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For further information, see CMDT Part 9-13: Pulmonary Tuberculosis
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Essentials of Diagnosis
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Fatigue, weight loss, fever, night sweats, and productive cough
Risk factors for acquisition of infection: household exposure, incarceration, drug use, travel to an endemic area
Chest radiograph: pulmonary opacities, most often apical
Sputum smear positive for acid-fast bacilli or sputum culture positive for Mycobacterium tuberculosis
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General Considerations
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Primary infection
Occurs with inhalation of airborne droplets containing viable tubercle bacilli and subsequent lymphangitic and hematogenous spread before immunity develops
Up to one-third of new urban cases are from primary infection acquired by person-to-person transmission
Latent tuberculosis infection (LTBI)
Occurs when bacilli are contained within granulomata
Nontransmissible while latent, but may become active disease if the infected person's immune function becomes impaired
Drug-resistant strains of M tuberculosis are increasingly common worldwide, though rates in the US have fallen to less than 1.3%
Risk factors for drug resistance include
Immigration from countries with a high prevalence of drug-resistant tuberculosis
Close and prolonged contact with individuals with drug-resistant tuberculosis
Unsuccessful previous antituberculosis therapy
Patient nonadherence to such therapy
Resistance may be to single or multiple drugs
Drug-resistant tuberculosis is resistant to one first-line antituberculous drug, either isoniazid (INH) or rifampin (RIF)
Multidrug-resistant tuberculosis (MDR-TB) is resistant to INH and RIF, and possibly additional agents
Extensively drug-resistant tuberculosis (XDR-TB) is resistant to INH, RIF, fluoroquinolones and either aminoglycosides or capreomycin or both
Nonadherence is a major cause of treatment failure, disease transmission, and development of drug resistance
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Infects one-third of the world's population
In 2014, there were 9.6 million new cases of tuberculosis worldwide with 1.5 million people dying of the disease
In the United States, an estimated that 11 million people are infected with M tuberculosis and in 2014 there were 9421 active cases
Occurs disproportionately among malnourished, homeless, and marginally housed individuals
Risk factors for reactivation
Gastrectomy
Silicosis
Diabetes mellitus
HIV
Immunosuppressive drugs
Risk factors for drug resistance
Immigration from regions with drug-resistant tuberculosis
Close contact with patients infected with drug-resistant tuberculosis
Unsuccessful prior antituberculosis therapy
Patient noncompliance with such treatment
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Cough is the most common symptom
Blood-streaked sputum is common, frank hemoptysis is rare
Slowly progressive constitutional symptoms include malaise, anorexia, weight loss, fever, and night sweats
Patients appear chronically ill
Chest examination is nonspecific; post-tussive apical rales are classic
Atypical presentations are becoming more common, usually among the elderly and HIV-positive patients
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Differential Diagnosis
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Pneumonia
Lung abscess
Lung cancer or lymphoma
Mycobacterium avium complex (or other nontuberculous mycobacterial infection)
Sarcoidosis
Fungal infection, eg, histoplasmosis
Endocarditis
Silicosis or asbestosis
Nocardiosis
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