Types of Tuberculosis

Tuberculosis (TB) is a disease caused by a bacterium called Mycobacterium tuberculosis, and can manifest in many different areas of the body. TB can be both active (resulting in disease) and inactive (asymptomatic infection). According to the Centers for Disease Control (CDC), a third of the world population is infected with tuberculosis, with 9 million becoming sick because of the disease. TB kills 2 million people annually, and in 2008, nearly 13,000 people developed TB in the United States.

Inactive (Latent) Tuberculosis

• Inactive TB implies that the host is infected with the bacterium that causes TB, but is asymptomatic. In people with inactive TB, the body's immune system effectively fought the infection and renders it inactive by surrounding the bacterial colonies and individual bacteria with scar tissue. This form of TB has no symptoms and cannot be spread to other people. These little balls of scar tissue are called granulomas, are sometimes visible under an x-ray, and can in some cases be mistaken for cancer.

Active Tuberculosis

• Active TB implies infection of a host with the bacterium that causes TB coupled with an immune system that is unsuccessful in eliminating or corralling the pathogens. This leads to an active infection that is both dangerous and debilitating. Unlike inactive TB, active TB is easily spread amongst people, generally by coughing it into the air, where others can breathe it in and become infected themselves. When symptoms of active TB are present, health officials may institute a quarantine of the infected person or people to prevent the spread of the disease. Active tuberculosis can be divided into three different types: primary, secondary, and disseminated.

Primary (Pulmonary) Tuberculosis

• By far the most common manifestation of active TB is in the lungs, called pulmonary TB (and also sometimes called consumption). Because the bacterium that causes TB needs oxygen to survive, the oxygen-rich air sacs of the lungs are an ideal breeding ground. Symptoms of an infection in the lungs by TB include a chronic cough, coughing up blood, along with chest pain or pain associated with breathing or coughing. Pulmonary TB causes severe pneumonia, and if untreated, can very easily result in death. As an active form of TB, it is highly contagious.

Secondary (Reactive) Tuberculosis

• Secondary TB is a form of active TB that stems from an inactive infection. When the body's immune system is weakened for any reason, the granulomas encasing the bacteria that cause TB are also weakened, and the encapsulated bacteria can break out of their scar-tissue prisons. Once out, they are free to cause an active TB infection of the lungs or elsewhere, although generally, the upper lungs are the most commonly effected area of the body.

Disseminated Tuberculosis

• The most rarest form of active TB, disseminated TB occurs when a TB infection (whether primary or secondary) spreads to various other systems throughout the body. Disseminated TB has been found to spread to and affect the bones (especially the spine, hip and knee), the genital tract in women, the urinary tract, the central nervous system (where it infects the cerebrospinal fluid), the gastrointestinal tract, the adrenal glands, the skin of the neck (called scrofula) and in the heart. The symptoms of disseminated TB vary widely and depend upon which system has become infected with the disease.