A 68-year-old male was admitted to the orthopedic trauma service for chronic pain and swelling of the tarsal portion of his foot.
The appearance of mechanical pain at the right foot tarsus began one year before his hospital admission and was treated by analgesics. The evolution was marked by swelling next to the tarsal navicular that gradually increased in size. Historically, the patient and his family had never been diagnosed with tuberculosis. The patient was not diabetic or immunosuppressed.
Physical examination revealed swelling of the tissue overlying the tarsal scaphoid. The area was firm and painful to touch. The patient had full foot mobility and no edema nor skin changes. There were no systemic signs of infection. X-ray showed marked navicular osteitis and tarso-metatarsal osteoarthritis with pronounced bone lysis and sequestration. The computerized tomography (CT) scan confirmed foot osteolysis (Fig. 1). Lung X-ray was normal.
Laboratory tests showed leukocytosis at 13,000/muL and CRP at 60 mg/l. Other laboratory tests were within normal limits. No tuberculin skin test was performed.
A biopsy of the bone lesion was performed. Bacteriological analysis of the bone fragment after Ziehl Nelseen staining was negative. However, the culture in the Bactec MGIT  960 liquid medium was positive after 10 days of incubation. The identification by molecular biology confirmed Mycobacterium tuberculosis sensitive to rifampin and isoniazid. Direct microbacterial study of sputum (three samples collected on consecutive days) and urine using Auramine and Ziehl Neelsen stains were negative for tuberculosis bacillus. The cultures were also negative.
Histopathological examination revealed an epithelioid and giant cell granulomatous inflammatory process with caseous necrosis consistent with tuberculosis. The patient was treated with a four drug anti-tuberculosis regimen (rifampin, isoniazid, pyrazinamide and ethambutol) for 4 months and the association of rifampicine and isoniazide for 10 months. Clinical improvement occurred after a period of 2 months as he reported decreased pain and swelling of foot and improvement in gait. CT scan 4 months after treatment still showed osteolysis of the tarsal bones (Fig. 2).