Patients with hypokalemic periodic paralysis have periods of muscle weakness. In some cases, a patient can have severe paralysis. A genetic disorder, hypokalemic periodic paralysis is autosomal dominant, meaning that for a child to have the disorder, only one of her parents needs to pass on the gene.
While the exact number of patients with hypokalemic periodic paralysis is not known, Genetics Home Reference from the U.S. National Library of Medicine estimated that it affects 1 in 100,000 people.
The disorder results from mutations of two genes: CACNA1S and SCN4A. These genes provide the body with the instruction to produce proteins involved in controlling the flow of ions that help skeletal muscles contract and relax. The mutations affect the skeletal muscles’ ability to contract, leading to the episodes of muscle weakness or paralysis.
Some groups of patients with hypokalemic periodic paralysis may not have mutations of these two genes.