Anti-melanoma differentiation-associated gene 5 (anti-MDA5) antibody is associated with rapidly progressive interstitial lung disease (RP-ILD) in patients with clinically amyopathic dermatomyositis (CADM) or dermatomyositis (DM). We herein report three Japanese cases of anti-MDA5 antibody-positive RP-ILD without signs of CADM or DM. High-resolution computed tomography revealed patchy or subpleural distribution of consolidations and/or ground-glass opacities accompanied by traction bronchiectasis. All patients succumbed to respiratory failure within two months. Anti-MDA5 antibody-positive RP-ILD without signs of CADM or DM should be included in the differential diagnosis of acute/subacute ILD. Measurement of anti-MDA5 antibody and an intensive immunosuppressive regimen might rescue these patients from RP-ILD.
Keywords: acute interstitial pneumonia; anti-melanoma differentiation-associated gene 5; clinically amyopathic dermatomyositis.