Periodic paralyses: a group of diseases characterized by episodes of muscle weakness or paralysis that occur at irregular intervals. Most of these conditions are inherited (hereditary). The primary periodic paralyses are inherited diseases that are due to defective ion channels on body cells and are typically associated with abnormal potassium levels. Symptoms and signs depend upon the exact type of periodic paralysis that is present. In some cases the episodes of paralysis begin immediately after birth, while other affected people may not show symptoms until old age. The length of the paralysis episodes also varies according to the specific disease type. Some forms of periodic paralysis can lead to additional symptoms including muscle stiffness, muscle rigidity, or muscle shrinkage and wasting.
Types of periodic paralysis include Hypokalemic Periodic Paralysis, Thyrotoxic Periodic Paralysis, Hyperkalemic Periodic Paralysis, Paramyotonia Congenita von Eulenburg, the Potassium Aggravated Myotonias, and Andersen-Tawil Syndrome.