Overview of Clinical Tuberculosis

The clinical expression of infection with Mycobacterium tuberculosis is quite varied and depends on a number of identified factors. Immunization with bacillus of Calmette and Guerin (BCG) in persons with intact cell-mediated immunity minimizes the risk of early disseminated tuberculosis, especially in children. Systemic manifestations of the disease, including fever, malaise, and weight loss, are likely mediated by cytokines, especially tumor necrosis factor alpha (TNF-α). Weight loss, weakness, and malaise appear to be less common but are more difficult to quantify. Cough is the most common symptom of pulmonary tuberculosis. Tuberculosis that occurs relatively early in the course of HIV infection tends to have the typical radiographic findings described. Due to the frequency of extrapulmonary tuberculosis among HIV-infected patients, diagnostic specimens from any suspected site of disease should be examined for mycobacteria. Paravertebral or other para-articular abscesses may develop, with occasional formation of sinus tracts. Although weight-bearing joints are the most common sites for skeletal tuberculosis, any bone or joint may be involved. Meningitis is the most frequent form of central nervous system tuberculosis; solitary or multiple tuberculomas occur less commonly. The epidemiologic pattern of central nervous system tuberculosis is quite different from either pulmonary or other forms of extrapulmonary tuberculosis in that the peak incidence is in children in the zero-4-year age group, but an appreciable number of cases occur in adults. The chest pain may occasionally mimic angina but usually is described as being dull, aching, and often affected by position and by inspiration.