Evidence of Th1/interferon (IFN)γ over-activation as major pathogenic driver somewhat conflicts with data supporting robust allergic background in alopecia areata (AA) patients. Previous investigations of immunologic dysregulations show both Th1 and Th2-related markers are over-expressed in AA. Clinical correlations in large populations may shed light on the immune pathways most likely to result in the clinical phenotype of AA.
To investigate the atopic comorbidities among patients with AA in a large, population-based study.
This is a cross-sectional retrospective study of AA patients and a matched comparison group, analyzing the associations between AA and four atopic comorbidities: asthma, atopic dermatitis (AD), allergic rhinitis, and allergic conjunctivitis. Chi-square and t-tests were used for univariate analysis, and logistic regression model was used for multivariate analysis. The study was performed utilizing the computerized database of Clalit Health Services ensuring 4.4 million subjects.
The study population includes 51,561 AA patients and 51,410 matched control subjects. The prevalence of asthma (7.8% vs. 6.5%; OR 1.22; 95%CI 1.17-1.28, p<0.001), AD (3.9% vs. 2.6%; OR 1.55; 95%CI 1.44-1.66, p<0.001), allergic rhinitis (16.0% vs. 12.8%; OR 1.29; 95%CI 1.25-1.34, p<0.001), and allergic conjunctivitis (23.5% vs. 19.6%; OR 1.27; 95%CI 1.23-1.30, p <0.001) was significantly higher among patients with AA as compared to matched control subjects. AA patients also had significantly higher probability to have more than one atopic comorbidity, with increasing OR as the number of concomitant atopic conditions increases.
Our analysis supports the previous literature and provides strong generalizability of significant atopy in AA patients, suggesting Th2 pathogenicity in AA, and challenging the traditional view of AA as a single axis, Th1-centered disease.

Copyright © 2020. Published by Elsevier Inc.