Background/Purpose:  Prior studies have shown that increased age at diagnosis and non-Caucasian race are associated with lower survival in polymyositis and dermatomyositis (PM/DM). However, itÕs unclear whether race is associated with differences in disease characteristics and response to treatment in PM/DM.  

Methods: This was a retrospective, observational cross-sectional study of 96 patients (62 African American (AA) and 34 Caucasian) with PM/DM seen in an academic rheumatology clinic from 1994 – 2016. Clinical characteristics were compared, and they included demographics, clinical and laboratory data at initial presentation to the clinic, and development of interstitial lung disease (ILD) (Table 1). Treatment medications (immunosuppressives (IS) and steroids), mean creatine kinase values (CK) in the last year of follow-up, and frequency of achieving stable disease state on or off medications (IS and steroids) in the last year of follow-up were compared between the groups to study treatment response (Table 2). Multivariate linear and logistic regression analysis was performed to determine factors that were associated with initial CK, presence of ILD and achievement of stable disease state during follow-up.

Results: Median CK was higher and rash was seen more frequently in AA patients at presentation than in Caucasians. The disease duration prior to the initial presentation was longer in AA patients. The AA and Caucasian patients did not differ in terms of frequency of dysphagia, autoantibodies at presentation, presence of ILD or age at diagnosis (Table 1). In a multivariable model, age at diagnosis was associated with initial CK (P = 0.0142) but other parameters including race did not correlate. During follow-up, the two groups were similar in terms of the number of IS used, and frequency of achieving stable disease state on or off medications in the last year of follow-up (Table 2). In a multivariable analysis, anti-Jo1 (OR 8.90, P = 0.00104) and SSA antibodies (OR 5.60, P = 0.00795) were associated with development of ILD. Presence of rash (OR 0.25, P = 0.00996), ILD (OR 0.24, P = 0.00738) and the number of IS used (OR 0.40, p=0.01199) were negatively associated with achieving stable disease state on or off medications in the last year of follow-up. Race was not a significant factor in either model.

Conclusion: The AA and Caucasian patients did not differ in terms of development of ILD or achieving stable disease state. Other parameters including presence of autoantibodies, rash and ILD and higher number of immunosuppresants used were associated with worse outcome. To our knowledge, this study included one of the largest AA PM/DM patient cohort to date.