Analysis of thiopurine S-methyltransferase phenotype-genotype in a Tunisian population with Crohn's disease.

This study was conducted to investigate the thiopurine S-methyltransferase TPMT activity distribution and gene mutations in Tunisian population with positive diagnostic for Crohn's disease. TPMT activity was measured in Tunisian population (n = 88) by a high performance liquid chromatography assay. Polymerase chain reaction-based methods were used to determine the frequency of TPMT mutant alleles TPMT*2, TPMT*3A, TPMT*3B and TPMT*3C. TPMT activity was normally distributed, ranging from 4.58 to 35.27 nmol/(h ml) RBC with a mean of 18.67 ± 7.10 nmol/(h ml) RBC. Seven TPMT*3A heterozygotes and one TPMT*3C homozygote were found in 88 patients, with allele frequencies of 0.039 and 1.13, respectively. TPMT*3A and the TPMT*3C, which cause the largest decrease in enzyme activity, were both variant alleles detected in the Tunisian population.