The Great Imitator - Disseminated Tuberculosis Presenting as Baker's Cyst: A Case Report

Tuberculosis is known to be a great mimicker, and it can present in a myriad of ways, which often result in an incorrect diagnosis. In a country that is endemic to tuberculosis, the presentation can take many forms ranging from tumour to trauma. We present a case of Baker's cyst that was provisionally diagnosed as pigmented villonodular synovitis (PVNS) of the knee and eventually turned out to be tuberculous arthritis. A 46-year-old male presented with an insidious swelling on the posterior aspect of his knee for one year. Magnetic resonance imaging was suggestive of PVNS as the likely diagnosis. The patient presented 21 days later with a foot drop. On following-up with further investigations, he was found to have a lesion at the level of the L4-L5 spine. Chest radiograph changes were suggestive of tuberculosis. A synovial biopsy of the knee was done, and the tuberculosis culture report was positive. The patient was started on anti-tubercular treatment and then operated on, with arthroscopic synovectomy and posterior open cyst excision. The histology report was positive for tuberculous synovitis. The patient completed the course of antitubercular drugs and had physiotherapy. He demonstrated a clinically and radiologically healed disease at the final follow-up with a good functional outcome. Clinicians must have a high index of suspicion for tuberculosis, especially in endemic areas. Getting a chest radiograph is recommended in every case. Early diagnosis with the appropriate treatment will give a good functional outcome for the patient.