Disseminated tuberculosis (TB) is a contagious bacterial infection that has spread from the lungs to other parts of the body through the blood or lymph system.

See also: Tuberculosis - pulmonary

Tuberculosis (TB) infection can develop after inhaling droplets sprayed into the air from a cough or sneeze by someone infected with the Mycobacterium tuberculosis bacteria. Small areas of infection, called granulomas (granular tumors), develop in the lungs.

The usual site of tuberculosis is the lungs, but other organs can be involved. In the U.S., most people with primary tuberculous get better and have no further evidence of disease. Disseminated disease develops in the small number of infected people whose immune systems do not successfully contain the primary infection.

Disseminated disease can occur within weeks after the primary infection, or may lie dormant for years before causing illness. Infants, the elderly, those infected with HIV. and those who take immune-suppressing medications are at higher risk for the disease worsening, because of their weaker immune systems.

In disseminated disease, organs and tissues affected can include:

• Bones and joints
• Bronchus
• Cervical lymph nodes
• Eye
• Larynx (voice box)
• Lining of the abdominal cavity (peritoneum)
• Lining of the brain and spinal cord (meninges)
• Lining of the heart (pericardium)
• Organs of the male or female urinary and reproductive systems
• Skin
• Small bowel
• Stomach

The risk of catching TB increases when you are in contact with people who have the disease, if you live in crowded or unsanitary conditions, and if you have poor nutrition.

Recently, TB has been seen more often in the U.S. Factors that may be causing this increase are tuberculosis infections in people with AIDS and HIV, 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 development 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).