Long-term pulmonary outcomes and mortality in idiopathic inflammatory myopathies associated with interstitial lung disease

ObjectiveTo study prognostic factors in different types of idiopathic inflammatory myopathies (IIM) associated with interstitial lung disease (ILD).Patients and methodsMulticenter retrospective study of a Spanish cohort of patients diagnosed with IIM. Patients were classified into four categories: polymyositis (PM), dermatomyositis (DM), antisynthetase syndrome (ASS), and overlap myositis (OM). Sociodemographic data, clinical characteristics, antibodies, and treatments were collected. Cox regression models were calculated to identify factors associated with mortality, the necessity for long-term oxygen therapy (LTOT), and deterioration in respiratory function tests (RFT).ResultsThe number of patients included was 478, of whom 112 (23.4%) suffered from ILD: 17% PM, 16% DM, 45% ASS, and 22% OM. Factors associated with mortality in the multivariate analysis were clinically meaningful progression of ILD after 3months (CMP 3m) (hazard ratio (HR) 9.48, p=0.005), severe infections (HR 6.41, p=0.016), heliotrope erythema (HR 31.1, p=0.002), delay in diagnosis (HR 1.29; p=0.011), and Raynaud's phenomenon (HR 11.9, p=0.007). However, being female (HR 0.19, p=0.044) and positivity solely for ANAs (HR 0.08, p=0.008) presented a protective effect. CMP 3m (HR 22.7, p=0.027) was associated with the need for LTOT, while basal aldolase (HR 0.90; p=0.049) had a protective effect. Likewise, joint manifestations (HR 0.04, p=0.034) were shown to reduce risk of deterioration in RFT.ConclusionsCMP 3m, severe infections, delay in diagnosis, heliotrope erythema, and Raynaud's phenomenon were identified as factors of poor prognosis in different IIM associated with ILD.