Extrapulmonary TB

Posted by e-Medical PPT Wednesday, September 19, 2012
Each year, tuberculosis (TB) results in the death of 3 million people globally.
In 2000-2020, an estimated 1 billion people will be infected, 200 million people will become sick, and 35 million will die from TB, if control is not strengthened.
Overall, one third of the world's population is infected with the TB bacillus, but not all infected individuals have clinical disease.

The Changing Face of TB
Disease patterns since have changed since the advent of human immunodeficiency virus (HIV) infection, with a higher incidence of disseminated and extrapulmonary disease now found
Extrapulmonary sites of infection commonly include lymph nodes, pleura, and osteoarticular areas, although any organ can be involved.
In general, extrapulmonary TB is more difficult to diagnose than pulmonary disease, often requiring invasive procedures to obtain diagnostic specimens and more sophisticated laboratory techniques than sputum microscopy.
As a result, extrapulmonary TB is often diagnosed on the basis of clinical experience which may lead to diagnostic errors, in either direction.

Extrapulmonary TB and HIV/AIDS
Extrapulmonary involvement can be seen in more than 50 percent of patients with concurrent AIDS and tuberculosis.
The risk of extrapulmonary tuberculosis and mycobacteremia increases with advancing immunosuppression.
In HIV-infected patients, TB tends to occur earlier than other AIDS-defining opportunistic infections when the CD4 cell count is in the range of 150-350 cells per microliter.
Unique features of AIDS-associated tuberculosis include:
extrapulmonary disease,
disseminated disease,
rapid progression,
visceral lymphadenopathy,
tissue abscesses, and
negative tuberculin skin test.
Response to antituberculous therapy is favorable and similar to that of patients without HIV infection, although adverse drug reactions occur more commonly in those with HIV infection.

Pleural Tuberculosis
In the United States, pleural tuberculosis accounts for about 5 percent of all tuberculosis cases.
Pleural tuberculosis often is an acute illness with cough, pleuritic chest pain, fever, or dyspnea.
Chest radiography typically reveals a small to moderate, unilateral pleural effusion; about 20 percent of patients have associated pulmonary lesions.
Computed tomography (CT) of the chest may show lymphadenopathy, pulmonary infiltrates, or cavitation not obvious on chest radiography
Pleural fluid
exudative with a lymphocyte predominance (i.e., more than 50 percent of white blood cells in more than 90 percent of effusions
Pleural fluid glucose and pH can be low or normal.
AFB smears of pleural fluid are seldom positive (5 percent of cases) unless the patient has tuberculous empyema.
Pleural fluid cultures for M. tuberculosis are positive in less than 40 percent of cases.
Pleural fluid PCR for M. tuberculosis has a sensitivity of 80 percent and a specificity of 100 percent.

The combined sensitivity of the analyses of pleural biopsy specimens (i.e., observation for caseating granulomas, AFB smear, and culture) is more than 90 percent.
Tuberculin skin test results are positive in two thirds of patients.
Biochemical markers such as adenosine deaminase, interferon gamma, and lysozyme in the pleural fluid can be useful.
In countries with a low prevalence of tuberculosis, such as the United States, a normal or low level of pleural fluid adenosine deaminase has a high negative predictive value and can be used to exclude tuberculous pleurisy.
Tuberculous pleurisy responds well to medical therapy, with resorption of pleural fluid in six to 12 weeks. The effusion may resolve without therapy, but tuberculosis later recurs.
Rare complications include bronchopleural fistula, empyema, and fibrothorax.

Peritoneal TB
Peritoneal tuberculosis, while currently the sixth most common site of extrapulmonary tuberculosis in the United States,is rarely found in isolation free of associated gastrointestinal involvement.
Peritoneal TB is a relatively uncommon manifestation of infection secondary to Mycobacterium tuberculosis and occurs either after reactivation of latent TB in the peritoneum or from active pulmonary or miliary TB with hematogenous spread.
It is often diagnosed late and has a high associated mortality
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