TPMT and Hepatitis: In patients with mutations in the thiopurine S-methyltransferase (TPMT) gene that alter the metabolism of azathioprine and result in greater drug exposures and higher risk of azathioprine-induced toxicity, other T-lymphocyte–modulating agents such as mycophenolate, sirolimus, cyclosporine, and tacrolimus have been reported to remit liver inflammation (12).