Familial periodic paralysis is a condition that causes occasional bouts of muscle weakness. It is usually brought on by an abnormal level of potassium in the blood.

What is going on in the body?

Familial periodic paralysis is an inherited condition. The episodes usually begin during the teenage years. When the attack occurs, there may be an abnormally high or low level of potassium in the blood. The exact cause of this condition is not well understood.

What are the causes and risks of the condition?

Familial periodic paralysis is usually an inherited condition. It may also occur randomly within certain families. It occurs in about 1 in 100,000 people. It is more common in Asian people and those who also have thyroid disorders.

The episodes of weakness usually occur after sleep or rest and rarely occur during exercise. Factors that increase the risk of having an attack in affected people depend on the type of periodic paralysis a person has. The condition is often split into three categories, based on the potassium level in the blood during attacks:

In the low potassium form of this condition, eating a meal that is high in carbohydrates or sodium may cause an attack of paralysis. People with the normal and high potassium forms of this condition are often sensitive to potassium. If these people eat a meal high in potassium, they may have an attack.