Background/Purpose: PM and DM are inflammatory myopathies, sometimes complicated by interstitial lung disease (ILD), myocarditis, arthritis, and malignancies. The intensity of immunosuppressive therapies depends on the severity of muscle weakness and organ complications associated with PM/DM in individual patients. Corticosteroids remain the mainstay of treatment for PMDM, although immunosuppressive agents have also been administered to better control disease activity and taper the dose of prednisolone (PSL) as much as possible. Long-term usage of PSL could cause a wide range of complications such as steroid myopathy, infection, osteoporosis, and diabetes mellitus. However, in daily clinical practice, it is difficult for some patients with PM/DM to taper PSL dose because of disease activity or repetitive recurrence despite combination therapy with immunosuppressants. Therefore, we clarified the required dose of PSL as maintenance therapy and investigated factors associated with the maintenance PSL dose in patients with PM/DM.

Methods: A total of 133 patients with PM/DM, who visited our hospital from January 2001 to January 2017 and had been treated for more than one year after initiation of therapies for PM/DM, were enrolled in this study. We retrospectively compiled clinical data, including age, gender, muscle strength, organ complications, laboratory data, including myositis-specific autoantibodies (MSAs), and treatment content. We investigated factors associated with the requirement of >5 mg/day of PSL, using multiple logistic regression analysis.

Results: The number of patients with PM, DM, and clinically amyopathic DM was 41, 69, and 23, respectively. The median follow-up duration was 4 years. ILD was observed in 76 (57%), dysphagia in 23 (17%), and malignancies in 29 (22%) patients. The median initial PSL dose was 50 mg/day. Methyl-PSL pulse therapy was performed in 45 (34%) patients. Immunosuppressants, including MTX, AZA, cyclophosphamide, and calcineurin inhibitors, and IVIG were administrated in 94 (71%) and 19 (14%) patients, respectively. The median maintenance PSL dose was 5 mg/day (interquartile range: 2–8 mg/day). The requirement of >5 mg/day of PSL as maintenance therapy was found in 52 patients (39%). In multivariate analysis choosing age, gender, disease duration, myositis type, MSAs, treatment content, and follow-up period as explanatory variables, the presence of anti-ARS antibody (Ab) was a significant factor associated with the requirement of >5 mg/day of PSL (Odds ratio = 6.3, 95% confidence interval = 1.5–33.1, P = 0.01). There were no other statistically significant factors. The requirement of >5 mg/day of PSL was found in 23 (59%) patients with anti-ARS Ab, but only in 13 (24%) patients without anti-ARS Ab (P < 0.001).

Conclusion: In most patients without anti-ARS Ab, it is possible to decrease the maintenance PSL dose to ≤5 mg/day. The presence of anti-ARS Ab is associated with difficulty of tapering PSL dose to 5 mg/day despite combination therapy with PSL and immunosuppressants.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/analysis-of-required-dose-of-corticosteroid-as-maintenance-therapy-and-related-factors-in-patients-with-polymyositisdermatomyositis/