Muscle strength recovery in patients with idiopathic inflammatory myopathy with different myositis-specific autoantibodies.

This study aims to assess muscle strength recovery in patients with idiopathic inflammatory myopathy (IIM) with three myositis-specific autoantibodies (MSAs). Forty-eight IIM patients (19 with anti-TIF1-γ Ab, 21 with anti-ARS Ab, and 8 with anti-SRP Ab) were included. Physical exercise began one week after starting medication. Muscle strength was measured using a hand held dynamometer. CK levels, muscle strength recovery, manual muscle test 8 (MMT8), and the Barthel index (BI) scores were evaluated before and after treatment among patients with anti-TIF1-γ, anti-ARS or anti-SRP Abs. CK levels decreased after one week of medication, and physical exercise did not worsen muscle involvement. Patients with anti-TIF1-γ and anti-ARS Abs exhibited rapid muscle strength improvement, while those with anti-SRP Ab had slower recovery. MMT8 followed a similar trend. BI scores significantly improved in patients with anti-TIF1-γ and anti-ARS Abs. All eight patients with anti-SRP Ab achieved a BI score of 100 despite no significant changes due to high variability. Muscle strength improved significantly, even in patients with a BI score ≤ 60. Muscle strength was recovered regardless of their MSA profile, and physical exercise may be safe for restoring muscle strength.