Association of Actinic Keratosis with Rheumatoid Arthritis and Psoriasis: A Nationwide Population-Based Study in Korea.

There have been no epidemiological studies identifying associations between systemic inflammatory diseases and actinic keratosis. This study used a large nationwide database to investigate the associations between actinic keratosis and systemic inflammatory diseases. Records of patients over 20 years of age newly diagnosed with actinic keratosis (n = 64,659) from 2012 to 2017 were analysed. A control population of individuals without actinic keratosis, matched for age, sex, and year of claim, who visited an outpatient clinic, was sampled at a ratio of 1:1 (n = 64,659). Both cohorts were analysed for the presence of systemic inflammatory diseases within at least 5 years prior to diagnosis of actinic keratosis. Patients with actinic keratosis exhibited higher odds ratios for rheumatoid arthritis (1.336; 95% confidence interval (95% CI) 1.161-1.537)) and psoriasis (1.513; 95% CI 1.435-1.595) compared with the control group on multivariate analysis. However, the proportions of Behçet's disease, Crohn's disease, ulcerative colitis, and multiple sclerosis in the actinic keratosis group were not statistically significant.