Tuberculosis

What is tuberculosis?

Tuberculosis (TB) is a contagious respiratory disease caused by the organism Mycobacterium tuberculosis. Infection is spread when a person with TB disease coughs, sneezes, laughs, or spits; droplets containing the bacteria are spread into the air and are breathed in by another person. Once propelled into the air, the bacteria can remain suspended for hours. After inhalation, the bacteria settle in the lungs and cause a local infection.

If a person's immune system is intact, tuberculosis infection will stay localized and will usually not spread. The immune system normally stops TB infection in its early stages by "walling off" the bacteria. The isolated bacteria become inactive or dormant but remain alive. If an infected person's immunity becomes weakened, the bacteria may break out and multiply.

The resultant infection is called tuberculosis disease. This stage can be very debilitating. It can cause massive tissue damage to the lungs, and occasionally spreads to other parts of the body such as the kidneys or spine. If left untreated, TB disease can be fatal.

How is it diagnosed?

History is of contact with someone who has active tuberculosis, or has traveled to an area where the disease is prevalent. The majority of people will have no symptoms unless TB disease develops. Characteristic symptoms then include a productive cough for more than two weeks, chest pain, fatigue, loss of appetite and weight loss, fever, chills, and night sweats; blood in the sputum is seen relatively infrequently.

Physical exam can be quite unremarkable the lungs may sound normal, temperature may or may not be elevated; enlarged lymph nodes can be noted in the neck. Someone with advanced disease, however, will look chronically ill and with muscle wasting ("consumption").

Tests: TB infection is diagnosed by a positive skin test; but this test can be negative with a recent infection (less than two to three months previously) or if immunocompromised (HIV), so should be repeated if a person has a recent exposure to TB.

If an individual shows signs of TB disease and reacts positively in the skin test, other tests can confirm the diagnosis. The TB organism can be identified from a sputum sample by microscopic examination and by a culture; this may take weeks to get back. A chest x-ray can show characteristic abnormalities.

If advanced TB disease is diagnosed in the lungs, blood tests and urine samples may be used to look for spread and impairment of the liver and other tissues. Blood tests may show signs of chronic illness and nutritional deficiencies, like anemia and low proteins.

How is tuberculosis treated?

Tuberculosis disease can be cured with a combination of antibiotics; since active lung disease is infectious, the individual should be kept in isolation for two to three weeks.

Effective treatment requires at least six months of uninterrupted medication, sometimes continuing for years. If medication fails, surgery may be needed to remove diseased tissue and pockets of bacterial infection. Treatment of tuberculosis also involves screening exposed people who may have become infected.

Medications

Antitubercular drugs, usually for 9-12 months. Several types are given at the same time to avoid bacterial resistance to the drugs. Tuberculosis has become increasingly resistant to traditional antibiotics.

What might complicate it?

Misdiagnosis and poor patient compliance with the long course of medication are the main reasons for treatment failure. The development of antibiotic resistance will complicate and prolong the therapy. For this reason, treatment of all individuals should be monitored closely.

Tuberculosis disease may be activated or reactivated by a medical condition that weakens the immune system, such as leukemia, lymphoma, cancer, steroid therapy, radiation treatment, and infection with certain viruses (including HIV), bacteria, or fungi.

Some individuals exhibit adverse side effects from the antibiotic treatment. Treatment may need to be altered if the side effects include nausea, vomiting, yellowish skin or eyes, fever for more than three days, abdominal pain, skin rash, tingling fingers or toes, bleeding abnormalities, numbness, easy bruising or ringing in the ears (tinnitus).

Infrequently, tuberculosis will spread to the kidneys, spine, or liver (disseminated or miliary TB).

Predicted outcome

The prognosis for treated TB infection is good, for an otherwise healthy individual. Antibiotic therapy can cure the disease, leaving little or no residual damage to the lungs.

Once the infection progresses to become TB disease, the prognosis is less certain. The great majority of cases can be cured, if the organism is not drug-resistant and the individual complies with the long drug treatment schedule. But there can be residual damage to the lungs and occasionally other tissues, even after effective antibiotic therapy. The extent of damage depends upon the status of the immune system, the effectiveness of antibiotic therapy, and the severity of disease at the start of treatment.

If left untreated, half of those with TB disease will die; another 25% will have chronic TB with a cough.

Alternatives

A systemic fungus infection, sarcoidosis, or lung cancer can have clinical similarities with TB, as can other bacterial, fungal and viral infections of the lung. Infection with related but non-tubercular mycobacterial species, or HIV infections, can result in misleading skin test results. TB may be misdiagnosed as a "fever of unknown origin."

Appropriate specialists

Endocrinologist and internist.

Last updated 27 May 2015