Frequency of thiopurine S-methyltransferase (TPMT) alleles in southeast Iranian population

Thiopurine S-methyltransferase (TPMT, EC 2.1.1.67) plays a key role in the metabolism of thioprine drugs. Subjects with intermediate or no TPMT activity are at risk of azathioprines toxicity treated with conventional dosages of thiopurine drugs. While TPMT polymorphisms have been extensively studied in many countries, there is insufficient data in Iranian populations. In the present study, we aimed to identify the common functional TPMT alleles in southeast Iranian population. The TPMT allele frequencies were determined by multiplexed allele-specific polymerase chain reaction. Among 832 samples of Iranian population, the frequency for the TPMT*2, TPMT*3A, TPMT*3B and TPMT*3C, were 2.16%, 1.68%, 1.62%, and 0.54%, respectively. The distribution of the TPMT genotypes were 87.98% for TPMT*1/*1, 4.33% for TPMT*1/*2, 3.36% for TPMT*1/*3A, 3.24% for TPMT*1/*3B, and 1.08% for TPMT*1/*3C. This functional analysis of common TPMT alleles in an Iranian population could provide useful information for thioprine drugs therapy.