A case of rapidly progressive interstitial lung disease.

We describe a rare presentation of rapidly progressive interstitial pneumonia with autoimmune features (IPAF) associated with MDA5 autoantibodies. Unlike typical MDA5-positive dermatomyositis, this patient lacked skin or muscle involvement, expanding the clinical spectrum of this antibody-associated disease. An elderly male presented with acute-onset dyspnea and hypoxemic respiratory failure. High-resolution computed tomography revealed diffuse ground-glass opacities and interstitial changes. Autoimmune screening identified strongly positive anti-MDA5 antibodies, without clinical or laboratory evidence of dermatomyositis or other connective tissue diseases. The patient was diagnosed with MDA5-positive rapidly progressive interstitial lung disease (RP-ILD) manifesting as IPAF. Aggressive combination immunosuppressive therapy with high-dose corticosteroids, calcineurin inhibitor, and cyclophosphamide was initiated. Despite treatment, respiratory function deteriorated, and the patient succumbed to respiratory failure within weeks of presentation. MDA5-positive RP-ILD can present without classic dermatomyositis features. Early recognition of this antibody and prompt aggressive therapy are critical, though prognosis remains poor. This case underscores the need for heightened awareness and research into tailored treatment strategies.