Diagnostic utility of enzyme-linked immunospot assay for interferon-γ in a patient with tuberculous arthritis and pyomyositis

The indolent and nonspecific presentations of tuberculous arthritis and pyomyositis render their diagnosis a great challenge for clinicians. We describe a 78-year-old man with swelling and pain of right knee for 6 months. The patient was empirically treated for tuberculosis because positive enzyme-linked immunospot assay for interferon-γ of blood was reported at 2 days after aspiration of synovial fluid, which was negative for acid-fast stain but subsequently grew Mycobacterium tuberculosis 6 weeks later. He recovered uneventfully with 1-year antituberculous combination therapy.