Endocrine Abstracts

Introduction: Gitelman syndrome (GS) is autosomal recessive disorder, characterised by hypokalemia, hypomagnesemia, metabolic alkalosis and low urinary calcium excretion. We report a case with final diagnosis of GS using the DNA analysis, presented with severe hypokalemia but normomagnesemia.

Case report: A 47-year-old Japanese male presented to our hospital because of severe hypokalemia in the annual health check-up. Severe hypokalemia was pointed out in the previous check-up, but he was reluctant to be investigated. He was totally asymptomatic and had no history of muscle weakness, palpitation and syncope. He denied the use of any medication including laxative and diuretics. He was normotensive and no growth retardation. The laboratory test revealed that the serum potassium was 1.7 mEq/l but he had no hypomagnesemia. His 24 h-urinary calcium excretion, 75 mg/day, was not so impaired. We analysed his genetic mutation by direct DNA sequencing. As a result, he had two genetic mutations on SLC12A3 which encoded the thiazide-sensitive NaCl cotransporter. These genetic mutations are found in the majority of GS patients. We established a final diagnosis of GS based on his history and genetic mutations.

Discussion and conclusion: To make a diagnosis of GS, many aetiologies should be excluded. Especially, Bartter syndrome is an important genetic disorder to distinguish. Especially, type III Bartter syndrome has similar features with GS, adult-onset, no growth retardation, preserved renal function and similar electrolyte abnormalities. To evaluate serum magnesium and urinary calcium excretion were important for the differential diagnosis. In this case, the serum magnesium was normal and urinary calcium excretion was not decreased. This case didn’t have classical features of GS. To identify the genetic mutation is very important to establish a diagnosis of GS. When the laboratory findings are not typical for GS, direct DNA sequencing can be useful test to distinguish with Bartter syndrome.