Epidemiology of Antisynthetase Syndrome and Risk of Malignancy in a Population-Based Cohort (1998-2019)

Objective Population-based epidemiology studies about antisynthetase syndrome (ASyS) are lacking. Our aims were to determine the incidence and prevalence of ASyS and assess malignancy risk among patients following ASyS diagnosis. Methods A retrospective, population-based cohort of adults with incident ASyS residing in Olmsted County, Minnesota, in 1998-2019, was assembled. Fulfillment of Solomon classification criteria for ASyS and clinical data were collected by manual chart review. Patients were followed until death, migration from the area, or December 31, 2019. Malignancy was defined by physician diagnosis in the medical record. Incidence rate was age- and sex-adjusted to the 2010 US White population. Point prevalence rate was obtained on January 1, 2015. Results Thirteen patients with ASyS were identified (7 [54%] female, 13 [100%] White, median age 44.9 [IQR 41.9-58.3] years). The age- and sex-adjusted incidence of ASyS was 0.56 (95% CI 0.25-0.87) per 100,000 population. Incidence was highest in the 50-59 age group. Age- and sex-adjusted prevalence was 9.21 per 100,000 (95% CI 3.44-14.98). Two of 13 (15%) were diagnosed with malignancy within the follow-up interval and none within 3 years of ASyS diagnosis. At median 11.9 (IQR 7.0-13.4) years of follow-up, 12/13 (92%) of patients were alive. Conclusion ASyS is rare, with an incidence of 0.56 per 100,000 population and prevalence of 9.21 per 100,000. In this cohort, incidence was similar between male and female individuals, and was highest in persons aged 50-59 years. None of the patients developed malignancy within 3 years of ASyS diagnosis.