Frequência dos alelos HLA-DQ2 e HLA-DQ8 associados com a doença celíaca em portadores de doenças autoimunes da tireoide

Abstract

Celiac disease (CD) is an immunological enteropathy characterized by typical intestinal histopathology with villous atrophy and small bowel mucosa crypt hyperplasia caused by ingestion of wheat gliadin in genetically predisposed individuals. The etiology of CD is composed of environmental and genetic factors. Regarding genetic factors, Human leukocyte antigen (HLA), gives 40% of the genetic variance. This susceptibility is associated with the HLA system, mainly with the DQA1 *05 and DQB1*02 alleles, which encode the DQ2 molecule and the DQB1*0302 and DRB1*04 alleles, which encoding the beta chain of the DQ8 molecule. The HLA-DQ test has diagnostic relevance because of the high negative predictive value in groups at risk for CD, including first-degree relatives and individuals with type 1 diabetes mellitus, autoimmune thyroid disease, Down syndrome, Turner syndrome, Williams or dermatitis herpetiformis. The European Society of Pediatric Gastroenterology Hepatology and Nutrition (ESPGHAN) recently proposed new criteria for the diagnosis of CD. Among these, screening for HLA-DQ2.5 and HLA-DQ8 in patients at risk for CD is a simple, less invasive and reliable method. Thus, the present study aimed to evaluate the prevalence of HLA alleles in patients with autoimmune thyroid disease attending the Nutrition and Endocrinology Outpatient Clinics of the Federal University of Pelotas. After the clarification and signing of the Informed Consent Form, the individuals answered a sociodemographic questionnaire and questions about their health. Subsequently, genomic DNA was extracted from buccal mucosa cells. For genotyping the DQA1*0501, DQB1*0201 and DRB1*04 alleles, polymerase chain reactions (PCR) with specific nucleotide primers were used. A total of 110 patients with DAT participated in this study. 66.4% of the individuals carried at least one of the studied alleles and 58.2% of the individuals were positive for at least one of the HLA-DQ2 alleles (DQA1*0501 and DQB1*0201). Regarding HLA-DQ8 (DRB1*04), 21.82% of the population studied were positive for this allele and 3.6% were positive for both HLA-DQ2 (DQA1*0501 and DQB1*0201) and HLA-DQ8 (DRB1*04). Genetic screening in this at-risk population is important because early diagnosis avoids morbidity and improves quality of life.