Musculoskeletal involvement of tuberculosis is relatively uncommon. This is a case of disseminated tuberculosis presenting as left ankle monoarticular arthritis.
A 74-year-old woman who emigrated from Mexico 12 years ago presented with 6 months of left ankle pain and swelling. Because of limited mobility the patient had fallen and fractured her left hip. After surgical repair she was referred for further evaluation of her persistent left ankle symptoms. She had no other past medical history, and denied personal or exposure history to tuberculosis. Besides the left ankle symptoms, she also reported some weight loss and an occasional dry cough. There was no fever, chills, night sweats, rashes, or other joint or muscle pains. The physical exam was only significant for left ankle swelling, mild warmth, erythema, and tenderness to palpation and with movement of the joint. There was no leukocytosis, but calcium and alkaline phosphatase levels were elevated. Left ankle arthrocentesis produced a hazy serous fluid that contained predominantly lymphocytes and monocytes, with negative acid-fast-bacilli staining. The Quantiferon-TB Gold test was positive. Chest x-ray was abnormal, with a high-resolution computed tomography of the chest showing bilateral parenchymal nodules, areas of consolidation, and calcified lymphadenopathy. After multiple sputums were negative for acid-fast-bacilli, the patient underwent bronchoscopy with transbronchial biopsy. Empiric anti-tuberculosis therapy was also initiated. Since the bronchoalveolar lavage fluid and biopsy specimen were also stain-negative, yet suspicion for disseminated tuberculosis remained high, the patient underwent left ankle arthroscopy for synovial and bone biopsy. The Ziehl-Neelsen stain of the synovial biopsy sample was negative, but the Auramine-rhodamine stain was positive. One of the induced sputum samples started growing acid-fast bacilli at 11 days, with speciation confirming growth of Mycobacterium tuberculosis. The synovial fluid from the ankle arthroscopy also started growing acid-fast bacilli at 13 days.
Musculoskeletal tuberculosis is relatively uncommon, constituting 1–3% of tuberculous infections. Any bone, joint, or bursa can be involved, but 70% of musculoskeletal tuberculosis occurs in the spine, hips, or knees. During mycobacteremia of the primary infection, the tuberculosis bacilli spread to bone or joint spaces either hematogenously or via lymphatic spread. Reactivation of the disease can later lead to musculoskeletal tuberculosis. The diagnosis is often delayed because of the indolent course and low clinical suspicion. Spinal tuberculosis, or Pott’s disease, constitutes 40–50% of musculoskeletal tuberculosis. In endemic countries this disease occurs in older children and young adults, but in developed countries it is more commonly seen in older adults. Thoracic spine is involved in approximately 50% of the cases, with 25% of cases occurring each in lumbar and sacral spine. Extra-axial tuberculosis usually favors the weight-bearing joints, such as the hips and knees. There is usually only monoarticular involvement, with complaints of slowly progressive pain, swelling, and loss of function. Constitutional symptoms and active pulmonary disease are only seen in a minority of patients, and only 50% of these patients have chest x-ray abnormalities suggestive of tuberculosis. Synovial fluid analysis only has a sensitivity of approximately 79%. Acid-fast-bacilli stains are positive only in a minority of patients, and there are mixed results on the use of DNA amplification studies. Synovial or bone biopsy and culture are often needed for definitive diagnosis. The treatment of musculoskeletal tuberculosis is the same as the treatment of pulmonary tuberculosis. If treatment is initiated early the patient can often recover full joint function.
The diagnosis of musculoskeletal tuberculosis is clinically challenging. Work-up can be extensive, and a high clinical suspicion is needed.
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