Association analysis of IL1A and IL1B variants in alopecia areata

Alopecia areata is an inflammatory hair loss disease with a major genetic component. The disease is characterized by focal inflammatory lesions with perifollicular T-cell infiltrates, reflecting the role of local cytokine production in the development of patchy hair loss. IL-1 alpha and IL-1 beta are important inhibitors of hair growth in vitro. Their effect is opposed by the interleukin-1 receptor antagonist, IL-1ra. Genes of the IL-1 cluster are candidate genes in the pathogenesis of alopecia areata. To investigate the role of the IL-1 system in alopecia areata we examined three biallelic polymorphisms within the IL-1 gene cluster (IL1A+4845, IL1B+3954 and IL1B-511) in 165 patients and a large number of matched controls (n=1150). There was no significant association of IL1B-511 or IL1B+3954 genotypes with the overall dataset, or with disease severity or age at onset, in contrast with a previous report. The results suggested the possibility of an association with IL1A+4845 in the overall dataset [OR 1.39 (95% CI 1.00, 1.93)] although this was not statistically significant. This was due mainly to the contribution from mild cases of alopecia areata [OR 1.48 (0.96, 2.29)], suggesting that IL-1 alpha may have a particular role in the pathogenesis of this subgroup.