Genetic renal disorders with hypomagnesemia and hypocalciuria.

The combination of hypomagnesemia and hypocalciuria is the phenotypic signature of two distinct genetic renal tubular transport disorders: Gitelman's syndrome and autosomal dominant isolated renal magnesium wasting. In the past 5 years the genetic defects underlying these disorders have been elucidated through positional candidate cloning approaches. The defective proteins involved in both diseases are located within the distal convoluted tubule (DCT), a segment of the nephron known to play an important role in active magnesium reabsorption in the nephron. The introduction outlines the magnesium handling in the body in general and, in particular, in the kidney, followed by a detailed discussion of Gitelman's syndrome and isolated renal magnesium wasting, including the clinical and biochemical symptoms, genetic aspects and pathophysiology.