Myositis-specific autoantibodies and their clinical associations in idiopathic inflammatory myopathies: results from a cohort from China.

Objectives: The purpose of this study was to determine the incidence of myositis-specific autoantibodies (MSAs) in a cohort of Chinese patients with idiopathic inflammatory myopathies (IIMs) and to examine their associations with clinical characteristics and long-term prognosis.

Methods: Adult patients with confirmed IIMs (n = 515) were studied using the EUROLINE Autoimmune Inflammatory Myopathies 16 Ag (IgG) commercial line blot test to detect MSAs/myositis-associated autoantibodies. We collected the laboratory data and clinical features. The frequencies of MSAs and their associations with clinical phenotypes were evaluated using SPSS 25.0 software.

Results: At least one MSA was found in 88.2% of the 515 IIM patients studied. The most frequently detected MSAs were anti-MDA5 (25.4%), anti-Jo-1(15.1%), and anti-EJ (9.5%). Autoantibodies against MDA5, TIF1-γ, and NXP2 were significantly correlated with cutaneous involvement (P < 0.001 or P < 0.01). Anti-TIF1-γ-positive patients had an enhanced risk of malignancy (OR = 3.51). Rapidly progressive interstitial lung disease (RP-ILD) was significantly correlated with anti-MDA5 (P < 0.0001). Anti-MDA5-positive patients had increased risks of elevated ferritin and decreased lymphocyte counts (OR = 5.65 and OR = 5.74, respectively). Kaplan-Meier survival revealed that individuals positive for anti-MDA5, especially anti-MDA5 combined with anti-Ro52, had the worst prognosis (P = 0.03). Male, old age, RP-ILD, and elevated ferritin were identified as predictors of poor prognosis in IIM patients.

Conclusions: MSAs were present in the majority of the IIM patients. Numerous MSAs were independent factors for identifying exceptional clinical phenotypes. Key Points • This is a large Chinese cohort of IIM patients to analyze possible associations of MSA profiles with clinical characteristics, aiming to provide valuable data for clinical work. • MSAs were present in approximately 90% of IIM patients with distinct clinical subsets. Patients with anti-Jo-1 and non-anti-Jo-1 ASAs exhibited similar characteristics. • The association of anti-TIF1-γ with malignancy was confirmed in adult patients. Patients with IIMs who were positive for both anti-Ro52 and anti-MDA5 had a worse prognosis. • Male, RP-ILD, and heliotrope rash were independent risk factors for a poor prognosis in patients with IIMs.