Gitelman's syndrome (familial hypokalemia-hypomagnesemia).

Gitelman's syndrome (GS) is a heritable renal disorder characterized by hypomagnesemia, hypokalemia and hypocalciuria, and is distinct from Bartter's syndrome (BS). As compared to those with BS, patients with GS present at an older age, and they have a milder clinical picture, normal or slightly decreased concentrating urine ability, reduced urinary excretion of calcium, and permanently decreased serum magnesium level. GS is caused by defective NaCl transport in the distal convoluted tubule, and is linked to the gene encoding the thiazide sensitive Na-Cl-cotransporter located on chromosome 16q. Patients with BS, on the other hand, have mutations in the transporters in the thick ascending loop of Henle (NKCC2, ROMK, and C1C-Kb). Treatment of GS consists of magnesium salt replacement. Long term prognosis in terms of maintaining growth, preserving renal function and life expectancy is excellent.