Uncategorized

• What is it?
  • Pneumonitis refers to inflammation of the lung parenchyma, typically caused by non-infectious processes, although viral infections can also lead to pneumonitis in certain contexts.
• Classified as:
  • A broad term encompassing a range of inflammatory lung conditions.
• Caused by:
  • Exposure-related:
    • Hypersensitivity pneumonitis (e.g., bird fancier?s lung, farmer?s lung).
    • Radiation pneumonitis (e.g., following thoracic radiotherapy).
    • Drug-induced pneumonitis (e.g., caused by amiodarone, methotrexate).
  • Systemic diseases:
    • Autoimmune conditions (e.g., rheumatoid arthritis, systemic lupus erythematosus).
    • Vasculitis (e.g., granulomatosis with polyangiitis).
  • Idiopathic forms:
    • Cryptogenic organizing pneumonia (COP).
    • Acute interstitial pneumonitis (AIP).
• Resulting in:
  • Impaired gas exchange due to alveolar inflammation and/or interstitial fibrosis.
  • Potential progression to permanent scarring in chronic cases.
• Characterized by:
  • Variable clinical presentation ranging from asymptomatic to progressive dyspnea and cough.
  • Imaging findings that often include ground-glass opacities, reticulations, or consolidation.
• Anatomically affecting:
  • Alveoli, interstitium, and in some cases, the airways or pleura.
• Pathophysiology:
  • Initial insult triggers an inflammatory response involving the alveoli and interstitium.
  • Chronic inflammation may lead to fibroblast activation and extracellular matrix deposition, resulting in fibrosis.
• Diagnosis:
  • Clinical:
    • Symptoms include dyspnea, non-productive cough, and fatigue.
    • History of exposure or underlying systemic disease is often relevant.
  • Imaging:
    • Radiologic Principles:
      • Detection of inflammation or fibrosis in the lung parenchyma.
    • Applied Anatomy:
      • Parts: Alveoli, interstitial spaces, airways.
      • Size: Diffuse or localized involvement.
      • Shape: Reticular, nodular or reticulonodular pattern, ground-glass opacities.
      • Position: Diffuse or basal predominance depending on etiology.
      • Character: a pattern of ground-glass opacities with ill-defined, centrilobular nodules, often seen as a nodular or reticulonodular pattern
      • Time: Acute or chronic depending on the cause.
    • CXR:
      • Diffuse or localized opacities; often non-specific.
    • CT:
      • Pattern of ground-glass opacities with ill-defined, centrilobular nodules, often seen as a nodular or reticulonodular pattern.
      • Perilobular distribution in organizing pneumonia.
    • PET-CT:
      • Increased metabolic activity in areas of inflammation.
  • Laboratory findings:
    • PFTs: Restrictive or mixed restrictive-obstructive patterns.
    • Bloods: Elevated inflammatory markers (e.g., ESR, CRP); hypersensitivity panels if indicated.
    • Pathology: Biopsy may show alveolar inflammation, interstitial infiltrates, or organizing fibrosis.
• Treatment:
  • Remove or minimize exposure to causative agents.
  • Corticosteroids are often first-line therapy.
  • Immunosuppressants (e.g., azathioprine, mycophenolate) for autoimmune-related pneumonitis.
• Prognosis:
  • Depends on the underlying cause and timely management.
  • Chronic exposure or delayed treatment may lead to irreversible fibrosis.
• Radiological Implications:
  • Imaging is critical for early detection and monitoring of treatment response.
  • Distinguishing pneumonitis from infectious pneumonia is key based on clinical and imaging findings.
• Key Points and Pearls:
  • Pneumonitis is primarily non-infectious and requires clinical correlation for diagnosis.
  • Imaging findings are non-specific and overlap with many interstitial lung diseases.
  • Hypersensitivity pneumonitis often presents with centrilobular nodules or ground-glass opacity in upper lobes.
  • Early recognition and management of causative factors are crucial to prevent progression to fibrosis.