RESUMO
OBJECTIVE: To assess the frequency of the genetic markers HLA-DRB1 and DQB1 in patients with Graves' orbitopathy (GO) with and without extraocular muscle involvement. DESIGN: The frequencies of class II HLA-DRB1 and DQB1 allele groups were determined for 81 Brazilian patients with GO and 161 normal subjects. The patients were divided into myogenic and nonmyogenic groups based on the clinical characteristics of the orbitopathy and quantitative computed tomography analysis of the extraocular muscle (EOM) dimensions. MAIN OUTCOME: Compared to the frequency obtained for samples of normal subjects of the Brazilian population, HLA-DRB1 16 ( pc=0.008) was overrepresented in myogenic and HLA-DRB1 03 ( pc=0.02) in nonmyogenic patients. CONCLUSIONS: The association between the HLA-DRB1 16 and the myogenic subtype of GO suggests that EOM involvement in GO may be genetically predisposed.