Non-specific interstitial pneumonia

Non-specific interstitial pneumonia, abbreviated NSIP, is an uncommon type of diffuse lung disease.

General

• Better prognosis than UIP.
• May respond to corticosteroids.
• Some radiologists and pathologists don't believe in this entity.^{[citation needed]}

Associations:

• Connective tissue disease.
• Rheumatoid arthritis.

Note:

• If no underlying cause is present it is known as idiopathic NSIP.

Gross/Radiology

• No honeycombing.
• Fibrosis usually lower lung zone.
• Patchy ground glass.

Microscopic

Features:

• Diffuse fibrosis:
  • Uniform fibrosis (unlike UIP).
  • "Linear fibrosis" has a good prognosis - should be mentioned in the report.
    • Linear fibrosis = fibrosis that follows alveolar walls + no architectural distortion.
• +/-Lymphoid nodules - association with collagen vascular disease. (???)
• +/-Focal organizing pneumonia.

Notes:

• Inflammation in NSIP usually more prominent than in UIP.
• No honeycombing - key difference between UIP and NSIP.

DDx:

• Collagen vascular disease.
• Drug reaction.
• Hypersensitivity pneumonitis (extrinic allergic alveolitis).
• Lymphocytic interstitial pneumonia (LIP) - much more inflammation.

See also

• Diffuse lung diseases.