Clinical Manifestations and Myositis-Specific Autoantibodies Associated with Physical Dysfunction after Treatment in Polymyositis and Dermatomyositis: An Observational Study of Physical Dysfunction with Myositis in Japan

OBJECTIVE The physical function of PM/DM patients after remission induction therapy remains unknown adequately. The aim of our study was to evaluate the present status of physical dysfunction and to clarify the clinical manifestations and myositis-specific autoantibodies (MSAs) associated with physical dysfunction after treatment in PM/DM. METHODS We obtained clinical data including the age at disease onset, gender, disease duration, laboratory data prior to initial treatment, and the specific treatment administered. We evaluated disease activity and physical dysfunction after treatment using the core set provided by the International Myositis Assessment and Clinical Studies Group. RESULTS 57% of the 77 enrolled patients with PM/DM had troubles in daily living after treatment. At the enrolment, disease activity evaluated by physicians was only revealed in 20% of patients. In a multivariate analysis, the age at disease onset, female gender, and CK levels before treatment were significantly associated with the severity of physical dysfunction after treatment. Anti-SRP positivity was associated with more severe physical dysfunction after treatment than anti-ARS or anti-MDA5. CONCLUSIONS Half of the PM/DM patients showed physical dysfunction after treatment. Age at disease onset, gender, CK level before treatment, and anti-SRP were significant predictors associated with physical dysfunction after treatment in PM/DM.