RESUMO
Introduction Tuberculosis of the soft tissues is a rare form of extra pulmonary tuberculosis, and isolated localization in the popliteal fossa is particularly exceptional. Atypical clinical presentation can lead to delayed diagnosis and serious complications. Case report We report the case of a 17-year-old patient who was diagnosed with tuberculosis of the popliteal fossa. He presented with a painful inflammatory swelling of the right popliteal fossa associated with a homolateral inguinal lymph node, without knee joint effusion. Standard chest and knee X-rays were normal, while MRI showed an 8 cm well vascularized, partly liquefied mass in the popliteal fossa, developed in contact with the semimembranosus and medial gastrocnemius muscles, associated with a popliteal lymph node without synovial effusion or thickening. Microbiological tests did not isolate any germs. The diagnosis was made on histological examination after biopsy, which revealed a caseous granuloma surrounded by epithelioid cells. The patient was treated with anti-tuberculosis therapy for 9 months. The clinical and radiological regression of the swelling was observed without recurrence at 2 years of follow-up. Conclusion Any soft tissue abscess should raise suspicion of tuberculosis, especially in endemic countries. The importance of histopathological examination should be emphasized to establish the diagnosis in the absence of signs in favor of a primary localization.