Genotipo y fenotipo de la enzima tiopurina metiltransferasa en población chilena.
Palabras clave:
Drug hypersensitivity, Chile, Gentype, TPMT deficiency, PhenotypeResumen
PHENOTYPE AND GENOTYPE OF THIOPURINE METHYLTRANSFERASE IN CHILEAN INDIVIDUALS
Background: Thiopurines (azathioprine and 6-mercaptopurine) are highly effective medications but with potential adverse effects. Thiopurine methyltransferase (TMPT) is the key enzyme in their pharmacokinetics and is genetically regulated. A low activity of TPMT is associated with myelotoxicity. The genotype and enzyme activity can vary by ethnicity. Aim: To study the activity and genotype of TPMT in a group of Chilean subjects. Material and Methods: In 200 healthy adult blood donors, TPMT activity was determined by high performance liquid chromatography (HPLC). Deficient, low, normal or high levels were defined when enzymatic activity was ? 5, 6-24, 25-55 and ? 56 nmol/grHb/h, respectively. Genotyping of TPMT (*1, *2, *3A, *3B, *3C) was performed by PCR. Results: Seventy seven women (38.5%) and 123 men (61.5%), with an average age of 34.9 years were studied. Eighteen subjects (9%) had a low enzymatic activity, 178 (89%) had normal activity, 4 (2%) had high activity and no genotype deficient subjects were identified. The wild type genotype (*1) was found in 184 (92%) individuals and 16 (8%) were heterozygous for the variants: *2 (n=2), *3A (n=13) and *3C (n=1). No homozygous subjects for these variants were identified. Wild type genotype had an increased enzymatic activity (40.8±7.2 nmol/gHb/h compared to 21.2±3 nmol/gHb/h in the heterozygous group. p<0.001). Conclusions: Less than 10% of a Chilean population sample has a low enzymatic activity or allelic variants in the TPMT gene, supporting the use of thiopurines according to international recommendations.
