokalemic PP may be familial with autosomal dominant inheritance or may be acquired in patients with thyrotoxicosis. (See "Thyrotoxic periodic paralysis".)
Clinical penetrance is often incomplete, especially in women . The disorder is three to four times more commonly clinically expressed in men. Approximately one-third of cases represent new mutations .