Gemcitabine-Induced Lung Injury Masquerading as ARDS in a Patient With Metastatic Renal Medullary Carcinoma: A Case Report.

Gemcitabine is widely used in the treatment of solid tumors, but pulmonary toxicity remains a rare and potentially life-threatening complication. We report the case of a woman with metastatic SMARCB1-deficient renal medullary carcinoma who developed acute hypoxic respiratory failure shortly after receiving combination gemcitabine and carboplatin. She presented with dyspnea, cough, fever, and diffuse pulmonary infiltrates initially attributed to multifocal pneumonia or emerging acute respiratory distress syndrome (ARDS). Respiratory viral testing was positive for rhinovirus, but bacterial cultures remained negative. Cardiac function was preserved, and pulmonary embolism was excluded. Computed tomography demonstrated diffuse lower lobe-predominant ground-glass opacities, patchy airspace disease, and peribronchial thickening with a small pleural effusion, consistent with noncardiogenic pulmonary edema or inflammatory lung injury. The temporal association with chemotherapy, absence of infectious or cardiogenic causes, and rapid clinical response to corticosteroids supported the diagnosis of gemcitabine-induced lung injury. Discontinuation of gemcitabine and initiation of systemic steroids resulted in significant clinical improvement. This case highlights the diagnostic challenges of gemcitabine pulmonary toxicity in patients with metastatic lung disease and concurrent viral infection.