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Alternative names Return to top
Paramyotonia congenita; Periodic paralysis - hyperkalemicDefinition Return to top
Hyperkalemic periodic paralysis is associated with elevated levels of potassium in the bloodstream. The disorder causes occasional episodes of muscle weakness.Causes, incidence, and risk factors Return to top
The cause of hyperkalemic periodic paralysis is believed to be a genetic muscle disease. In most cases it is inherited directly; 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 not uncommon.
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 triggerd by cold expsoure or 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. (It 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 that are capable of carrying an electrical current, such as sodium and potassium.)
Weakness most commonly affects the muscles of the arms and legs. Heart arrhythmias may occasionally develop during attacks. Although muscle strength is initially normal between attacks, repeated attacks may eventually cause progressive and persistent muscle weakness between attacks.
Risks include a family history of periodic paralysis. Attacks may be triggered by fasting. Attacks seldom occur during exercise but may be triggered by rest following exercise.
Disorders that cause intermittent episodes of paralysis as their primary effect are uncommon. More commonly, an intermittent episode of paralysis or weakness is a symptom of another disorder.
Hyperkalemic periodic paralysis occurs in approximately 1 in every 100,000 people. Men are affected more often than women and usually have more severe symptoms.
Symptoms Return to top
Signs and tests Return to top
The health care provider may suspect hyperkalemic periodic paralysis based on other family members having the disorder, symptoms that come and go, normal or high results of a potassium test, and ruling out other disorders as the cause of intermittent weakness.
Between attacks, examination is normal. During an attack, the following may be observed:
Attacks are not triggered by tests that reduce serum potassium (such as giving insulin and glucose) but may be triggered by giving potassium. Serum potassium is normal or high during attacks and may be normal or high between attacks.
Treatment Return to top
The goals of treatment are relief of acute symptoms and prevention of further attacks.Expectations (prognosis) Return to top
Sometimes attacks resolve later in life on their own. However, chronic attacks generally result in progressive muscle weakness that is present even between attacks.
Hyperkalemic periodic paralysis responds well to treatment. Treatment may prevent, and may even reverse, progressive muscle weakness.
Complications Return to top
Calling your health care provider Return to top
Call your health care provider if intermittent muscle weakness occurs, particularly if there is a family history of periodic paralysis.Prevention Return to top
Treatment prevents attacks of weakness. Update Date: 8/5/2004 Updated by: Ari Mosenkis, M.D., Department of Nephrology, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.
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Page last updated: 28 October 2004 |