Author(s): Miranda S. Bradley, MD, Carey Jackson, MD

Date Authored: March 7, 2020

Pulmonary tuberculosis (TB) is the most commonly thought of disease process associated with the bacteria Mycobacterium tuberculosis. Transmitted from person to person through the air, this pathogen usually does involve the lungs. However, TB can be present anywhere in the body if allowed time to spread. Disseminated tuberculin infection is typically a late stage finding and is becoming rare in the United States among US-born citizens. While TB was the leading cause of death in the US in the early 1900s, it is now primarily found in immigrant populations. Thus, it is still highly important that a clinician be able to consider and recognize TB as a potential cause of a patient’s ostensibly unassociated symptoms. 

tuberculosis under the microscope
Microscope image of mycobacterium tuberculosis. Photo: Sanofi Pasteur (cc license).

Tuberculosis can be a difficult disease to identify in certain situations. If someone is exposed to the bacteria during a time when their immune system is strong, they are usually able to fight off the pathogen, leading to the bacteria to become dormant in the body. If someone goes on to experience a time of immunocompromise later in life, the bacteria can reactivate and lead to disseminated disease if not properly treated. During this latent TB infection a person will not feel healthy and normal, they cannot spread the disease to others, but they will have a positive TB test (either ppd skin or blood test) if performed. 

If a person does not experience a time of immunocompromise in their lifetime after an initial infection with TB, it is unlikely they will ever be diagnosed with TB Disease or suffer symptoms from a reactivated infection. If they do suffer an illness that does lead to a decreased ability within the body to fight off infection, however, it is likely they will experience TB disease as well.

A Person with Latent TB Infection (LTBI)A Person with TB Disease
Usually has a TB skin test or blood test result indicating TB infectionUsually has a TB skin test or blood test result indicating TB infection
Has a normal chest x-ray and a negative sputum testMay have an abnormal chest x-ray, or positive sputum smear or culture
Has TB bacteria in his/her body that are alive, but inactiveHas active TB bacteria in his/her body
Does not feel sickUsually feels sick and may have symptoms such as coughing, fever and weight loss
Cannot spread TB bacteria to othersMay spread TB bacteria to others
Needs treatment for latent TB infection to prevent TB diseaseNeeds treatment for TB disease

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