Pathogenesis of sudden unexplained nocturnal death (lai tai) and endemic distal renal tubular acidosis.

Sudden unexplained nocturnal death (SUND), a disorder of unknown cause that occurs in otherwise healthy young adults, mostly male, during their sleep, is prevalent in the north-east region of Thailand, where it has been known for generations as lai tai. It occurs in the same population and area where hypokalaemic periodic paralysis (HPP), endemic distal renal tubular acidosis (EdRTA), and renal stones are also endemic. SUND has occurred in families of patients with EdRTA, and HPP can present as sudden onset of muscle parlysis with potentially lethal cardiac arrhythmias and respiratory failure from severe hypokalaemia occurring in the middle of the night. Surveys in which serum and urinary potassium have been measured indicate a deficiency of the electrolyte in the population. Potassium deficiency is probably the prime factor responsible for SUND and HPP. Low urinary citrate concentrations and the high prevalence of acidification defects in the population indicate that potassium deficiency is also responsible for the prevalence of EdRTA and for renal stones.