Musculoskeletal brucellosis.

Brucellosis is a zoonosis of worldwide distribution caused by small gram-negative nonencapsulated coccobacilli of the genus Brucella. It is characterized by a granulomatous reaction in the reticuloendothelial system. Because it affects several organs and tissues, it may have various clinical manifestations. Musculoskeletal involvement is one of the most common locations, and the frequency of bone and joint (osteoarticular) involvement of brucellosis varies between 10% and 85%. Osteoarticular involvement includes spondylitis, sacroiliitis, osteomyelitis, peripheral arthritis, bursitis, and tenosynovitis. The most common osteoarticular finding in children is monoarticular arthritis, mostly located in the knees and hips; whereas in adults, sacroiliitis is the most frequent. Imaging studies, including radiography, computed tomography (CT), magnetic resonance (MR) imaging, and bone scintigraphy, have been used for diagnosis. Radiography is limited to evaluating the focal form of spinal brucellosis and advanced disease at the joints. CT and bone scintigraphy have limited value because of their inadequate soft tissue resolution. MR imaging is the method of choice to assess the extent of disease and follow up the treatment response. However, MR imaging has a low specificity to predict the exact cause of an osteoarticular lesion, and in case of arthralgia or symptoms of osteomyelitis or spondylodiscitis, the index of suspicion should be high in regions where the disease is endemic.