Clinical and Genetic Characteristics in Patients With Gitelman Syndrome

Introduction: Gitelman syndrome (GS) is a tubulopathy exhibited by salt loss. GS cases are most often diagnosed by chance blood test. Aside from that, some cases are also diagnosed from tetanic symptoms associated with hypokalemia and/or hypomagnesemia or short stature. As for complications, thyroid dysfunction and short stature are known, but the incidence rates for these complications have not yet been elucidated. In addition, no genotype-phenotype correlation has been identified in GS. Methods: We examined the clinical characteristics and genotype-phenotype correlation in genetically proven GS cases with homozygous or compound heterozygous variants in SLC12A3 (n = 185). Results: In our cohort, diagnostic opportunities were by chance blood tests (54.7%), tetany (32.6%), or short stature (7.2%). Regarding complications, 16.3% had short stature, 13.7% had experienced febrile convulsion, 4.3% had thyroid dysfunction, and 2.5% were diagnosed with epilepsy. In one case, QT prolongation was detected. Among 29 cases with short stature, 10 were diagnosed with growth hormone (GH) deficiency and GH replacement therapy started. Interestingly, there was a strong correlation in serum magnesium levels between cases with p. Arg642Cys and/or p. Leu858His and cases without these variants, which are mutational hotspots in the Japanese population (1.76 mg/dl vs. 1.43 mg/dl, P < 0.001). Conclusion: This study has revealed, for the first time, clinical characteristics in genetically proven GS cases in the Japanese population, including prevalence of complications. Patients with hypokalemia detected by chance blood test should have gene tests performed. Patients with GS need attention for developing extrarenal complications, such as short stature, febrile convulsion, thyroid dysfunction, epilepsy, or QT prolongation. It was also revealed for the first time that hypomagnesemia was not severe in some variants in SLC12A3.