[Hyperkalemia in a cyclosporine A-treated allogeneic bone marrow transplant recipient]

A 9-year-old boy was admitted with the diagnosis of myelodysplastic syndrome (FAB RAEB in T). The patient was treated with busulfan and cyclophosphamide and transplanted with bone marrow cells from an HLA identical sister. Cyclosporin A (CyA) and short term methotrexate (MTX) was given for prophylaxis against graft versus host disease (GvHD). The serum potassium value was observed to increase to 6.3 mEq/l during the period of CyA therapy. The serum potassium value returned to 4 mEq/l when CyA treatment was decreased to a serum concentration of less than 50 ng/ml (FPIA). On day 90 post transplantation the patient was diagnosed as relapsed. The patient was preconditioned with cyclophosphamide and total body irradiation and a second bone marrow transplantation was performed using cells from the same donor. He was treated again with CyA and short term MTX for the prevention of GvHD. Once again the patient became hyperkalemic with 6.8 mEq/l. The serum creatinine level was 0.9 mg/dl, the GFR was 52.1 ml/min, FEK was 7.1%. Pseudohypoaldosteronism or hyporeninemic hypoaldosteronism was suspected. To investigate this possibility a renin/aldosterone stimulation test was performed. We speculate that an idiosyncratic response to CyA resulted in pseudohypoaldosteronism and produced a defect in potassium secretion.