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10920 Kasilof Blvd

Anchorage, Alaska 99507



Phone: 907-346-2935


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What is a tubercle?

Tuberculosis (TB) is a bacterial disease caused by Mycobacterium tuberculosis.  

Scanning electron micrograph                                       TB in culture 

TB is transmitted through droplet nuclei, small particles of mucous produced when a person with TB coughs or sneezes.  These small microscopic particles can float in the air for hours. 

(Images courtesy of the CDC Public Health Image Collection)

If a person inhales particles, the particles may deposit in the alveoli, the small air sacs of the lungs, and the person becomes infected with TB. 

In persons with normal immune function, the inhaled bacteria provoke an immune response.  While the immune response commonly is unable to kill the bacteria, it is able to wall off the bacteria and able to prevent disease for long periods of time.  A tubercle is the name of the small inflammatory nodule that forms when the immune system builds a wall around the TB bacteria in the lungs. 

Infants and young children, and persons of all ages with weakened immune function due to HIV infection and other diseases,  are often unable to wall off the invading bacteria and progress rapidly to active TB disease.

Here is a chest radiograph on a baby, showing a large area of tuberculosis.  The baby’s father had active TB when the baby was born.  Within 2 months the baby was sick as well.  Fortunately the baby was diagnosed rapidly, treated with directly observed therapy (DOT) and cured.







Here’s a follow-up radiograph taken two years later: