Atypical Presentation of Giant Baker’s Cyst in a Patient with Enteropathic Arthritis

Baker’s cysts are synovial cysts caused by the enlargement of the gastrocnemio-semimembranosus bursa, presenting as painless or tender masses of the popliteal fossa, secondary to trauma, degenerative or inflammatory conditions. We report the case of a 54-year-old female patient with enteropathic arthritis presenting to our clinic with a disease flare characterized by peripheral arthritis of her wrists, knees and ankles with concurrent appearance of a non-tender mass in her right medial mid leg, measuring approximately 45 mm, without pain, fever or other symptoms. Previous history was remarkable for indolent non-Hodgkin’s follicular lymphoma and Crohn’s disease. An ultrasound confirmed that the medial mid leg mass was a giant Baker’s cyst measuring 150 mm. Corticotherapy and immunosuppression was initiated, concomitantly with US-guided aspiration resulting in progressive clinical and analytical improvement. This case depicts an uncommon presentation of a Baker’s cyst, with dimensions that can be explained by the underlying inflammatory condition. Baker’s cysts should be taken into consideration in the differential diagnosis of leg masses that also include entities with poorer outcomes.