Pulmonary actinomycosis presenting as post-obstructive pneumonia.

Actinomycosis is a chronic suppurative infection caused by filamentous Gram-positive bacilli, leading to a purulent discharge due to sulfur granule formation. Thoracic actinomycosis represents around 20% of Actinomyces infections, with endobronchial involvement being fairly uncommon. Pulmonary actinomycosis should be considered in the differential diagnosis of non-resolving lobar pneumonia or a lobar mass suspicious for malignancy on endobronchial biopsy. A case of endobronchial actinomycosis presenting as post-obstructive pneumonia and mimicking right upper lobe endobronchial carcinoma, which was associated with foreign body aspiration, is reported here.