Utility of thiopurine methyltransferase genotyping and phenotyping, and measurement of azathioprine metabolites in the management of patients with autoimmune hepatitis.

Background/aims: Azathioprine is a key drug in the management of autoimmune hepatitis (AIH), with effects mediated via conversion to 6-thioguanine (6-TG) and 6-methylmercaptopurine (6-MMP), the latter controlled by thiopurine methyltransferase (TPMT). Our aims were to evaluate the role of TPMT genotyping and phenotyping and to examine 6-TG and 6-MMP metabolite levels in patients with AIH.

Methods: TPMT genotyping and phenotyping was performed on 86 patients with AIH, and metabolites evaluated in assessable patients.