[Tubolopaties associated to hypokalemia]

We have described two clinical cases of two young men affected by hypkalemia associated with metabolic alkalosis. The first patient also presented hypercalciucia, normal magnesemia, defect in renal concentrating ability and increased renin activity; in addition he was affected by congenital sensorineural deafness. The diagnosis of Bartter's syndrome was made and it was confirmed by the gene analysis, which revealed a mutation for the beta-subunit of the ClC chloride channels known as barttin. The second case was characterized by hypocalciuria and hypomagnesemia, polyuria and nicturia. The genetic analysis revealed a mutation for the gene encoding the Na+-Cl(-) cotransporter and the diagnosis of Gitelman's syndrome was formulated. We present experimental and clinical evidence to explain, at the molecular level, the differences in calcium and magnesium homeostatis in the two cases. Moreover, we propose different causes to justify the pathogenesis of hypokalemia and the related metabolic alkalosis.