Polymyositis and dermatomyositis (PM-DM) are forms of idiopathic inflammatory myositis. Interstitial lung disease (ILD) in PM-DM is recognized as a serious complication and a major cause of death in this disease. In particular, patients with clinically amyopathic dermatomyositis (ADM) sometimes develop rapidly progressive ILD that remains unresponsive to intensive immunosuppresive therapy. A novel autoantibody associated with PM-DM was identified and termed anti-CADM-140/MDA5 antibody. Anti-CADM-140/MDA5 antibody titer correlates with disease activity and predicts the course of ILD associated with ADM. Glucocorticoids are considered the first-line drug treatment for PM-DM patients with ILD, however they are often not sufficient to obtain improvement of ILD as a single agent. Furthermore, the addition of immunosuppressive drugs becomes necessary as steroid sparing agents to avoid the severe side-effects often seen with high-dose steroid treatment. Cyclophosphamide, cyclosporin, and tacrolimus were reported to be effective in treatment of refractory ILD in PM-DM. Although other immunosuppressive agents; mycophenolate mofetil, intravenous immunoglobulin, and anti-TNF agents have appeared as promising agents for refractory PM-DM, the efficacy on ILD in PM-DM is still unknown. Even if treatment is initiated early in the course of the disease, some patients still develop irreversible fatal lung fibrosis under aggressive immunosuppressive therapy. Recently, cases with rapidly progressive ILD associated with clinically ADM were successfully treated with direct hemoperfusion with polymyxin B-immobilized fiber column.