Cancer risks among patients with alopecia areata: A population-based case-control study in Korea

To the Editor: Studies have shown the reduced incidence of skin cancer in patients with autoimmune dermatologic diseases, including alopecia areata (AA) and vitiligo.1,2 The aim of this study was to investigate the association between AA and several types of cancer. This study was a retrospective case-control study from the National Health Insurance Service–National Sample Cohort.3 Age, sex, location, income, and diagnostic codes based on the International Classification of Diseases, 10th edition were retrieved.