Genetic analysis of thiopurine methyltransferase polymorphism in the Jordanian population

This study provides the first analysis of the TPMT mutant allele frequency in a sample of the Jordanian population and indicates that TPMT*3A is the most common allele in Jordanian subjects. Purpose Thiopurine methyltransferase TPMT catalyses the S -methylation of thiopurine drugs such as 6-mercaptopurine, 6-thioguanine, and azathiopurine. Thiopurine methyltransferase ( TPMT ) polymorphisms are the major determinants of interindividual differences in the severe haematological toxicity of 6-mercaptopurine. Several variants in the TPMT gene have been identified that correlate with a low activity phenotype. Four variant alleles, TPMT*2 , TPMT*3A , TPMT*3B and TPMT*3C , are responsible for over 80% of the low or undetectable enzyme activity. The allelic frequency of TPMT variants has been established in many populations. Methods In this study, the frequencies of four ( TPMT*2 , TPMT*3A , TPMT*3B and TPMT*3C ) variants were investigated in 169 healthy Jordanian men (18–45 years of age). Single nucleotide polymorphisms (SNPs) were genotyped using the Sequenom® MassARRAY technology (Sequenom®; San Diego, CA, USA). Results TPMT*3A and TPMT*3C were the only deficiency alleles detected in the Jordanian population with an allele frequency of 0.59% and 0.30% respectively. The TPMT*3A allele frequency is found to be lower than in the European Caucasian population. Conclusion TPMT*3A and TPMT*3C were the only deficiency alleles detected in the Jordanian population with an allele frequency of 0.59% and 0.30% respectively. The TPMT*3A allele frequency is found to be lower than in the European Caucasian population.