Resolution of Hypokalemia and Hypotension With Tacrolimus and Extrarenal Transplantation in Gitelman Syndrome

Gitelman syndrome (GS) is characterized by genetic mutations in the sodium chloride cotransporter (NCC), leading to renal potassium, sodium, and magnesium wasting. Calcineurin inhibitors recapitulate familial hyperkalemic hypertension, with gain of function of the NCC. Whether calcineurin inhibition can overcome fluid/electrolyte dyscrasias in GS is unknown. We describe a patient with GS initiated on tacrolimus, a calcineurin phosphatase inhibitor, after orthotopic heart transplantation. Potassium supplementation and potassium-sparing diuretics were discontinued with no consequential hypokalemia, and hypotension and hypomagnesemia also improved. This case provides proof of concept that calcineurin inhibitors may help overcome clinical sequelae of loss of function of NCC in GS.