Thrombotic microangiopathy associated with combined sirolimus and tacrolimus immunosuppression after intestinal transplantation.

Calcineurin inhibitor-induced thrombotic microangiopathy (TMA) has been described in up to 14% of solid-organ transplant recipients. Sirolimus has recently been described in two reports in association with TMA. Sirolimus is known to potentiate cyclosporine-induced nephrotoxicity, but such effect has not been shown with tacrolimus. We report two intestinal transplant patients who developed TMA while on a tacrolimus and sirolimus immunosuppressive regimen. This syndrome appeared soon after institution of or increase in sirolimus dosage and improved only after this medication was discontinued.