Thoracic Actinomycosis: A Rare Cause of Pleural Thickening

A middle-aged man presented with an indolent growth on his chest wall, features of sepsis, and constitutional symptoms. He was subsequently found to have raised inflammatory markers and pleural thickening on imaging which, coupled with a history of asbestos exposure, was concerning for malignancy. While there was clinical improvement with empirical intravenous penicillin antibiotics, the diagnosis was not certain until an excisional biopsy of the mass was performed, with histopathology showing Splendore Hoeppli material ('sulfur granules') leading to the diagnosis of an Actinomyces infection. The diagnosis allowed for appropriate management with a prolonged course of antibiotics, resulting in complete resolution of symptoms. This case highlights the importance of investigation for atypical infection in patients with pleural thickening, particularly in those with risk factors such as drug use.