The impact of atopic dermatitis on alopecia areata: A 2-sample Mendelian randomization study

To the Editor: Previous studies have shown that patients with alopecia areata (AA) have an increased risk of atopic dermatitis (AD). 1 Kridin K. Renert-Yuval Y. Guttman-Yassky E. Cohen A.D. Alopecia areata is associated with atopic diathesis: results from a population-based study of 51,561 patients. J Allergy Clin Immunol Pract. 2020; 8: 1323-1328.e1 Abstract Full Text Full Text PDF PubMed Scopus (27) Google Scholar However, the genetic drivers of the relationship between AD and AA are largely unknown. Mendelian randomization (MR) uses genome-wide association studies (GWASs), thus eliminating environmental confounders, 2 Verbanck M. Chen C.Y. Neale B. Do R. Detection of widespread horizontal pleiotropy in causal relationships inferred from Mendelian randomization between complex traits and diseases. Nat Genet. 2018; 50: 693-698 Crossref PubMed Scopus (1916) Google Scholar to mimic randomized control trials by treating allele inheritance as simulated randomization (because alleles are inherited randomly, with high-risk alleles as a proxy for intervention) to assess their impact on certain outcomes, in this case, AD and AA.