Hypokalemic Periodic Paralysis Type 1

Abstract

Hypokalemic periodic paralysis is characterized by episodes of muscle paralysis lasting from a few to 48 h, associated with a decrease in serum potassium levels, in the absence of myotonia. The paralytic attacks, which usually affect the four limbs (tetraplegia), are usually triggered by ingestion of meals rich in carbohydrates and by rest after exercise or stress. The onset of the disease usually occurs during the second decade of life, and attack frequency decreases with age. In some cases, there may be a vacuolar myopathy in muscle, resulting in permanent muscle weakness, and it is not clear how these vacuoles are related to paralytic attacks or muscle degeneration. The disease presents genetic heterogeneity (Table 43.1): about 70 % of cases are due to mutations in the CACNA1S gene encoding muscle calcium channel gene, whereas 10 % of cases are due to mutations in the SCN4A gene encoding muscle sodium channel.