Hypokalemic Periodic Paralysis, Type 2

Disease characteristics. Hypokalemic periodic paralysis (HOKPP) is a condition in which affected individuals may experience paralytic episodes with concomitant hypokalemia (2.5 mmol/L), and occasionally may develop late-onset proximal myopathy. The paralytic attacks are characterized by reversible flaccid paralysis usually leading to paraparesis or tetraparesis but typically sparing the respiratory muscles and heart. Acute paralytic crises usually last at least several hours and sometimes days. Some individuals have only one episode in a lifetime; more commonly, crises occur repeatedly: daily, weekly, monthly, or less often. The major triggering factors are carbohydrate-rich meals and rest after exercise; rarely, cold-induced hypokalemic paralysis has been reported. The interval between crises may vary and may be prolonged by preventive treatment with potassium salts or acetazolamide. The age of onset of the first attack ranges from one to 20 years; the frequency of attacks is highest between ages 15 and 35 and then decreases with age. A variable myopathy develops in at least 25% of affected individuals and may result in a progressive fixed muscle weakness that manifests at variable ages as exercise intolerance predominantly in the lower limbs. It may occur independent of paralytic symptoms and may be the sole manifestation of HOKPP. Individuals with HOKPP are at increased risk for pre- or post-anesthetic weakness and may be at an increased risk for malignant hyperthermia – though not as great a risk as in individuals with true autosomal dominant malignant hyperthermia susceptibility (MHS)..................



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