Background/Purpose: Polymyositis (PM), dermatomyositis (DM), and clinically amyopathic DM (CADM) are systemic inflammatory diseases that affect skeletal muscle, skin, and other organs, such as lungs, heart, and joints. Several complications, such as interstitial lung disease (ILD), cardiomyopathy, and malignancy, are associated with poor prognosis for patients with PM/DM/CADM. Previous studies have highlighted the mortality and prognostic factors in PM/DM. Recently, myositis-specific autoantibodies (MSAs) have been used to predict clinical features, treatment response, and prognosis in patients with PM/DM/CADM. However, disease status after the treatment of adult patients with PM/DM/CADM, such as persistent existing disease activity or sustained remission, remains unclear in daily practice. Therefore, we investigated the disease status after treatment and clarified the predictive factors for sustained remission in adult patients with PM/DM/CADM using clinical data, including MSAs.

Methods: A total of 161 adult patients with PM/DM/CADM who visited our hospital from January 2001 to January 2017 were enrolled in this study. We retrospectively compiled clinical data, including age, gender, disease duration, organ involvement, MSAs, treatment history, and disease activity after treatment. Sustained remission was defined as following: any of active skin rash, such as Gottron’s papules/sign, heliotrope rash, and erythema, myositis, and ILD requiring treatment intensification were not revealed continuously for more than six months after one year since initiation of induction therapy for PM/DM/CADM.

Results: The number of patients with PM, DM, and CADM was 47, 85, and 29, respectively. The median duration of follow-up was 4 years. MSAs were identified in 102 patients. The prevalence of MSAs was as follows: anti-ARS antibody (Ab) in 40 (39%), anti-MDA5 Ab in 15 (15%), anti-TIF1-γ Ab in 12 (12%), anti-SRP Ab in 4 (4%), anti-NXP2 Ab in 4 (4%), and anti-SAE Ab in 2 (2%) patients. MSAs were negative in 25 (24%) patients. The total sustained remission rate was 58%. In patients with anti-ARS, anti-MDA-5, anti-TIF1-γ, or anti-SRP Abs, the sustained remission rate was 50%, whereas in those without any of these 4 MSAs, the sustained remission rate was 87%. Multivariate analysis revealed that the achievement of sustained remission was associated with absence of anti-ARS, anti-MDA5, anti-TIF1-γ, or anti-SRP Abs (Odds ratio = 6.7, 95% confidence interval (CI) = 1.7–33.0, P = 0.0045) and no complication of severe muscle weakness requiring assistance at the time of diagnosis (Odds ratio = 23.6, 95% CI = 2.6–618.2, P = 0.003).

Conclusion: The absence of anti-ARS, anti-MDA5, anti-TIF1-γ, and anti-SRP Abs and no complication of severe muscle weakness before initiation of treatment predict achieving sustained remission after treatment in adult patients with PM/DM/CADM.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/predictive-factors-for-achievement-of-sustained-remission-with-polymyositisdermatomyositis-a-retrospective-single-center-cohort-study-in-japan/