Art of Hypersensitivity Pneumonitis (HP)

Inflammatory response in the small airways attracts cellular interstitial infiltrates which surround the bronchiole. The diagram shows a bronchiole surrounded by an acute cellular inflammatory response
Ashley Davidoff MD TheCommonVein.net lungs-0722

 

Granuloma Impinges on the lumen of the centrilobular bronchiole The peri- bronchiole inflammation has receded in this subacute to chronic phase
Ashley Davidoff MD TheCommonVein.net lungs-0729
  • Granulomas around the bronchiole or arteriole
  • Occluding the Lumen of a Centrilobular Bronchiole
Granuloma occludes the lumen of the centrilobular bronchiole and the peri-bronchiole inflammation has receded in this subacute to chronic phase
Ashley Davidoff MD TheCommonVein.net lungs-0731

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    • Inflamed Alveoli
    Ashley Davidoff MD TheCommonvein.net lungs-0021
    • Early Events in the Pathophysiology of the ARDS
      The initial injury results in an acute severe inflammatory response consisting hyperemia , edema with migration initially of neutrophils in the first 6-24 hours followed by monocytes (24-48hours). The intra -alveolar macrophages are activated.
      Ashley Davidoff
      TheCommonVein.net

  • Result of Cellular Response
    The cells of the immune system release cytokines, chemotactic agents and proteases. Immune cells , macrophages and fibroblasts are attracted to the interstitium. Some of proinflammatory agents are toxic to the cell lining causing damage to the surfactant, type 1 pneumocytes and the capillary endothelium. There is progressive edema.
    Ashley Davidoff
    TheCommonVein.net

  • Result of Cellular Response and Associated Tissue Injury
    The damage to the endothelium of the capillary results in bleeding into the alveoli. The severe tissue damage and fluid exudation results in protein rich intra-alveolar fluid . The fibroblasts start to lay down collagen as part of the early repair process
    Ashley Davidoff
    TheCommonVein.net

  • Hyaline Membrane
    A hyaline membrane evolves covering the damaged surface of the alveolus. This impedes gas exchange
    Ashley Davidoff
    TheCommonVein.net