Prevalence and Incidence of Comorbid Diseases and Mortality Risk Associated with Lichen Planopilaris: A Korean Nationwide Population-Based Study

Various comorbid diseases have been reported in patients with lichen planopilaris (LPP); however, data regarding the risks of incident diseases and mortality are lacking. This was a retrospective nationwide population-based study, using data from the National Health Insurance Service Database of Korea from 2002 to 2019. Patients aged ≥18 years with ≥3 documented medical visits for LPP were included. The adjusted hazard ratios (aHRs) for incident disease outcomes and mortality were compared with 1:20 age-, sex-, insurance type-, and income level-matched controls. In total, 2,026 patients with LPP and 40,520 controls were analysed. The risks of incident systemic lupus erythematosus (aHR, 1.91; 95% confidence interval [CI], 1.21-3.03), psoriasis (aHR, 3.42; 95% CI, 2.83-4.14), rheumatoid arthritis (aHR, 1.39; 95% CI, 1.19-1.63), lichen planus (aHR, 10.07; 95% CI, 7.17-14.15), atopic dermatitis (aHR, 2.15; 95% CI, 1.90-2.44), allergic rhinitis (aHR, 1.29; 95% CI, 1.13-1.49), thyroid diseases (hyperthyroidism [aHR, 1.42; 95% CI, 1.14-1.77], hypothyroidism [aHR, 1.19; 95% CI, 1.01-1.41], and thyroiditis [aHR, 1.35; 95% CI, 1.08-1.69]), non-melanoma skin cancer (aHR, 2.33; 95% CI, 1.00-5.44), and vitamin D deficiency (aHR, 1.23; 95% CI, 1.03-1.47) were higher in patients with LPP. Patients with LPP had a higher mortality rate than controls (aHR, 1.30; 95% CI, 1.04-1.61), although the risk was not significant after adjusting for comorbidities (aHR, 1.08; 95% CI, 0.87-1.34). Patients with LPP had a higher risk of various diseases following LPP diagnosis. Close follow-up is needed to optimize comprehensive patient care.