A group of diseases with diverse etiologies to included familial (hereditary), thyrotoxicosis, barium poisoning, renal tubular acidosis, primary hyperaldosteronism, licorice ingestion and gastrointestinal potassium losses. The diseases manifest as acute muscular weakness which is intermittent and usually resolves after 36 hours or less. Three different varieties of this disease are present: hyperkalemic, normokalemic and hypokalemic. The weakness is usually limited to the limb and limb girdles; however, rarely, the cranial and bulbar musculature may be affected, and deaths from respiratory failure and cardiac arrhythmias have been reported. Histologically, the presence of vacuoles in otherwise healthy muscle cells is diagnostic of the hypokalemic variety.
Caucasians are typically affected with the familial variety; whereas, thyrotoxic periodic paralysis is most prevalent in Asians. Familial hypokalemic periodic paralysis displays an autosomally dominant inheritance pattern. The pathogenesis of the familial form is incompletely understood, but an abnormality of muscle cell membranes is believed to be involved. Thyrotoxic hypokalemic periodic paralysis resolves with appropriate management of thyrotoxicosis. Hyperkalemic periodic paralysis is misleading as the potassium level in these patients is usually elevated normally but decreases to normal levels during attacks. In the hyperkalemic variety, attacks are usually precipitated by potassium administration
The therapy for severe acute attacks of hypokalemic periodic paralysis entails oral potassium chloride (0. 2 - 0.4 mmol/kg every 15 - 30 minutes). Intravenous potassium chloride (0.1 mmol/kg over 5 to 10 minutes) may be used in patients who cannot tolerate oral therapy. An electrocardiogram should be used to monitor cardiac response to potassium levels. Potassium chloride is an ineffective choice as a prophylactic agent. Rather, acetazolamide (125 - 250 mg PO either BID or QID) is an effective prophylactic.
Acute attacks of hyperkalemic periodic paralysis are usually mild and do not warrant therapy. When prophylaxis is necessary, acetazolamide (125 - 250 mg PO either BID or QID) or chlorothiazide (250 - 1000 mg/day) are effective options.