Overlooked Cause of Hypomagnesemia

Introduction: Hypomagnesemia can occur due to GI losses or renal wasting. Genetic causes of hypomagnesemia usually include Bartter/ Gitelman syndrome or isolated hypomagnesemia. We present a case of hypomagnesemia that was initially misdiagnosed as Gitelman syndrome , however later diagnosed as HNF1beta mutation. Case Description: A 25-year-old female with history of Gitelman syndrome presented to our hospital for evaluation of jaundice. Jaundice that began at age 17, with prior liver biopsies revealing idiopathic ductopenia. Nephrology was involved in the treatment of electrolyte abnormalities. At age 18, the patient was noted to have hypokalemia and hypomagnesemia with fractional excretion of magnesium at 32%. Renin was elevated and the patient was diagnosed with Gitelman syndrome. On admission, she was noted to have hypocalcemia which did not fit the diagnosis of Gitelman syndrome. Genetic testing was recommended in addition to replacing her electrolytes. Patient underwent a liver biopsy and genetic testing, and was eventually discharged on spironolactone, potassium chloride, oral magnesium and calcium carbonate supplementation along with outpatient appointment for iv magnesium infusions. She was readmitted for decompensated cirrhosis and acute kidney injury requiring renal replacement therapy and underwent liver transplantation. Kidney imaging revealed bilateral simple cysts measuring upto 2.1 cm. Genetic reports showed 17p-12 deletion syndrome which explained her liver and kidney disease. Patient to date continues to receive iv magnesium infusions weekly. She was recently started on dapagliflozin. Discussion: 17p-12 deletion encompasses 23 known genes, one of which includes hepatocyte nuclear factor 1 beta mutation. This mutation is associated with renal magnesium wasting due to dysfunction of distal convoluted tubule with 100% occurrence by at 13.8-18 years. These patients may be misdiagnosed as Gitelman syndrome, hence early recognition of this mutation in patients presenting with liver and kidney disease should be considered to avoid extensive diagnostic evaluation and economic burden to the health system.