Gitelman syndrome with Graves' disease leading to rhabdomyolysis: a case report and literature review.

A 14-year-old male patient who suffered from limb numbness, fatigue, and hypokalemia was considered Graves' disease (GD) complicated with thyrotoxic periodic paralysis (TPP) at the first diagnosis. Although with the treatment of antithyroid drugs, he developed severe hypokalemia and rhabdomyolysis (RM). Further laboratory tests revealed hypomagnesemia, hypocalciuria, metabolic alkalosis, hyperrenin, and hyperaldosteronemia. Genetic testing revealed compound heterozygous mutations in the SLC12A3 gene (c.506-1G > A, c.1456G > A) encoding the thiazide-sensitive sodium-chloride cotransporter, which presented a definitive diagnosis of Gitelman syndrome (GS). Moreover, gene analysis revealed his mother diagnosed with subclinical hypothyroidism due to Hashimoto's thyroiditis carried the c.506-1G > A heterozygous mutation in the SLC12A3 gene and his father carried the c.1456G > A heterozygous mutation in the SLC12A3 gene. His younger sister who had hypokalemia and hypomagnesemia carried the same compound heterozygous mutations as the proband and was diagnosed with GS as well, but with a much milder clinical presentation and better treatment outcome. This case suggested the potential relationship between GS and GD, clinicians should strengthen the differential diagnosis to avoid missed diagnosis.