Tuberculosis occurs most commonly in the lungs, but may appear in any organ, the kidney, bones, lymph nodes, ect. In developed countries tuberculosis is spread by the inhalation of organisms which may float in the air for several hours. Tuberculosis in children typically appears in the apices of one or both lungs as “Simon foci”. Here it may lie dormant for many years and when active, the infection spreads to the hilar lymph nodes.
Tuberculin skin test: A small amount of TB protein is put under the top layer of skin on the forearm, A positive reaction to the tuberculin protein (antigen) will cause a red bump within 2 days, indicating exposure to the tuberculosis bacteria.