TPMT (Thiopurine S-methyltransferase) is a very important enzyme for the metabolizm of thiopurine compounds. TPMT pharmacogenetics has been studied extensively because of its clinical significance. Many patients got benefited from the knowledge of TPMT genotype-phenotype correlation. Also, TPMT activity exhibits autosomal codominant genetic polymorphism, and patients inheriting TPMT-deficiency are at high risk of potentially fatal hematopoietic toxicity.Synonyms: Thiopurine S-methyltransferase