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

Azathioprine-induced myelosuppression is the mast important side effec t observed in kidney transplantation. We report a case of severe neutr openia after kidney transplantation due to a thiopurine methyltransfer ase deficiency. This cause of azathioprine-induced myelotoxicity is ra re, but its infectious consequences may be severe, Thiopurine methyltr ansferase deficiency must therefore be suspected when early and severe leukopenia occurs during azathiaprine therapy, Erythrocyte thiopurine methyltransferase activity measurement confirms the diagnosis. Azathi oprine and 6-mercaptopurine must afterwards be definitively avoided.