Bone marrow hypoplasia complicating tacrolimus (FK506) therapy

Tacrolimus (FK506)-induced hematological toxicity, which has rarely been reported in transplant recipients, may result in anemia episodes, reported mainly in kidney and heart transplant recipients, sporadic cases of thrombotic thrombocytopenic purpura/hemolytic uremic syndrome, red cell aplasia (4 reported cases), and generalized bone marrow suppression (only 1 reported case). We describe a case of a liver transplant recipient with pancytopenia that appeared during immunosuppressive therapy with tacrolimus. This patient suffered from progressive anemia, leukopenia with severe neutropenia, and mild thrombocytopenia; bone marrow biopsy showed hypoplasia (20% of cellularity) without dysplasia. Bone marrow recovery was made possible by suspending tacrolimus and changing to immunosuppression with cyclosporine A, despite the two drugs being very similar in their mechanism of immunosuppression. Contrary to previously reported cases (pure red cell aplasia and bone marrow hypoplasia), the recovery of hemoglobin and neutrophil values was slow after tacrolimus suspension, even though in the first month transfusions were no longer necessary.