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Disseminated tuberculosis

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Definition:

Tuberculosis (TB) is a contagious bacterial infection caused by the bacterium Mycobacterium tuberculosis. It is "disseminated" if it has spread from the lungs to other organs of the body by the blood or lymph system . See also tuberculosis - pulmonary .

Alternative Names:

Miliary tuberculosis; Tuberculosis - disseminated; Extrapulmonary tuberculosis

Causes, incidence, and risk factors:

Infection can develop after inhaling droplets sprayed into the air from a cough or sneeze by someone infected with Mycobacterium tuberculosis . The disease is characterized by the development of granulomas (granular tumors) in the infected tissues.

The usual site of the disease is the lungs, but other organs may be involved. The primary infection usually has no symptoms. In the U.S., 95% of individuals the primary tuberculous lesions will heal and there will be no further evidence of disease. Disseminated disease develops in the minority of infected individuals whose immune systems do not successfully heal the primary infection.

The disease may occur within weeks after the primary infection, or may lie dormant for years before causing illness. Infants, the elderly, and those infected with HIV are at higher risk for rapid progression to disease, because of their weaker immune systems.

In disseminated disease, organs and tissues affected can include: the lining of the heart (pericardium), lining of the abdominal cavity (peritoneum), larynx (voice box), bronchus, cervical lymph nodes, bones and joints, organs of the male or female urinary and reproductive (genitourinary) system, eye, stomach, small bowel, lining of the brain and spinal cord (meninges), and skin.

The risk of contracting TB increases with the frequency of contact with people who have the disease, in crowded or unsanitary living conditions, and with poor nutrition.

An increased incidence of TB has been seen recently in the U.S. Factors that may be causing this increase is tuberculous infection in people with AIDS and HIV infection , and increasing numbers of homeless people. Another matter of concern is the development of drug-resistant strains of TB.

Incomplete treatment of TB infections (such as not taking medications for the prescribed length of time) can contribute to the proliferation of drug-resistant strains of bacteria.

About half of AIDS patients with a CD4 count less than 200 who develop TB will have disseminated disease (not localized disease, as in pulmonary tuberculosis).

• Review Date: 2/13/2006
• Reviewed By: Monica Gandhi, M.D., M.P.H., Assistant Professor, Division of Infectious Diseases, UCSF, San Francisco, CA. Review provided by VeriMed Healthcare Network.

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