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Primary pulmonary tuberculosis

Clinical data

  • There is no clinical history recorded.

Post mortem pathology

  • The specimen consists of the hilum and lungs of an infant. 
  • In the lower lobe of the left lung on its medial aspect there is a caseous focus, the Ghon focus. 
  • There is prominent caseation of the draining tracheobronchial and mediastinal nodes.
  • The Ghon focus in the lung together with the involved hilar nodes form the ‘primary complex’ or Ghon complex.

Lower lobe of left lung showing Ghon focus.

  • The Ghon focus typically occurs in lower part of an upper lobe or upper part of a lower lobe, and is usually subpleural.
  • The subpleural lesion quite often causes a small pleural effusion. 
  • The immune response to TB infection is primarily cell mediated and comes at the cost of “hypersensitivity” to mycobacterial antigens which causes caseating granulomas and ultimately tissue destruction.

Microscopy of a tubercle in lung

Microscopy, two more granulomas, at a more advanced stage.

Further developments

  • Most cases of primary tuberculosis heal at this stage, leaving a small fibrocalcific scar in the lung, sometimes visible on x-ray. Viable organisms may remain dormant in this lesion for decades.
  • In children (< 2 years) the primary complex may not be contained. Rupture into a bronchus can cause tuberculous bronchopneumonia or haematogenous dissemination can cause miliary tuberculosis.
  • In some persons (usually immunocompromised) primary tuberculosis may immediately progress as “progressive primary tuberculosis”;  in the lungs this may be radiologically indistinguishable from reactivation tuberculosis .  


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