Clinically amyopathic dermatomyositis (CADM) is a unique sub-type of idiopathic inflammatory myopathies with a high prevalence of interstitial lung disease (ILD). Poor prognosis of the patients was strongly associated with rapid progressive ILD. The aim of this study was to identify risk factors for prediction of different types of ILD in CADM.
In this study, data of 108 inpatients with CADM were collected, including 87 with ILD. The baseline clinical data and laboratory parameters, including myositis-specific and associated antibodies and tumor-associated antigens were analyzed to identify risk factors for acute or subacute interstitial pneumonitis (A/SIP) and chronic interstitial pneumonitis (CIP).
In 87 patients with CADM-ILD, 39 (36.1%) were A/SIP, and 48 (44.4%) were CIP. There were 22 (20.4%) patients with asymptomatic ILD who were detected by routine high resolution computed tomography. Cytokeratin-19 fragment (CYFRA21-1) was significantly higher in CADM-ILD than that in CADM patients without ILD; carcinoembryonic antigen and neuron-specific enolase were significantly elevated in A/SIP than that in CIP. Patients with A/SIP had a higher positive rate of anti-melanoma differentiation-associated gene 5 (MDA5), while patients with CIP had a higher positive rate of anti PL-12 and anti-Ro-52. Logistic regression analysis indicated that elevation of CYFRA21-1 was a risk factor for ILD, higher titer of anti-MDA5 indicated increased likelihood for A/SIP, and higher titer of anti-Ro-52 was also clearly associated with CIP.
This study indicated that the prevalence of ILD was high in CADM. Asymptomatic ILD has been previously underestimated. Anti-MDA5 was a risk factor for the presence of A/SIP, and CYFRA21-1 was a risk factor for ILD.