What is primary tuberculosis?
Primary Tuberculosis (Primary TB) Primary tuberculosis is the initial infection caused by Mycobacterium tuberculosis in a person who has never been previously exposed to the bacterium. It typically occurs in children or young adults but can also affect people of any age. Key Features of Primary TB Aspect Details Cause First exposure to M. tuberculosis Immunity Host has no pre-existing immunity Common Site Mid/lower zones of the lungs (usually subpleural) Characteristic Lesion Ghon focus (initial lesion in lung parenchyma) Lymph Node Involvement Ghon complex = Ghon focus + involved hilar lymph nodes Immune Response Cell-mediated immunity develops over 2–3 weeks Outcome Usually heals with fibrosis and calcification; may become latent Pathogenesis of Primary TB Inhalation of bacilli → reaches alveoli Bacilli are engulfed by alveolar macrophages Initiates granulomatous inflammation Formation of Ghon focus (small area of caseatio...