A Mimic of Metastatic Malignancy: Dietary Supplement-Associated Drug-Induced Lung Injury Presenting as Multiple Pulmonary Nodules With an Acute Fibrinous and Organizing Pneumonia Pattern.

Drug-induced lung injury (DILI) may present with diverse radiological and histopathological manifestations. We report a case of dietary supplement-associated DILI presenting as multiple randomly distributed pulmonary nodules mimicking metastatic malignancy and histopathologically exhibiting an acute fibrinous and organizing pneumonia (AFOP) pattern. A 62-year-old man who had taken a dietary supplement containing fermented grain extract, malt extract, and coenzyme Q10 for approximately 15 years developed multiple pulmonary nodules accompanied by marked peripheral eosinophilia. Computed tomography initially raised suspicion of metastatic malignancy. Bronchoalveolar lavage demonstrated eosinophilia, and transbronchial lung cryobiopsy revealed an AFOP pattern with prominent eosinophilic inflammation. The diagnosis of dietary supplement-associated DILI was established based on the exposure history, exclusion of alternative diagnoses, and spontaneous regression of the pulmonary nodules and improvement in eosinophilia following discontinuation of the dietary supplement. This case highlights that dietary supplement-associated DILI may mimic metastatic malignancy by presenting as multiple pulmonary nodules, while histopathological evaluation may reveal an AFOP pattern with marked eosinophilic inflammation.