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Interstitial Lung Disease

Interstitial Lung Disease. Pulmonary interstitium. Alveolar lining cells (types 1 and 2) Thin elastin-rich connective component containing capillary blood vessels. Interstitial lung disease. Increase in interstitial tissue causing “stiffness” Physiological restrictive defect

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Interstitial Lung Disease

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  1. Interstitial Lung Disease

  2. Pulmonary interstitium • Alveolar lining cells (types 1 and 2) • Thin elastin-rich connective component containing capillary blood vessels

  3. Interstitial lung disease • Increase in interstitial tissue causing “stiffness” • Physiological restrictive defect • Alveolar-capillary interface is site of injury • Acute and chronic disease • Lots of causes/patterns!

  4. Interstitial lung disease • Early stage and acute is alveolitis (injury with inflammatory cell infiltration) • Late stage characterised by fibrosis Clinical effects due to hypoxia (respiratory failure) and cardiac failure

  5. Causes…. • Environmental (mineral dusts, drugs, radiation. Post-ARDS) • Hypersensitivity (mouldy hay, avian proteins) • Unknown (idiopathic) • Connective tissue diseases • Idiopathic pulmonary fibrosis Diagnosis based on clinical features often with biopsy

  6. Biopsy in interstitial lung disease… • Transbronchial biopsy – special forceps used at bronchoscopy • Thoracoscopic biopsy – more invasive but more reliable and generates far more tissue

  7. ARDS (adult respiratory distress syndrome) • Classic model of acute interstitial injury • Diffuse alveolar damage syndrome (DADS) • Shock lung • Causes include sepsis, diffuse infection (virus, mycoplasma), severe trauma, oxygen

  8. Pathogenesis of ARDS Injury (eg bacterial endotoxin) • Injury to cell membranes (either alveolar epithelial cells or endothelial cells) • Infiltration of inflammatory cells • Cytokines • Oxygen free radicals

  9. Pathology of ARDS • Fibrinous exudate lining alveolar walls (hyaline membranes) • Cellular regeneration • Inflammation

  10. ARDS with hyaline membrane

  11. ARDS – cellular reaction

  12. Outcome of ARDS • Death • Resolution • Fibrosis (chronic restrictive lung disease)

  13. Neonatal RDS • Premature infants • Deficient in surfactant (type 2 alveolar lining cells • Increased effort in expanding lung physical damage to cells

  14. Chronic Interstitial Disease • Idiopathic pulmonary fibrosis (IPF) • Sarcoidosis • Extrinsic allergic alveolitis (hypersensitivity pneumonitis) • Pneumoconiosis • Connective tissue diseases

  15. IPF • aka cryptogenic fibrosing alveolitis (CFA), usual interstitial pneumonia (UIP) • Progressive interstitial fibrosis of unknown cause • Variable associated inflammation • Finger clubbing

  16. Pathology • Subpleural and basal fibrosis • Inflammatory component variable • Terminally lung structure replaced by dilated spaces surrounded by fibrous walls

  17. Fibrosing alveolitis (early)

  18. IPF (late – honeycombing)

  19. Honeycomb lung • Subpleural “enlarged” spaces with fibrous walls • A powerful “splint” effect – like a plaster cast

  20. Honeycombing – basal/subpleural (a splint!)

  21. Chronic inflammatory disease Small airways Interstitium Occasional granulomas Allergic origin Type III hypersensitivity Type IV hypersensitivity Extrinsic allergic alveolitis (hypersensitivity pneumonitis)

  22. Inflammation in hypersensitivity pneumonitis

  23. Causes of EAA • Thermophilic bacteria – Farmers lung • Avian proteins – Bird fanciers lung • Fungi – Malt workers lung Precipitins (antibodies) often detectable in serum. Unusual cases come to biopsy.

  24. Sarcoidosis • Multisystem granulomatous disorder of unknown cause (defined by histological means) • Pulmonary involvement is common • Most cases mild and self-limiting • In US 10 times commoner in black vs. white

  25. Other manifestations of sarcoidosis • Uveitis (inflammation of iris) • Erythema nodosum • Lymphadenopathy • Hypercalcaemia

  26. Transbronchial biopsy - sarcoidosis

  27. Sarcoidosis - granuloma

  28. Pulmonary involvement in connective tissue diseases • Interstitial fibrosis (milder than fibrosing alveolitis) • Pleural effusions • Rheumatoid nodules

  29. Pneumoconiosis Lung disease caused by mineral dust exposure • Asbestosis • Coal workers lung • Silicosis

  30. Thin whole mount section of a coal-workers lung (unstained)

  31. Coal miner with progressive massive fibrosis (unstained)

  32. Disease depends on…. • Particle size (1-5mm) • Reactivity of particle • Clearance of particle • Host response

  33. Asbestos • A silicate • Serpentine (curved) asbestos fibres relatively safe • Straight (amphibole) asbestos highly dangerous

  34. Asbestosis bodies (from human lung)

  35. Association of asbestos bodies with fibrosis (asbestosis)

  36. Pleural plaque on diaphragm

  37. Pulmonary eosinophilia Alveolar infiltration by eosinophils: • Tropical eosinophilia – associated with migration of microfilariae through the lung • Other eosinophilic “pneumonias” – a range of immune responses • Often acutely sensitive to treatment with steroids

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