Tuberculosis, also known simply as TB, comes in two forms: active TB and latent, or inactive, TB. Active TB primarily develops in the lungs in adults, but may also affect other areas of the body. In infants and small children, disseminated active tuberculosis is more common, which affects many body systems at once and may be fatal to the child.
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Someone with latent tuberculosis is infected with the bacteria Mycobacterium tuberculosis, or Mtb, but shows no symptoms and is not infectious. For people with active TB, symptoms can include chronic cough, coughing up blood, chest pain, fever, fatigue, weight loss, appetite loss, chills and night sweats. If tuberculosis affects certain organs, specific symptoms may occur, such as joint pain, leg paralysis, back pain, blood in the urine, painful urination, headaches or nausea. In disseminated tuberculosis, the whole body is affected and symptoms appear in various different organs and systems at the same time.
Latent tuberculosis occurs when an infected person develops an immune response that walls off the bacteria in the lungs using structures called granulomas. Granulomas can contain the bacteria and infected cells for long periods of time. If the bacteria inside the granulomas do not die, they can escape years later, bringing the disease into its active phase. In active tuberculosis, the released bacteria form pockets in the lungs and reproduce rapidly. If an active tuberculosis infection spreads into the blood, it can travel to different areas of the body, causing disseminated tuberculosis.
Only 10 percent of people with latent TB will develop active TB, explains the National Institute of Allergy and Infectious Diseases. Sometimes, the development of active TB takes years, but in most people the likelihood of developing active TB is highest in the first year after infection. Individuals with HIV are more likely to develop active tuberculosis
The only ways to diagnose an inactive tuberculosis infection are through a blood test or skin test. The tuberculin skin test, also called the Mantoux test, may produce false-positive or false-negative results, so follow-up tests are often given. Blood tests, which are more accurate than skin tests, measure the reaction of antibodies in the blood to the tuberculosis antigen. Active tuberculosis can be diagnosed by using a combination of skin or blood test and an observation of symptoms that indicate the presence of the disease. If necessary, chest x-rays or other scans may be used to look at the lungs for diagnosis. Lab tests on secretions from the stomach or lungs may also be performed.
Treatment for inactive tuberculosis is typically given in the form of isoniazid, or INH, a medication that must be taken for six to nine months to fully destroy the bacteria. An active infection is usually treated with a combination of the four drugs isoniazid, rifampin, pyrazinamide and ethambutol. These must be taken for a up to a year to be effective against the disease. In some cases, if the tuberculosis is a drug-resistant strain, treatment must continue daily for up to two years.