Lack of association between alopecia areata and HLA class I and II in a southeastern Brazilian population

Abstract

BackgroundAlopecia areata (AA) is a common disorder of unknown etiology that affects approximately 0.7% to 3.8% of patients among the general population. Currently, genetic and autoimmune factors are emphasized as etiopathogenic. Studies linking Human Leukocyte Antigens (HLA) to AA have suggested that immunogenetic factors may play a role in the disease's onset/development.ObjectivesTo investigate an association between AA and HLA class I/II in white Brazilians. Methods: Patients and control groups comprised 33 and 112 individuals, respectively. DNA extraction was performed by column method with BioPur kit. Allele's classification was undertaken using the PCR-SSO technique. HLA frequencies were obtained through direct counting and subjected to comparison by means of the chi-square test.ResultsMost patients were aged over 16, with no familial history, and developed partial AA, with no recurrent episodes. Patients showed a higher frequency of HLA-B*40, HLA-B*45, HLA-B*53 and HLA-C*04 compared with controls, although P was not significant after Bonferroni correction. Regarding HLA class II, only HLA-DRB1*07 revealed statistical significance; nevertheless, it featured more prominently in controls than patients (P=0.04; Pc=0.52; OR=0.29; 95%; CI=0.07 to 1.25). P was not significant after Bonferroni correction.ConclusionsThe development of AA does not seem to be associated with HLA in white Brazilians, nor with susceptibility or resistance. The studies were carried out in populations with little or no miscegenation, unlike the Brazilian population in general, which could explain the inconsistency found.

Joint study of the associations of HLA‐B and the transmembrane short tandem repeat polymorphism of MICA protein with alopecia areata shows independent associations of both with the disease

“…18 In a Brazilian population, there was a lack of association between AA and HLA class I and II alleles. 19 These different results indicate that the role of HLA class I in the immunopathogenesis of AA could be modulated by environmental factors, and based on the results of our study, possibly by MICA STR alleles that could be linked to several HLA-B alleles. Further study on this is warranted.…”

HLA-DRB1 polymorphisms and alopecia areata disease risk

“…Two allele families ( HLA-DRB1∗04 and HLA-DRB1∗16 ) conferred a significantly increased risk. For HLA-DRB1∗04 polymorphisms, the analysis of the pooled data of 8 case-control studies [ 9 – 16 , 20 ] revealed a significant increase in frequency (31.6% compared with 22.2% in controls), with an evidence of heterogeneity ( I 2 = 43.0%, P = .081). A random-effects model was used for calculating OR.…”

“…[ 12 – 14 ] However, the results were inconsistent with the findings of other studies. [ 15 – 20 ] Moreover, one study suggested a lower occurrence of HLA-DRB1∗15 polymorphisms in AA, [ 21 ] whereas others found no association. [ 13 , 15 , 16 , 18 – 20 ]…”

“HLA-C: evolution, epigenetics, and pathological implications in the major histocompatibility complex”

“…In a Brazilian population study, individuals with no familial history of alopecia areata but suffering from different degrees of this pathology were analyzed. They showed a higher frequency of the C*04 allele, but no other significant differences were found between the control groups (Barbosa et al, 2016). However, more recent studies that analyzed the top class I histocompatibility genes propose that HLA-A and B alleles represent a more significant risk factor than HLA-C alleles.…”