Tuberculosis (TB) is an acute or chronic infection characterized by pulmonary infiltrates and by the formation of granulomas with caseation, fibrosis, and cavitation. The American Lung Association estimates that active disease has increased by more than 20% in the past 5 years.
The disease is twice as common in men as in women and four times as common in nonwhites as in whites. Incidence is highest in people who live in crowded, poorly ventilated, unsanitary conditions, such as prisons, tenement houses, and homeless shelters. The typical newly diagnosed patient with TB is a single, homeless, nonwhite man. With proper treatment, the prognosis is usually excellent.
TB results from exposure to Mycobacterium tuberculosis and, sometimes, other strains of mycobacteria. Transmission occurs when an infected person coughs or sneezes, spreading infected droplets.
The following are at-risk populations that incur a high incidence of TB with presenting symptoms:
Signs and Symptoms
Symptoms of pulmonary TB include fever, fatigue, loss of appetite and weight, night sweats and persistent cough. Phlegm coughed up may be streaked with blood. Tuberculous pleurisy (affecting the membranes around the lungs) leads to an accumulation of fluid in the pleural cavity (the normally very small space between the membranes) and partial collapse of the lung.
Rarely, the TB in the lung erodes an artery, causing dangerous bleeding into the lung. TB may then spread widely throughout the body via the bloodstream. Meningitis is another dangerous complication.
Several of the following tests may be necessary to distinguish TB from other diseases that may mimic it, such as lung carcinoma, lung abscess, pneumoconiosis, and bronchiectasis.
Chest X-rays show nodular lesions, patchy infiltrates (mainly in upper lobes), cavity formation, scar tissue, and calcium deposits. They may not help distinguish between active and inactive TB.
A tuberculin skin test reveals that the patient has been infected with TB at some point, but it doesn't indicate active disease. In this test, intermediate-strength purified protein derivative or 5 tuberculin units (0.1 ml) are injected intradermally on the forearm and read in 48 to 72 hours. A positive reaction (greater than or equal to a 10-mm induration) develops within 2 to 10 weeks after infection with the tubercle bacillus in both active and inactive TB.
Stains and cultures of sputum, cerebrospinal fluid, urine, drainage from abscess, or pleural fluid show heat-sensitive, nonmotile, aerobic. acid-fast bacilli.
Computed tomography scans or magnetic resonance imaging allow the evaluation of lung damage or confirm a difficult diagnosis.
Bronchoscopy may be performed if the patient can't produce an adequate sputum specimen.
Antitubercular therapy with daily oral doses of isoniazid, rifampin, and pyrazinamide (with ethambutol added in some cases) for at least 6 months usually cures TB. After 2 to 4 weeks, the disease is no longer infectious and the patient can resume normal activities while continuing to take medication.
The patient with atypical mycobacterial disease or drug-resistant TB may require second-line drugs, such as capreomycin, streptomycin, paraaminosalicylic acid, pyrazinamide, and cycloserine.
Treatment to prevent TB in a single person aims to kill walled-up germs that are doing no damage right now, but could break out years from now and become active.
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