The association between scabies and myasthenia gravis: A nationwide population-based cohort study.

Scabies is an infectious inflammatory pruritic skin disease. Cytokine-mediated inflammatory processes contribute to the pathologic mechanism in scabies. Myasthenia gravis (MG) is also an autoimmune disease that is mediated by cytokines. The study aimed to investigate the association between scabies and myasthenia gravis. We conducted a nationwide population-based cohort study utilized data from the National Health Insurance Research Database (NHIRD) of Taiwan. Patients with scabies (n=5429) and control subjects without scabies (n=20,176) were enrolled. We tracked the subjects in both groups for a 7-year period to identify new onset MG. Cox regression analysis was performed to calculate the hazard ratio (HR) for MG. A total of 25,605 patients were enrolled in the study, including 5429 patients in the scabies group and 20,176 in the control group. There were 40 (0.7%) patients from the scabies group and 84 (0.4%) subjects from the control group who were newly diagnosed with MG during the 7-year follow-up period. The scabies patients had a significantly increased risk of MG, with an adjusted HR of 1.27 (95% confidence interval [CI] 1.01-1.89). As such, prompt diagnosis and treatment of scabies may decrease the risk of subsequent MG.