Pulmonary Actinomycosis: A Diagnostic Challenge

Pulmonary actinomycosis is an uncommon and challenging infectious disease with non-specific symptoms and imaging findings. The authors report a case of a 68-year-old man with diabetes and a history of past smoking who presented with anorexia and weight loss with no significant findings on physical examination. A parenchymal consolidation in the anterior segment of the right upper lobe was detected after a chest computed tomography (CT). Bacterial colonies of Actinomyces species were identified in the histology of transbronchial biopsy. Imaging reassessment after six weeks of treatment with oral amoxicillin showed progression with a high metabolism 10.5 standardized uptake value (SUV) documented on the f-fluorodeoxyglucose positron emission tomography/CT. Concern about the possibility of lung cancer was raised and ruled out by a negative transthoracic needle biopsy. The diagnosis of pulmonary actinomycosis with pyogenic superinfection was presumed. The patient was successfully treated with intravenous amoxicillin and clavulanate for two weeks, followed by six months of oral treatment.