An association between rheumatoid arthritis and scabies infection: A population-based study in Taiwan

Background: Scabies is an infectious inflammatory skin disease, and rheumatoid arthritis (RA) is also an immune-medicated inflammatory disease. Immune-mediated inflammatory processes result in the pathophysiologic mechanism in both diseases. Only a few studies have investigated the possible association between scabies and RA. Methods: This nationwide population-based study included 5135 patients with scabies as the study group; 19,115 people chosen from the National Health Insurance Research Database of Taiwan formed a control group. We tracked patients in both groups for 7 years to identify newly diagnosed cases of RA. Demographic characteristics and comorbidities were analyzed. Cox proportional hazards regressions were performed to calculate the hazard ratio (HR) of RA during the 7-year follow-up period. Results: Of the 24,250 patients enrolled in this study, 217 (0.9%) were diagnosed with RA during the 7-year follow-up period; 61 (1.2%) were from the scabies group and 156 (0.8%) were from the control group. The data showed that patients with scabies had a higher risk of subsequent RA, with an HR of 1.46 (95% confidence interval = 1.09–1.96). Conclusions: The results indicated an increased risk for RA among the patients with scabies infections. The data also showed that the assessment of RA symptoms should be included in the long-term follow-up of patients with scabies.