Primary cicatricial alopecia in a single-race Asian population: A 10-year nationwide population-based study in South Korea.

Primary cicatricial alopecia (PCA) is a dermatological challenge. Because no large-scale epidemiological study regarding PCA is available yet, we investigated the National Health Insurance Service-National Sample Cohort for patients diagnosed with PCA. The annual and overall rates of incidence and prevalence of PCA during the study period (2004-2013) were estimated. Distribution of PCA subtypes, disease co-occurrence rates and frequently prescribed medications were also evaluated. The overall incidence was 6.10 (95% confidence interval [CI], 5.62-6.60) per 100 000 person-years. The incidence rate was stable over time (risk ratio [RR] = 1.012, P = 0.201) and lower in female patients (RR = 0.718, P < 0.001). The overall prevalence was 20.93 (95% CI, 17.97-23.86) per 100 000 persons. The average duration of PCA was calculated as 3.23 years. Approximately 70% of the patients were below the age of 45 years. Folliculitis decalvans and dissecting cellulitis were the most common subtypes of PCA. Logistic regression analysis showed that PCA was significantly associated with thyroid disorders (adjusted odds ratio = 1.64, P < 0.001). Clobetasol was the most frequently prescribed topical agent. Corticosteroids were the most common oral agents used, followed by tetracycline antibiotics. Our study is the first large-scale study reporting the epidemiology of PCA. We found a preponderance of males and neutrophil-associated subtypes of PCA, and PCA was related to thyroid disorders.