Diffuse Parenchymal Lung Disease (12/7/16) - Scardella

Question 1

Restrictive Diseases

Spirometry findings

Most common cause

Answer 1

Inability to fill the lungs

Spirometry findings:

• Dec. TLC, dec. FEV₁, and dec. FVC
• FEV₁:FVC ratio inc.
  
  • 4/5 = 80% (normal) vs 3.5/4 = > 85% (restrictive)
  • Inc. elastic recoil of lung allows you to expire air more quickly over that 1st sec

Most common cause:

• Interstitial diseases of the lung
  
  • Thickened wall → impaired gas exchange
• May also arise with chest wall abnormalities (e.g., massive obesity)

Question 2

Types of restrictive diseases (4)

Answer 2

• Idiopathic pulmonary fibrosis
• Pneumoconioses
• Sarcoidosis
• Hypersensitivity pneumonitis

Question 3

Idiopathic pulmonary fibrosis

Answer 3

• Fibrosis of lung interstitium
• Etiology unknown → likely related to cyclical lung injury then cyclical healing
  
  • ​TGF-beta from injured pneumocytes induces fibrosis
• Secondary causes of IF must be excluded:
  
  • Drugs (e.g., bleomycin, amiodarone)
  • Radiation therapy

Question 4

Pneumoconioses

Entity (4)

Answer 4

• Interstital fibrosis due to occupational exposure
• Requires chronic exposure to small fibrogenic particles
  
  • Alveolar macrophages (at bottom of lung) engulf foreign particles and induce fibrosis

Entity

• Coal workers’ pneumoconiosis
• Silicosis
• Berylliosis
• Asbestosis

Question 5

Sarcoidosis

Answer 5

• Systemic disease characterized by noncaseating granulomas in multiple organs - classically seen in AA females
• Etiology = unknown
  
  • Likely due to CD4+ helper T-cell response to unknown antigen
• Granulomas most commonly involve hilar lymph nodes and lung → restrictive lung disease
  
  • Histo: stellate inclusions (‘asteroid bodies’) seen within giant cells of granulomas
• Almost any tissue can be involved
• Clinical features:
  
  • Dyspnea or cough (most common presenting symptom)
  • Elevated serum ACE
  • Hypercalcemia (1-alpha hydroxylase activity of epithelioid histiocytes converts vitamin D to active form)
  • Treatment = steroids
    
    • Often resolves spontaneously without treatment

Question 6

Hypersensitivity Pneumonitis

Answer 6

• Granulomatous (eosinophilic) rxn to inhaled organic antigens (e.g. pigeon breeder’s lung)
• Presents w fever, cough, dyspnea hours after exposure
  
  • Resolves without removal of exposure
  • If constantly exposed → restrictive lung disease