A novel compound heterozygous mutation of Gitelman's syndrome in Japan, as diagnosed by an extraordinary response of the fractional excretion rate of chloride in the trichlormethiazide loading test.

Gitelman's syndrome (GS), an inherited disorder due to loss of function of ion channels and transporters such as Na-Cl co-transporter (NCCT) in distal convoluted tubules, is characterized by hypokalemia, hypomagnesemia, hypocalciuria, metabolic alkalosis and hyperreninemic-hyperaldosteronism. A 39-year-old man was admitted to our hospital because of muscle weakness with such intractable disorders. We performed a thiazide-loading test, which revealed a poor response of the fractional excretion rate of chloride compared to healthy subjects. Based on these data, the clinical diagnosis of GS was made. Gene-sequencing analysis revealed compound heterozygous mutations of c.539C > A and c.1844C > T in SLC12A3, which is newly reported in Japanese GS.