A 30 year old veterinarian presents with nocturnal pain in the right lower back for 2 weeks, in association with fatigability, night sweats, and fever with chills at night.

He migrated from Brazil to the United States 3 weeks ago. He had been working in the same occupation in his home country.

His medical history is unremarkable. There is no history of contact with tuberculosis. He has a single stable sexual partner. There is no family history of spondyloarthropathies.

His ESR is found to be 20 mm/1h. Radiographs of the pelvis are found to be normal. A tuberculin test was performed in view of the symptoms, but is nonreactive.

Prior to migration, he was tested for HIV and found to be negative.