Skeletal tuberculosis (TB) refers to TB involvement of the bones and/or joints. It is an ancient disease; features of spinal TB have been identified in Egyptian mummies dating back to 9000 BC [1,2], and analysis of 483 pre-Columbian skeletons in Chile showed lesions consistent with bony tuberculosis in 2 percent of cases . Subsequently, molecular studies have established the presence of Mycobacterium tuberculosis complex DNA in ancient bony specimens [2,4].
Clinical issues related to skeletal TB will be reviewed here. Other aspects of TB are discussed separately (see related topics).
Skeletal TB accounts for 10 to 35 percent of cases of extrapulmonary tuberculosis and, overall, for almost 2 percent of all TB cases [5-9]. Reported rates of extrapulmonary TB are higher among immigrants from endemic areas to developed countries; this may be due in part to immigration screening procedures for pulmonary TB. One retrospective review of skeletal TB between 1980 and 1994 in France noted 103 cases of spinal TB; 68 percent of patients were foreign-born, the majority from Africa . The proportion of skeletal TB among HIV-infected individuals is comparable to the proportion of skeletal TB among HIV–uninfected individuals [11,12].
The most common form of skeletal TB is Pott disease, a disease of the spine; this entity comprises approximately half of musculoskeletal TB cases. The next most common form of musculoskeletal TB is tuberculous arthritis, followed in frequency by extraspinal tuberculous osteomyelitis .
During primary M. tuberculosis infection, bacillemia may lead to seeding of organisms in bone and/or synovial tissue. In most cases, small foci of infection are confined by local immune processes and infection is subclinical. Following primary infection, reactivating foci may be contained by the cellular immune response. CD4 and CD8 lymphocytes play important roles, as does interferon gamma . Reactivation of infection with progression to clinically apparent disease may occur when local immune defenses fail, as in the setting of malnutrition, advancing age, HIV infection, or renal failure .