Tuberculosis
Basics
Description
- Active tuberculosis (TB) infection caused by Mycobacterium tuberculosis
- Primary infection or reactivation of latent infection. Risk increases with immunosuppression: highest risk first 2 years after infection. Reactivation risk increases with comorbid disease (e.g., HIV, diabetes).
- Well-described forms: pulmonary (85%), miliary (disseminated), meningeal, abdominal, lymphadenitis (scrofula)
- Usually acquired by inhalation of airborne bacilli from an individual with active TB. Bacilli multiply in alveoli and spread via macrophages, lymphatics, and blood. Outcomes include: eradication (tissue hypersensitivity stops infection; primary TB; latent TB (LTBI).
Epidemiology
Incidence
- Worldwide (2021): an estimated 10.6 million people equivalent to 134/100,000
- 7% of cases involve people living with HIV. Most cases in Southeast Asia and Africa.
- United States (2022): 8,300 (2.5/100,000); 71% of U.S. cases were in persons born outside of the United States. Following a 10-year decline, TB case rates rose slightly in 2022.
Prevalence
- Worldwide (2020): World Health Organization estimates 9.9 million new cases of TB in 2020.
- Mortality
- Worldwide (2021): 1.6 million deaths due to TB; 13th leading cause of death worldwide
Etiology and Pathophysiology
- M. tuberculosis, Mycobacterium bovis, or Mycobacterium africanum are causative organisms.
- Spread by aerosol droplets and reach alveolar space. Alveolar macrophages ingest and migrate.
- Cell-mediated response by activated T lymphocytes and macrophages forms a granuloma (“tubercle”) that limits bacterial replication. If bacterial replication continues, the tubercle grows with spread to regional lymph nodes. An expanding tubercle within the lung parenchyma combined with regional lymph node enlargement is called a Ranke complex.
- As the infection is contained, destruction of the macrophages produces early “solid necrosis.” In 2 to 3 weeks, “caseous necrosis” develops and LTBI ensues. In the immunocompetent, granuloma undergoes “fibrosis” and calcification. In the immunocompromised, primary progressive TB develops. Cavitary lesions may form.
Risk Factors
- For latent infection: homeless, correctional facilities, close contact with infected person, living in areas with high incidence of active TB, health care workers; medically underserved, low income, substance abuse
- For development of disease once infected: renal failure; lymphoma; silicosis; diabetes; cancer of head, neck, or lung; children aged <5 years old; malnutrition; systemic corticosteroids; HIV; immunosuppressive drugs; IV drug abuse, alcohol abuse, cigarette smokers; <2 years since infection with M. tuberculosis; <90% of ideal body weight
General Prevention
- Screen for and treat LTBI. Report active TB to health department; test and treat all close contacts. Without treatment, LTBI will progress to active TB disease in 5–10% of affected people.
- Bacillus Calmette-Guérin (BCG) vaccine: used primarily in endemic countries; BCG is not recommended in United States for high-risk children with negative PPD and ongoing exposure.
Commonly Associated Conditions
Immunosuppression; HIV coinfection; malignancy
There's more to see -- the rest of this topic is available only to subscribers.
Citation
Domino, Frank J., et al., editors. "Tuberculosis." 5-Minute Clinical Consult, 33rd ed., Wolters Kluwer, 2025. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688539/all/Tuberculosis.
Tuberculosis. In: Domino FJF, Baldor RAR, Golding JJ, et al, eds. 5-Minute Clinical Consult. Wolters Kluwer; 2025. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688539/all/Tuberculosis. Accessed October 13, 2024.
Tuberculosis. (2025). In Domino, F. J., Baldor, R. A., Golding, J., & Stephens, M. B. (Eds.), 5-Minute Clinical Consult (33rd ed.). Wolters Kluwer. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688539/all/Tuberculosis
Tuberculosis [Internet]. In: Domino FJF, Baldor RAR, Golding JJ, Stephens MBM, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2025. [cited 2024 October 13]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688539/all/Tuberculosis.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC
T1 - Tuberculosis
ID - 1688539
ED - Domino,Frank J,
ED - Baldor,Robert A,
ED - Golding,Jeremy,
ED - Stephens,Mark B,
BT - 5-Minute Clinical Consult, Updating
UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688539/all/Tuberculosis
PB - Wolters Kluwer
ET - 33
DB - Medicine Central
DP - Unbound Medicine
ER -