[Analysis of genetic polymorphisms of thiopurine S-methyltransferase (TPMT) in Mexican pediatric patients with cancer].

Background: Thiopurine S-Methyltransferase (TPMT) catalyses the S-methylation of thiopurine drugs, such as 6-mercaptopurine, 6-thioguanine and azathioprine, leading to their inactivation. Individuals who carry TPMT allele variants are more likely to experience life-threatening toxicity when these drugs are given at a standard dose. Wildtype phenotype TPMT*1 exhibits high level of catalytic activity, while all variants manifest with a decreased enzymatic activity.