Brucellar Bone and Joint Infection

Osteoarticular brucellosis (OAB) usually occurs as sacroiliitis, spondylitis, or peripheral arthritis. Although OAB is the most frequent complication of human brucellosis, tissue specimens of OAB are rarely histologically examined, because in contrary to pyogenic and tuberculosis infections, biopsy is rarely necessary to confirm the diagnosis of OAB. Tissue diagnosis in patients with OAB is generally used, when other causes are suspected particularly in the presence of paraspinal abscess or neurological deficits. The histological diagnosis of OAB lacks pathognomonic features. Microscopically, OAB shows a spectrum of lesions ranging from nonspecific forms mimicking pyogenic infection to granulomatous forms mimicking tuberculosis and other granulomatous diseases. This broad histological spectrum and the rareness of histological specimens in routine practice make the histological diagnosis of OAB challenging. The definitive diagnosis of OAB requires combination of clinical context, radiological features, and laboratory tests, mainly serological tests for Brucella agglutinin. The role of histological examination is mainly to rule out other infectious process, particularly tuberculosis and tumor process. Although not used in routine practice for the diagnosis of OAB, ancillary techniques (immunohistochemistry and molecular methods), with validated protocols, may be helpful to establish the definitive diagnosis of OAB in formalin-fixed specimens.