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INTRODUCTION

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Tuberculosis (TB) is the second most common cause of infectious disease deaths globally, with one-third of the world's population infected. Although active TB infection rates continue to decline in the United States, TB remains an important public health problem, particularly among immigrants whose active TB case rate is 12 times higher than the US-born population. Other risk factors include HIV infection; living or working in prison, shelters, and long-term care facilities; and alcohol/drug abuse. Transmission occurs by inhalation of droplet nuclei and may lead to active primary infection or latent disease (which may reactivate later). Identifying and treating high-risk patients for active and latent TB is key to ongoing TB control.

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CLINICAL FEATURES

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Primary TB

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Initial TB infection is usually asymptomatic in immune-competent adults, generally presenting with only a new positive reaction to TB skin testing (TST) or a new positive interferon gamma release assay (IGRA). These patients have normal chest radiographs (CXRs) and are presumed to have latent infections. When active primary TB does develop, symptoms often include fever, cough, weight loss, malaise, and chest pain. Some patients may present with active pneumonitis (which may be mistaken for community-acquired pneumonia) or extra-pulmonary disease.

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Children are more likely to present with active early disease, although the presenting symptoms may be subtle even when CXRs are abnormal. Presenting symptoms may include fever, cough, wheezing, poor feeding, and fatigue. TB meningitis and miliary TB are more common in children than adults.

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Immunocompromised patients are much more likely to develop rapidly progressive primary infections. All patients with active TB should be evaluated for immune-compromising conditions. Symptoms may be pulmonary (fever, cough, dyspnea, hemoptysis) or extrapulmonary, reflecting early hematogenous spread to the liver, bones, central nervous system, or other sites.

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Reactivation TB

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Latent TB infections will progress to active disease (i.e., reactivation TB) in 5% of cases within 2 years of primary infection; an additional 5% will reactivate over their lifetimes. Reactivation rates are higher in children, the elderly, persons with recent primary infection, those with immune compromise (in particular HIV), and those with chronic diseases such as diabetes and renal failure.

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Most patients with reactivation TB present subacutely with fever, malaise, weight loss, fatigue, and night sweats. Most patients with active TB will have pulmonary involvement and will develop productive coughs. Hemoptysis, pleuritic chest pain, and dyspnea may occur. Rales and rhonchi may be found, but the physical examination is not usually diagnostic.

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Extrapulmonary TB develops in up to 20% of active TB cases. Lymphadenitis, with painless enlargement and possible draining sinuses, is a common presentation. Patients may also present with symptomatic pleural effusion, pericarditis, peritonitis, or meningitis. Additional sites of reactivation TB after hematogenous spread include bones, joints, adrenals, GI tract, and GU tract. Extrapulmonary reactivation TB is more common and often more severe in young children ...

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