Avaliação da influência de variantes genéticas do sistema dopaminérgico em sintomas de pacientes com TDAH

Abstract

Attention Deficit Hyperactivity Disorder (ADHD) is one of the most prevalent childhood psychiatric disorders, accounting for close to five percent of this population worldwide. ADHD is defined by levels, in regard to principles of inattention and/or hyperactivity/impulsivity, possessing great genetic susceptibility. The 48pb VNTR Variable Number Tandem Repeat) present in exon 3 of the DRD4 gene, the 40pb VNTR present in the 3'UTR of the DAT1 gene, and the Val158Met and Val66Met polymorphisms of the COMT genes and BDNF trials in the study by having association description in the literature with the symptoms of ADHD. A sample of 87 children was used in this study, and a continuous analysis of the symptoms of ADHD was performed in relation to the frequencies of the four polymorphisms. Allelic and genetic frequencies as well as the Hardy Weinberg equilibrium were calculated, with only non-DRD4 polymorphisms found out of balance. The absence of the 7R allele was related to a higher incidence of symptoms of destruction and combined than the 7R allele in homozygosis. The 10/10 homozygous genotype for the 40bp polymorphism of the DAT1 gene was also related to a higher incidence of the inattention symptoms and combined. There was no difference in the manifestation of symptoms of destruction and hyperactivity/impulsivity for the genotypes involving the Val66Met and Val158Met polymorphisms of the COMT and BDNF genes. The interaction between the four polymorphisms was not significant, and the influence of each variant was not affected by an influence of the others on the intensity of the symptoms. We also evaluated the environmental gene interaction in the manifestation of the symptoms, where it was not found. Based on the above, replication studies of these results are necessary for an understanding of the participation of genetic variants in the intensity of the symptoms of destruction and hyperactivity/impulsivity in childhood.