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Hyperkalemic periodic paralysis

Definition

Hyperkalemic periodic paralysis is a disorder that causes occasional episodes of muscle weakness and sometimes a higher than normal level of potassium in the blood.

It is one of a group of genetic disorders that includes hypokalemic periodic paralysis and thyrotoxic periodic paralysis.

Alternative Names

Periodic paralysis - hyperkalemic

Causes

Hyperkalemic periodic paralysis is congenital. This means it is present at birth. In most cases, it is passed down through families (inherited) as an autosomal dominant disorder. In other words, only one parent needs to pass the gene related to this condition on to you in order for you to be affected.

Occasionally, the condition may be the result of a genetic problem that is not inherited.

It is believed that the disorder is related to problems with the way the body controls sodium and potassium levels in cells.

Risk factors include having other family members with periodic paralysis. It affects men more often than women.

Symptoms

Symptoms include attacks of muscle weakness or loss of muscle movement (paralysis) that come and go. There is normal muscle strength between attacks.

Attacks usually begin in childhood. How often the attacks occur varies. Some people have several attacks a day. Attacks typically last only 1 to 2 hours, but can sometimes last as long as a day. They are usually not severe enough to need therapy. Some people have associated myotonia, in which they cannot immediately relax their muscles after use.

The weakness or paralysis:

  • Most commonly occurs at the shoulders and hips
  • May also involve the arms and legs, but does not affect muscles of the eyes and muscles that help with breathing and swallowing
  • Most commonly occurs while resting after activity or exercise
  • May occur on awakening
  • Occurs on and off
  • Usually lasts 1 to 2 hours

Triggers may include:

  • Eating a high carbohydrate meal
  • Exercise
  • Exposure to cold
  • Eating potassium-rich foods or taking medicines that contain potassium

Exams and Tests

The health care provider may suspect hyperkalemic periodic paralysis based on a family history of the disorder. Other clues to the disorder are muscle weakness symptoms that come and go with normal or high results of a potassium test.

Between attacks, a physical examination shows nothing abnormal. During and between attacks, potassium blood level can be normal or high.

During an attack, muscle reflexes are decreased or absent. And muscles go limp rather than staying stiff. Muscle groups near the body, such as the shoulders and hips, are involved more often than the arms and legs.

Tests that may be done include:

  • ECG, which may be abnormal during attacks
  • EMG, which is usually normal between attacks and abnormal during attacks
  • Muscle biopsy, which may show abnormalities

Other tests may be ordered to rule out other causes.

Treatment

The goal of treatment is to relieve symptoms and prevent further attacks.

Attacks are seldom severe enough to require emergency treatment. But weakness can become worse with repeated attacks. So treatment to prevent the attacks should occur as soon as possible.

Glucose or other carbohydrates (sugars) given during an attack may reduce the severity of the symptoms. Calcium or diuretics (water pills) may need to be given through a vein to stop sudden attacks.

Outlook (Prognosis)

Sometimes, attacks disappear later in life on their own. But repeated attacks may lead to permanent muscle weakness.

Hyperkalemic periodic paralysis responds well to treatment. Treatment may prevent, and may even reverse, progressive muscle weakness.

Possible Complications

  • Kidney stones (a side effect of medicine used to treat the condition)
  • Irregular heart beat
  • Difficulty breathing, speaking, or swallowing during attacks (rare)
  • Muscle weakness that slowly continues to get worse

When to Contact a Medical Professional

Call your health care provider if you have muscle weakness that comes and goes, especially you have family members who have periodic paralysis.

Go to the emergency room or call the local emergency number (such as 911) if you faint or have difficulty breathing, speaking, or swallowing.

Prevention

A medicine called acetazolamide prevents attacks in many cases. Other medicines may also be prescribed. A low potassium, high carbohydrate diet may help prevent attacks. Avoiding fasting, strenuous activity, or cold temperatures also may help.

References

Chinnery PF. Muscle diseases. In: Goldman L, Schafer AI, eds. Goldman’s Cecil Medicine. 24th ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 429.

Mount DB, Zandi-Nejad K. Disorders of potassium balance. In Taal MW, Chertow GM, Marsden PA, et al., eds. Brenner and Rector’s The Kidney. 9th ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 17.


Review Date: 11/7/2013
Reviewed By: Brent Wisse, MD, Associate Professor of Medicine, Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and /the A.D.A.M. Editorial team. 11/07/13
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