Hyperkalemic periodic paralysis

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Muscular atrophy

Hyperkalemic periodic paralysis is associated with elevated levels of potassium in the bloodstream. The disorder causes occasional episodes of muscle weakness.

Paramyotonia congenita; Periodic paralysis - hyperkalemic

The cause of hyperkalemic periodic paralysis is believed to be a genetic muscle disease. In most cases it is inherited directly (from parent to child); in other cases, it occurs randomly in a family group.

The disorder involves attacks of muscle weakness or paralysis, alternating with periods of normal muscle function. Attacks usually begin in early childhood. Multiple daily attacks are possible.

Attacks typically last only 1 to 2 hours, but can sometimes last as long as a day. They tend to occur while resting after exercise or exertion. Attacks may also be triggered by exposure to cold, or by eating small amounts of potassium.

Unlike other forms of periodic paralysis (such as familial periodic paralysis and thyrotoxic periodic paralysis), hyperkalemic periodic paralysis is not associated with low potassium in the bloodstream (serum potassium). In fact, there may be normal or high levels of potassium in the bloodstream during and between attacks. The condition may be termed "normokalemic periodic paralysis" if potassium is normal during attacks.

Glucose and insulin administration, which trigger attacks of other forms of periodic paralysis, do not trigger attacks of hyperkalemic periodic paralysis. Giving potassium, which is used to treat weakness associated with the other disorders, worsens the weakness in this case.

The serum potassium levels are usually not at the level that would be expected to cause paralysis. The potassium level may remain normal or only very slightly elevated. It is thought that the disorder is caused by problems with the muscle cell wall and the way the body controls electrolyte levels in the cell (electrolytes are molecules, such as sodium and potassium, that are capable of carrying an electrical current.