Gas-filled parasymphyseal pubic cyst associated with degenerative joint disease.

Parasymphyseal cysts are a rare and poorly understood entity. This case report describes a gas-containing parasymphyseal cystic lesion associated with degenerative change and vacuum phenomenon in the pubic symphysis. The mass was discovered incidentally in a 72-year-old asymptomatic male who underwent a transrectal ultrasound-guided biopsy of the prostate and the nature of the lesion was confirmed on magnetic resonance imaging (MRI) and computed tomography (CT). We hypothesize that the gas within the parasymphyseal cystic mass arose from a vacuum phenomenon in the pubic symphysis, with subsequent extrusion of gas from the joint into the cyst itself. It is important for radiologists to be aware of the existence of this entity to avoid unnecessary surgery for patients.