DescriptionHypokalemic periodic paralysis is a condition that causes episodes of extreme muscle weakness typically beginning in childhood or adolescence. Most often, these episodes involve a temporary inability to move muscles in the arms and legs. Attacks cause severe weakness or paralysis that usually lasts from hours to days. Some people may have episodes almost every day, while others experience them weekly, monthly, or only rarely. Attacks can occur without warning or can be triggered by factors such as rest after exercise, a viral illness, or certain medications. Often, a large, carbohydrate-rich meal or vigorous exercise in the evening can trigger an attack upon waking the following morning. Although affected individuals usually regain their muscle strength between attacks, some develop persistent muscle weakness later in life. Show People with hypokalemic periodic paralysis typically have reduced levels of potassium in their blood (hypokalemia) during episodes of muscle weakness. Researchers are investigating how low potassium levels may be related to the muscle abnormalities in this condition. FrequencyAlthough its exact prevalence is unknown, hypokalemic periodic paralysis is estimated to affect 1 in 100,000 people. Men tend to experience symptoms of this condition more often than women. CausesMutations in the CACNA1S or SCN4A gene can cause hypokalemic periodic paralysis. These genes provide instructions for making proteins that play essential roles in muscles used for movement (skeletal muscles). For the body to move normally, skeletal muscles must tense (contract) and relax in a coordinated way. Muscle contractions are triggered by the flow of certain positively charged atoms (ions) into muscle cells. The CACNA1S and SCN4A proteins form channels that control the flow of these ions. The channel formed by the CACNA1S protein transports calcium ions into cells, while the channel formed by the SCN4A protein transports sodium ions. Mutations in the CACNA1S or SCN4A gene alter the usual structure and function of calcium or sodium channels. The altered channels are "leaky," allowing ions to flow slowly but continually into muscle cells, which reduces the ability of skeletal muscles to contract. Because muscle contraction is needed for movement, a disruption in normal ion transport leads to episodes of severe muscle weakness or paralysis. A small percentage of people with the characteristic features of hypokalemic periodic paralysis do not have identified mutations in the CACNA1S or SCN4A gene. In these cases, the cause of the condition is unknown. InheritanceThis condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. Other Names for This Condition
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At what serum level does hypokalemia occur?Hypokalemia is generally defined as a serum potassium level of less than 3.5 mEq/L (3.5 mmol/L). Moderate hypokalemia is a serum level of 2.5-3.0 mEq/L, and severe hypokalemia is a level of less than 2.5 mEq/L. Hypokalemia is a potentially life-threatening imbalance that may be iatrogenically induced.
What condition is hypokalemia?Hypokalemia is a metabolic imbalance characterized by extremely low potassium levels in the blood. It is a symptom of another disease or condition, or a side effect of diuretic drugs.
What does hypokalemia mean?By Mayo Clinic Staff. Low potassium (hypokalemia) refers to a lower than normal potassium level in your bloodstream. Potassium helps carry electrical signals to cells in your body. It is critical to the proper functioning of nerve and muscles cells, particularly heart muscle cells.
What happens when serum potassium is low?A large drop in potassium level may lead to abnormal heart rhythms, especially in people with heart disease. This can cause you to feel lightheaded or faint. A very low potassium level can even cause your heart to stop.
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