Diffuse alveolar damage (DAD) is a pathological condition characterised by widespread injury to the alveolar epithelium and endothelium, leading to increased permeability, pulmonary oedema, and impaired gas exchange. It is clinically significant as it underlies acute respiratory distress syndrome (ARDS), a critical condition requiring prompt intervention. Commonly associated with sepsis, pneumonia, or trauma, DAD can result in long-term pulmonary complications, including fibrosis.