Predictive factors of rapidly progressive-interstitial lung disease in patients with clinically amyopathic dermatomyositis

Clinically amyopathic dermatomyositis (CADM) is a unique subset of dermatomyositis, showing a high incidence of lung involvements. The aim of this study is to identify risk factors, other than melanoma differentiation-associated protein (MDA)-5, for developing rapidly progressive-interstitial lung disease (RP-ILD) in patients with CADM. Forty CADM patients, in whom 11 patients developed RP-ILD, were enrolled. Clinical features and laboratory findings were compared between the patients with and without RP-ILD. We found that skin ulceration, CRP, serum ferritin, anti-MDA5 Ab, and lymphocytopenia were significantly associated with ILD. Multivariate logistic regression analysis indicated that anti-MDA5 Ab⁺, elevated CRP, and decreased counts of lymphocyte were independent risk factors for RP-ILD, which can provide a precise predict for RP-ILD in CADM patients. When anti-MDA5 Ab⁺ was removed from the multivariate regression model, using skin ulcerations, elevated serum ferritin and decreased counts of lymphocyte can also precisely predict RP-ILD. Except for MDA-5, more commonly available clinical characteristics, such as skin ulcerations, serum ferritin, and count of lymphocyte may also help to predict prognosis in CADM.