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Pathology - Hypersensitivity pneumonitis
Definition: An interstitial lung disease resulting from an immunological response to inhaled antigens. Synonyms include extrinsic allergic alveolitis. Various versions of the disease are referred to by numerous alternative names, such as farmer’s lung, humidifier lung, maple bark stripper’s lung, mushroom worker’s lung, pigeon breeder’s lung, and bird fancier’s lung, among others.
Epidemiology: Rare occurrence.
Aetiology: • Thermophilic bacteria (found in moldy hay, compost, and air conditioning ducts), • Fungi (present in moldy maple bark, barley, or wood dust). • Avian proteins (excrement and plumage of birds).
Pathogenesis: Inhaled antigens provoke an aberrant immune response in the pulmonary system. • Comprises a synthesis of antibody-mediated (type 2), immune complex-mediated (type 3), and cell-mediated (type 4) hypersensitivity reactions
. Presentation • Acute illness occurs upon exposure to substantial quantities of antigen, resulting in severe dyspnea, cough, and fever 4–6 hours post-exposure. Resolution transpires within 12 to 18 hours following the cessation of exposure. Chronic illness arises from extended exposure to little quantities of antigen, leading to a gradual onset of dyspnea, nonproductive cough, and exhaustion.
Radiology • High-resolution computed tomography (CT) reveals linear interstitial opacities and tiny nodules predominantly in the middle to upper lobes. • Frequently accompanied by traction bronchiectasis and honeycomb formations. Histopathology: Cellular chronic interstitial pneumonia with peribronchiolar accentuation. • Foci of organized pneumonia and ill-defined granulomas may also be observed.
Prognosis: Generally favorable if the culprit antigen is identified and exposure is prevented. Prolonged exposure may result in permanent pulmonary fibrosis and respiratory failure.
Definition: An interstitial lung disease resulting from an immunological response to inhaled antigens. Synonyms include extrinsic allergic alveolitis. Various versions of the disease are referred to by numerous alternative names, such as farmer’s lung, humidifier lung, maple bark stripper’s lung, mushroom worker’s lung, pigeon breeder’s lung, and bird fancier’s lung, among others.
Epidemiology: Rare occurrence.
Aetiology: • Thermophilic bacteria (found in moldy hay, compost, and air conditioning ducts), • Fungi (present in moldy maple bark, barley, or wood dust). • Avian proteins (excrement and plumage of birds).
Pathogenesis: Inhaled antigens provoke an aberrant immune response in the pulmonary system. • Comprises a synthesis of antibody-mediated (type 2), immune complex-mediated (type 3), and cell-mediated (type 4) hypersensitivity reactions
. Presentation • Acute illness occurs upon exposure to substantial quantities of antigen, resulting in severe dyspnea, cough, and fever 4–6 hours post-exposure. Resolution transpires within 12 to 18 hours following the cessation of exposure. Chronic illness arises from extended exposure to little quantities of antigen, leading to a gradual onset of dyspnea, nonproductive cough, and exhaustion.
Radiology • High-resolution computed tomography (CT) reveals linear interstitial opacities and tiny nodules predominantly in the middle to upper lobes. • Frequently accompanied by traction bronchiectasis and honeycomb formations. Histopathology: Cellular chronic interstitial pneumonia with peribronchiolar accentuation. • Foci of organized pneumonia and ill-defined granulomas may also be observed.
Prognosis: Generally favorable if the culprit antigen is identified and exposure is prevented. Prolonged exposure may result in permanent pulmonary fibrosis and respiratory failure.
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