Skip to Main Content

INTRODUCTION

  • Tuberculosis (TB) is a communicable infectious disease caused by Mycobacterium tuberculosis. It can produce silent, latent infection, as well as progressive, active disease. Globally, 2 billion people are infected and roughly 1.5 million people die from TB each year.

PATHOPHYSIOLOGY AND ETIOLOGY

  • M. tuberculosis is transmitted from person to person by coughing or other activities that cause the organism to be aerosolized. Close contacts of TB patients are most likely to become infected.

  • Human immunodeficiency virus (HIV) is the most important risk factor for progressing to active TB, especially among people 25–44 years of age. An HIV-infected individual with TB infection is over 100-fold more likely to develop active disease than an HIV-seronegative patient.

  • Approximately 90% of patients who experience primary disease have no further clinical manifestations other than a positive skin test either alone or in combination with radiographic evidence of stable granulomas. Tissue necrosis and calcification of the originally infected site and regional lymph nodes may occur, resulting in the formation of a radiodense area referred to as a Ghon complex.

  • Approximately 5% of patients (usually children, the elderly, or the immunocompromised) experience progressive primary disease at the site of the primary infection (usually the lower lobes) and frequently by dissemination, leading to meningitis and often to involvement of the upper lobes of the lung as well.

  • Approximately 10% of patients develop reactivation disease, which arises subsequent to the hematogenous spread of the organism. In the United States, most cases of TB are believed to result from reactivation.

  • Occasionally, a massive inoculum of organisms may be introduced into the bloodstream, causing widely disseminated disease and granuloma formation known as miliary TB.

CLINICAL PRESENTATION AND DIAGNOSIS

  • Patients with TB typically present with cough, weight loss, fatigue, fever, and night sweats. Symptom onset may be gradual.

  • Frank hemoptysis usually occurs late in the course of disease but may present earlier.

  • On physical examination, the patient is usually thin with evidence or recent weight loss. Dullness to chest percussion, rales, and increased vocal fremitus are often present, but a normal lung examination is common compared to the degree of radiological lung involvement.

  • The white blood cell (WBC) count is usually moderately elevated with lymphocyte predominance. A high platelet count (thrombocytosis) and mild-to-moderate anemia are common.

  • Sputum smear is done to detect mycobacteria. A fiber-optic bronchoscopy is performed if sputum tests are inconclusive and suspicion is high.

  • Chest radiograph shows patchy or nodular infiltrates in the apical areas of the upper lobes or the superior segment of the lower lobes. There may be cavitation that shows air–fluid levels as the infection progresses.

  • Clinical features associated with extrapulmonary TB vary depending on the organ system(s) involved but typically consist of slowly progressive decline of organ function with low-grade fever and other constitutional symptoms.

  • Patients with HIV may have atypical presentation. HIV-positive patients are less likely ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.