Incidence of autoimmune diseases in patients with scabies: a nationwide population-based study in Taiwan

Scabies is a commonly occurring infectious immune-mediated inflammatory skin disease. Immune-mediated inflammatory processes are also observed in autoimmune diseases. There have been very few previous studies; however, that have investigated the possible association between scabies and autoimmune diseases. To address this research gap, we conducted a nationwide population-based cohort study that included a total of 4481 scabies patients and 16,559 control subjects matched by gender, age, insured region, urbanization and income. We tracked both cohorts for a 7-year period to identify the incidence of autoimmune diseases in both groups during that follow-up period. Relatedly, a Cox regression analysis was performed to calculate and compare the hazard ratio (HR) for autoimmune diseases of both groups. An overall increased risk for 19 autoimmune diseases was observed in the scabies patients, with an adjusted HR (aHR) of 1.14 (95% CI 1.04-1.25). Compared with the control group, the scabies patients exhibited increased risks of hypersensitivity vasculitis (aHR 5.44, 95% CI 1.64-18.07), dermatomyositis (aHR 4.91, 95% CI 1.80-13.38), polyarteritis nodosa (aHR 2.89, 95% CI 1.46-5.73), systemic lupus erythematosus (aHR 2.73, 95% CI 1.33-5.64), psoriasis (aHR 2.31, 95% CI 1.85-2.88), myasthenia gravis (aHR 2.01, 95% CI 1.31-3.12), type 1 diabetes mellitus (aHR 1.93, 95% CI 1.53-2.44), pernicious anemia (aHR 1.92, 95% CI 1.42-2.61), and rheumatoid arthritis (aHR 1.43, 95% CI 1.12-1.83). In conclusion, the associations between scabies and a variety of autoimmune diseases may exist. Further studies are needed to clarify the shared etiologies and relationships between scabies and autoimmune diseases.