[Gitelman syndrome: a crucial role of laboratory medicine for the diagnosis].

We described a case of Gitelman syndrome. A 56-year-old healthy man presented with facial paralysis. Initial laboratory tests revealed hypokalemia. Despite potassium supplements, kaliemia remains at low levels. Further investigations showed urinary potassium wasting, hypomagnesemia and hypocalciuria. Diagnosis of Gitelman syndrome has been confirmed by molecular diagnosis with identification of a composite heterozygote mutation on SLC12A3 gene. One of the mutations on exon 1 SCL12A3 gene wasn't yet known. In the patient family, the same genetic disorder has been found in the sister. Treatment and follow up schedule were proposed to patient.