Clinical characteristics of myositis patients with isolated anti-U1 ribonucleoprotein antibody resemble immune-mediated necrotizing myopathy

Background: Anti-U1 ribonucleoprotein (U1RNP) antibodies were associated with connective tissue diseases (CTDs), but the clinical characteristics of this antibody in Chinese myositis patients have not been studied. Objective: We aim to analyze features who test positive for anti-U1RNP and delineate a subgroup myositis. Design: This is retrospective cohort study. Methods: reviewed data compared them those anti-signal recognition particle (SRP) hydroxy-3-methylglutaryl-CoA reductase (HMGCR) antibody-associated immune-mediated necrotizing myopathy (IMNM). Results: A total 30 adult cases identified; median age was 47.5 years 24 (80%) females, 12 did coexist myositis-specific (MSAs) (isolated anti-U1RNP). The serum creatine kinase (CK) significantly higher isolated (2182.5 U/L versus 289 U/L, p = 0.01), number CK > 2000 that coexisting MSAs (66.7% 16.7%, 0.009). prevalence IMNM patients’ muscle pathology (75%, 0.003). Skin rashes less common group ( < 0.05). Of 25 individuals available pulmonary high-resolution CT (HRCT), 14 (56%) diagnosed interstitial lung disease (ILD). incidence muscular weakness, dysphagia, or levels different between anti-HMGCR SRP-IMNM groups But frequency Raynaud’s phenomenon, arthritis, membrane attack complex (MAC) deposits than (all 0.005). There no difference without Ro-52 Isolated showed marked improvements strength, remission rate 1 2 Conclusions: pathological similar IMNM. Arthritis ILD are most extramuscular features. Most respond well treatment good prognosis.