Enhertu-Induced Cryptogenic Organizing Pneumonia: Case Report and Review

Trastuzumab deruxtecan (T-DxD, Enhertu) is a HER2-directed antibody–drug conjugate that has expanded treatment options for patients with HER2-positive and HER2-low breast cancer. However, its use is associated with interstitial lung disease (ILD), most commonly manifesting as cryptogenic organizing pneumonia (COP), which can be life-threatening. We present the case of a 41-year-old woman with a history of invasive ductal carcinoma of the breast who developed acute dyspnea one week after her first dose of Enhertu. High-resolution chest computed tomography revealed radiographic features consistent with organizing pneumonia, along with metastatic disease and left hemidiaphragm paralysis. This case highlights the critical importance of early recognition and management of Enhertu-induced ILD. A review of the literature underscores the need for vigilant surveillance, timely imaging, and prompt initiation of corticosteroid therapy to mitigate morbidity and mortality. Enhertu represents a major therapeutic advance, but its pulmonary toxicity necessitates a structured, multidisciplinary approach to patient monitoring and care.