HOMOZYGOTE THIOPURINE METHYL TRANSFERASE DEFICIENCY - A CONTRAINDICATION TO AZATHIOPRINE IN KIDNEY-TRANSPLANT RECIPIENTS

Azathioprine-induced myelosuppression is the mast important side effect observed in kidney transplantation. We report a case of severe neutropenia after kidney transplantation due to a thiopurine methyltransferase deficiency. This cause of azathioprine-induced myelotoxicity is rare, but its infectious consequences may be severe, Thiopurine methyltransferase deficiency must therefore be suspected when early and severe leukopenia occurs during azathiaprine therapy, Erythrocyte thiopurine methyltransferase activity measurement confirms the diagnosis. Azathioprine and 6-mercaptopurine must afterwards be definitively avoided.