Proteinuria in transplant patients associated with sirolimus

Sirolimus (SRL) is a potent immunosuppressive drug used in organ transplantation for prophylaxis of acute allograft rejection. Conversion from calcineurin inhibitors to SRL has become an important alternative in patients with chronic allograft nephropathy. Recently, some reports have described the appearance of proteinuria after the use of SRL. The aim of the present study was to describe the incidence of proteinuria in transplant recipients receiving SRL in our transplant center. We studied 78 patients receiving SRL either de novo or after conversion. Eighteen transplant recipients (23.1%) developed proteinuria after SRL treatment. Proteinuria was diagnosed at 11.2 +/- 2.1 months after the initiation of SRL; in eight patients (44.4%) it occurred in the first 6 months. The mean value of proteinuria was 2.6 +/- 0.6 g/24 hours. In 5 patients (27.8%), proteinuria reached nephrotic levels, and in 13 patients (72.2%) was associated with edema. Renal allograft biopsies were performed before conversion to SRL, and a new biopsy, after the appearance of proteinuria. The light microscopy of biopsies performed after the onset of proteinuria showed no specific glomerular changes, except in 2 cases wherein the diagnosis was focal segmental glomerulosclerosis. Immunofluorescence was negative in all cases. In conclusion, in this study proteinuria was observed in 21.3% of patients receiving SRL therapy either as de novo protocol or after conversion to SRL. Proteinuria occurred early after the initiation of SRL therapy and in these cases, withdrawal of SRL was associated with reversion of proteinuria.