A possible association of hypokalaemic periodic paralysis, autoimmune thyroiditis and neuromyotonia.

Acute hypokalemic periodic paralysis (HPP), a clinical syndrome characterised by acute systemic weakness and low serum potassium (K+), is a rare but treatable cause of acute limb weakness. Hypokalemia can be caused by K+ loss via the kidneys or extra renal routes mainly the gut, or due to transcellular potassium shifts where extracellular K+ will move into the cell. In the latter situation, although there is hypokalaemia, there is no deficit of K+ in the body. The main causes for intracellular shift of K+ are familial hypokalemic periodic paralysis, thyrotoxic periodic paralysis, barium poisoning, insulin excess and alkalosis. Although the association between thyrotoxicosis and HPP is known, HPP with hypothyroidism is extremely rare. We report a case of hypokalemic periodic paralysis associated with hypothyroidism and neuromyotonia.