Paramyotonia congenita (PMC) is a muscle disorder which causes muscle stiffness (myotonia) that appears during exercise and becomes much more severe upon exposure to cold. The myotonia which occurs during attacks of PMC may be so severe that the patient cannot inhale and exhale properly, and movement becomes difficult. The medical term myotonia means that the muscle fibers are slow to relax after contraction.
Hyperkalemic Periodic Paralysis (HyperKPP) is a rare inherited muscle disorder which causes episodes of paralysis or weakness. It's estimated to occur in only one of 250,000 individuals, though since it is inherited there may be several patients in a single family. It was only recognized as a separate disorder in 1955.
The periodic paralyses are a group of rare inherited disorders that cause temporary episodes of muscle weakness or paralysis. Periodic Paralysis is found in all races and in both sexes. Some patients have their first attack within minutes of birth, but a few don't have symptoms until they are in their 60’s or 70’s. Attacks can last only a few moments or go on for days, depending on the type of periodic paralysis the person has. Some forms of periodic paralysis include muscle stiffness or rigidity as part of the attacks.
The information on this site is based on current medical knowledge but should never at any time be substituted for the advice and care of a properly qualified medical consultant. For medical advice seek the services of a physician.