A contagious bacterial infection caused by the bacterium Mycobacterium tuberculosis , which has spread to other organs of the body by the blood or lymph system .

Alternative Names

Miliary tuberculosis; Tuberculosis - disseminated; Extrapulmonary tuberculosis

Causes, incidence, and risk factors

The infection can develop after inhaling droplets sprayed into the air as 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. Primary infection is usually asymptomatic . In the United States, 95% of individuals will have healing of their primary tuberculous lesions with no further evidence of disease. Disseminated disease develops in the minority 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 and the elderly 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, bronchus, cervical lymph nodes, bones and joints, organs of the male or female urinary and reproductive (genitourinary) system, eye, stomach, 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. Hispanics, Native Americans, and blacks are at higher risk for developing the disease. An increased incidence of TB has been seen recently in the United States. Factors that may be causing this increase is tuberculous infection in people with AIDS and HIV infection , and increasing number of homeless people. Another factor 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. Disseminated TB is more common in AIDS patients. 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).

Signs and tests

Enlarged lymph nodes , enlarged liver , and enlarged spleen are revealed with physical exam. Tests:

chest X-ray

sputum cultures

tuberculin skin test

bronchoscopy

for

biopsy or culture

open lung biopsy

pleural biopsy

biopsies

and cultures of affected organs or tissues

retinal lesions revealed with fundoscopy

This disease may also alter the results of the following tests:

peripheral smear

serum calcium (may be elevated)

mycobacterial culture of bone marrow

Treatment

The goal of treatment is to cure the infection with antitubercular drugs. These drugs include: ethionamide, para-aminosalicylic acid (PAS), pyrazinamide, isoniazid (INH), rifampin, ethambutol, and streptomycin. Daily oral doses are continued for 1 year or longer.

For atypical tuberculosis infections, or drug-resistant strains, other drugs may be indicated to treat the infection. A minimum of three drugs are started for treatment. Hospitalization is indicated to prevent the spread of the disease to others until the infectious period is over, usually 2 to 4 weeks after the start of therapy. Normal activity can be continued after the infectious period.

Expectations (prognosis)

Most disseminated forms of tuberculosis respond well to treatment.

Complications

All medications used to treat TB have some toxicity. Rifampin and isoniazid may both cause a non-infectious hepatitis. Rifampin may also cause an orange or brown coloration of tears and urine, and can stain contact lenses and undergarments. Other complications include:

drug resistance

relapse of the disease

tuberculous

meningitis

respiratory

failure

adult respiratory distress syndrome

(

ARDS )

Calling your health care provider

Call your health care provider if known or suspected exposure to tuberculosis has occurred. All forms of tuberculosis require prompt treatment.

Prevention

Vaccination BCG for tuberculin-negative persons exposed to persons with untreated TB is given in some situations, but its effectiveness is under dispute. It is rarely used in the U.S. but is often used abroad, in countries with higher rates of tuberculosis.