Genetic association of HLA-DQB1 and HLA-DRB1 polymorphisms with alopecia areata in the Italian population

Background Alopecia areata (AA) is a multifactorial disease characterized by hair loss especially from the scalp. As for other autoimmune conditions, the major histocompatibility complex (HLA) region is associated with AA susceptibility. Objective To provide evidence for the association of specific HLA-DQB1 and HLA-DRB1 alleles with AA in an Italian population, using a case-control approach. Methods We performed a case-control study to investigate whether HLA-DQB1 and -DRB1 alleles predispose to AA in the Italian population. HLA class II typing was performed in 85 patients with AA and 210 healthy controls from the same ethnic group. Results An increased frequency of DQB1*03, coding for DQ7 heterodimers, and a decreased rate of the DQB1*06 allele were observed in patients when compared with controls; the greatest and significant difference was in the group of cases with a more severe phenotype [AA > 50% patients (more than 50% hair loss) vs. controls, P = 4.5 x 10(-3), P(c) = 0.031, odds ratio (OR) 2.01, 95% confidence interval (CI) 1.22-3.31 and P = 2.5 x 10(-3), P(c) = 0.017, OR 0.22, 95% CI 0.07-0.72, respectively]. DQB1*03, serologically related to DQ8 or coding for DQ9 molecules, was not associated with AA susceptibility. Out of all patients, 65.9% carried DQ7 heterodimers compared with 49.5% of the controls (P = 7.3 x 10(-3), OR 1.97, 95% CI 1.17-3.32) and DQ7 prevalence rose to 76.3% in patients with AA > 50% (P = 1.7 x 10(-3), OR 3 28, 95% CI 1.48-7.27). No significant difference was found in the distribution of DRB1 variants or phenotypes among cases and controls. Conclusion Our data show a correlation between the HLA-DQB1 locus and the occurrence of AA in Italy supporting DQB1*03(DQ7) as a predisposing allele for the disease and the relevance of the HLA genetic test in the clinical management of AA.