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Chapter 14 : Pulmonary Tuberculosis
Category: Clinical Microbiology; Bacterial Pathogenesis
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Pulmonary tuberculosis frequently develops without any striking clinical evidence of disease. The chest radiography is the single most useful study for suggesting the diagnosis of TB. In the past, primary TB was seen mostly in children and reactivation TB in adults. Computed tomography (CT) scans allow practitioners to examine both the pulmonary parenchyma and the lymph nodes in greater detail than can be done with plain chest X ray alone. For patients with HIV infection but without the manifestations of AIDS, the tuberculin skin test is positive in 50 to 80% of patients with TB. One meta-analysis of 12 studies of TB found that the elderly were less likely to have symptoms such as fever, sweating, hemoptysis, and cavitary lung disease. They were more likely to have dyspnea and significant comorbidities. In this study, the only difference seen in radiographic patterns between young adults and the elderly was an increased incidence of miliary disease in the older population. In a prospective cohort study of patients diagnosed with TB, it was found that the older group had more toxicity from the TB therapy (22% versus 9%) and a greater 30-day mortality rate (18% versus 2%). Inhibition of Tumor necrosis factor alpha (TNF-α); is now used for the treatment of several diseases, including rheumatoid arthritis, Crohn’s disease, juvenile rheumatoid arthritis, ankylosing spondylitis, and psoriatric arthritis. Tuberculous pleural effusions are usually due to rupture of a subpleural focus of TB. This release is then followed by a T-cell-mediated hypersensitivity response with marked inflammation.
Key Concept Ranking
- Tumor Necrosis Factor alpha
Primary TB in an adult. Shown is a right lower-lobe infiltrate with bilateral hilar adenopathy.
Left upper-lobe TB. Shown is a typical fibronodular pattern of reactivation TB with linear densities extending to the left hilum.
Late changes of upper-lobe TB. (A) Posterior-anterior chest radiograph with volume loss of the right upper lobe is indicated by the elevated minor fissure. Small cavities are not clearly seen, but there is endobronchial spread to the superior segment of the right lower lobe, suggesting cavitary formation. (B) A computerized axial tomography scan of the same patient that clearly demonstrates extensive bilateral cavitary disease.
Miliary TB. (A) Characteristic diffuse small nodules are seen in the posterior-anterior radiograph. (B) A computerized axial tomography scan of the lung in the same subject demonstrates the diffuse small nodular disease.
Tuberculous empyema. Shown are posterior-anterior (A) and lateral (B) chest radiographs demonstrating a left lower-lobe effusion.
Increased susceptibility to TB
Clinical symptoms of patients presenting with active TB a
Criteria for activity in pulmonary TB