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HEREDITARY MONOGENIC DISEASES

           

Hypokalemic periodic paralysis

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

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 the teen years, but they can occur before age 10. How often the attacks occur varies. Some people have attacks every day. Others have them once a year. During attacks the person remains alert.

The weakness or paralysis:

  • Most commonly occurs at the shoulders and hips
  • May also affect the arms, legs, muscles of the eyes, and muscles that help with breathing and swallowing
  • Occurs off and on
  • Most commonly occurs on awakening or after sleep or rest
  • Is rare during exercise, but may be triggered by resting after exercise
  • May be triggered by high-carbohydrate, high-salt meals or drinking alcohol
  • Usually lasts 3 to 24 hours

Other symptoms may include:

  • Eyelid myotonia (a condition in which after opening and closing the eyes, they cannot be opened for a short time).

CAUSES AND RISK FACTORS

Hypokalemic 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.

Unlike other forms of periodic paralysis, persons with congenital hypokalemic periodic paralysis have normal thyroid function. But they have a very low blood level of potassium during episodes of weakness. This results from potassium moving from the blood into muscle cells in an abnormal way.

Risk factors include having other family members with periodic paralysis. The risk is slightly higher in Asian men who also have thyroid disorders.

PREVENTION

Hypokalemic periodic paralysis cannot be prevented. Because it can be inherited, genetic counseling may be advised for couples at risk of the disorder.

Treatment prevents attacks of weakness. Before an attack, there may be leg stiffness or heaviness in the legs. Doing mild exercise when these symptoms start may help prevent a full-blown attack.

GENE OR REGION STUDIED


  • CACNA15
  • SCN4A