Clinical Characteristics of Patients with Idiopathic Inflammatory Myopathy and Risk Factors for the Development of Interstitial Lung Disease

Abstract

Background Idiopathic inflammatory myopathy (IIM) is a group of connective tissue diseases characterized by muscle inflammation and muscle weakness, lung involvement is an important factor affecting the prognosis of patients. IIM can be classified into different clinical subtypes based on myositis-specific antibodies (MSAs), there are significant differences in clinical manifestations, organ involvement, prognosis and the risk of interstitial lung disease among different clinical subtypes. Objective To explore the characteristics of IIM and its different clinical subtypes, the risk factors for the development of interstitial lung disease. Methods The clinical data of patients hospitalizedin department of rheumatology and immunology of the First Affiliated Hospital of Kunming Medical University and diagnosed with IIM from April 2018 to February 2021 were collected. The included patients were divided into four clinical subtypes based on MSAs, including anti-MDA5-positive dermatomyositis (DM), anti-MDA5-negative DM, immune-mediated necrotizing myositis (IMNM) and anti-synthetase syndrome (ASS) subtypes. The general data, clinical manifestations, laboratory examination results were compared among different clinical subtypes. Multivariate Logistic regression model was established to explore the risk factors for ILD in patients with IIM. Results The 150 patients with IIM were divided into 4 clinical subtypes, including 30 patients with anti-MDA5-positive DM subtype (20.0%), 58 patients with anti-MDA5-negative DM subtype (38.7%), 14 patients with IMNM subtype (9.3%), and 48 patients with ASS subtype (32.0%). There were significant differences in the incidence of muscle weakness, myalgia, ILD, heliotrope rash, shawl sign, Gottron papules or Gottron sign, arthralgia, periungual red spot and dysphagia among the four clinical subtypes (P<0.05). The incidence of ILD in patients with anti-MDA5-positive DM and ASS subtypes was higher than patients with anti-MDA5-negative DM and IMNM subtypes, respectively (P<0.05) ; The incidences of heliotrope rash and shawl sign in patients with anti-MDA5-positive DM and anti-MDA5-negative DM subtypes were higher than patients with IMNM and ASS subtypes (P<0.05) ; The incidences of arthralgia in patients with anti-MDA5-positive DM subtype was higher than patients with anti-MDA5-negative DM subtype (P<0.05). There were significant differences in the levels of WBC, ALT, AST, serum creatinine, LDH, CK, C4, ferritin, T cell, CD8+ T cell, nature kill (NK) cell and incidence of ILD among patients with different subtypes (P<0.05). Multivariate Logistic regression analysis showed that anti-MDA5 antibody positive, anti-synthetase antibody positive, lung infection, ferritin>403.2 μg/L, IgG>14.15 g/L, LDH>359.5 U/L were all risk factors for ILD in IIM (P<0.05) . Conclusion The clinical manifestations of patients with different clinical subtypes differ significantly. DM patients with anti-MDA5 antibody positive are more likely to develop rash, arthralgia, ILD and leukopenia. MDA5 antibody positive, anti-synthetase antibody positive, lung infection and elevated ferritin, LDH and IgG levels are the risk factors for IIM with ILD.

Keywords

• idiopathic inflammatory myopathy|clinical subtypes|myositis-specific antibodies|interstitial lung disease|risk factors