Mediastinal actinomycosis masquerading as a mass: a case of progressive dysphagia in an immunocompromised patient.

Actinomycosis is a rare endogenous infection characterised by indolent progression, contiguous spreading, abscess formation and draining sinuses. Here, we present a case of Schaalia odontolytica causing a mediastinal abscess that is unique in its acuity and location. Our patient presented with worsening dysphagia, and CT of her chest revealed a new mass in the posterior mediastinum displacing the oesophagus. Oesophagram revealed mild motility disorder, but no masses or ulcers within the oesophagus. Oesophagogastroduodenoscopy with endoscopic ultrasound revealed extrinsic compression of the oesophagus. Fine-needle aspiration of the mass yielded purulent fluid, which was cultured. A single colony of S. odontolytica was isolated. Initially, medical treatment was favoured, but as she developed worsening dysphagia, the abscess was drained. She continued on long-term antibiotic therapy after drainage and had complete resolution of the abscess at 1 year.