A novel compound heterozygous variant of the SLC12A3 gene in Gitelman syndrome with diabetes and the choices of the appropriate hypoglycemic drugs: a case report

BACKGROUND: Gitelman syndrome (GS) is an autosomal recessive tubulopathy caused by mutations of the SLC12A3 gene. It is characterized by hypokalemic metabolic alkalosis, hypomagnesemia and hypocalciuria. It is universally known that both hypokalemia and hypomagnesemia can influence insulin secretion and insulin resistance, but the exact mechanisms require further study. We identified a novel deletion variant of the SLC12A3 gene and discussed the appropriate hypoglycemic drugs in Gitelman syndrome (GS) patients with type 2 diabetes. CASE PRESENTATION: A 55-year-old diabetic female patient was hospitalized for evaluation because of paroxysmal general weakness and numbness of extremities for one year. We suspected that she was suffering from GS by initial estimation. Direct Sanger sequencing was used to analyze the causative gene SLC12A3 of GS. Oral glucose tolerance test (OGTT) was carried out to assess the glucose metabolism and insulin resistance status. Genetic analysis revealed that she was a compound heterozygote for a recurrent missense mutation c.179C > T and a novel deletion c.1740delC in SLC12A3, thus her diagnosis of GS was confirmed. The patient was treated with potassium chloride (3.0 g/d) and magnesium chloride (element magnesium 350 mg/d) on the basis of initial treatment of diabetes with hypoglycemic drug (Repaglinide, 3.0 mg/day). However, she developed frequent hypoglycemia after one week. OGTT showed that her glucose metabolism and insulin resistance much improved after potassium and magnesium supplemental therapy. Then we changed the hypoglycemic agent to a dipeptidyl peptidase-4 (DPP-4) inhibitor (Trajenta 5 mg/d), since then her blood glucose level remained normal during two-year of follow-up. CONCLUSION: We have identified a novel deletion of the SLC12A3 gene and discussed the appropriate hypoglycemic drugs in Gitelman syndrome (GS) patients with type 2 diabetes. We suggested that attention need to be paid to blood glucose monitoring in GS patients, especially when hypokalemia and hypomagnesemia are corrected. Besides, the insufficient blood volume and serum electrolyte disturbance should also be taken into consideration in the selecting hypoglycemic drugs for GS patients.