Genome-wide association study of atopic and autoimmune comorbidities in alopecia areata

Alopecia areata (AA) is a chronic autoimmune-mediated disorder characterized by hair loss from the scalp and/or body. AA patients frequently present with comorbid chronic inflammatory disorders (CIDs), particularly atopic and autoimmune diseases. Genome-wide association (GWA) studies have suggested a genetic link. However, no studies to date have examined genetic factors that are associated with the comorbid development of CIDs directly in individuals affected by AA.

We performed an exploratory GWA study in Central European AA patients stratified by self-reported comorbidity status (110 to 1,302 cases with- and 1,030 controls without comorbid CIDs). Comorbidities were analyzed first as broad atopic and autoimmune categories and subsequently as individual conditions, including asthma, atopic dermatitis, rhinitis, vitiligo, and Hashimoto's thyroiditis.

No genome-wide significant signals were identified at either the variant or gene level. At exploratory thresholds (p_variant<1x10^-5, p_gene<0.001), more loci showed potential association with comorbid autoimmunity than with atopy, although the number of implicated genes was comparable. Several identified genes were previously implicated in CID pathogenesis and many loci contained variants with known regulatory effects on gene expression in skin and immune cells. For comorbid atopy/autoimmunity overall, PHF11 was the most frequently implicated gene, consistent with its previously described role in T- and B-cell biology. Network analyses highlighted cytokine, hormone, and transcription factor signaling pathways as potential mechanisms underlying comorbid CID development in AA.

Our study provides initial mechanistic insights for comorbid CID development in AA, and a foundation for larger-scale studies.