Idiopathic Nonspecific Interstitial Pneumonia

NSIP is similar in clinical, radiologic, and pathologic presentation to chronic organizing pneumonia, IPF, and respiratory bronchiolitis associated interstitial lung disease (RB-ILD).

• Patients typically present with breathlessness and cough of usually 6 to 7 months duration³
• Inspiratory crackles are common¹
• Hypoxia may be seen in patients with more advanced disease¹
• Some patients may experience systemic signs or symptoms¹

• Weight Loss - 25%
• Fever - 22% 
• Arthralgias - 14%
• Raynaud phenomenon - 8% 
• Myalgias - 7%
• Skin rash - 5%
• Arthritis - 3% 

• FVC 
• DL_CO

Restrictive ventilatory patterns are observed on pulmonary function tests.³

• Features: Ground-glass opacities, reticular opacities with lower lung zone predominance, micronodules, consolidation, minimal honeycombing^3,5
  • A predominant finding of ground-glass abnormality is suggestive of cellular NSIP²
  • A predominant finding of reticulation in combination with ground glass opacity, traction bronchiectasis, and minimal honeycombing is indicative of fibrotic NSIP⁶
• Distribution: Predominantly diffuse or subpleural, symmetric distribution^3,5

• Used when HRCT suggests NSIP as NSIP pattern overlaps with organizing pneumonia and desquamative interstitial pneumonia⁷
• The key histopathologic feature of NSIP is the uniformity of interstitial involvement³
  • Pattern indicative of cellular NSIP shows mild to moderate interstitial chronic inflammation⁵
  • In cases of fibrosing NSIP, dense or loose interstitial fibrosis is observed⁵

• Microbiologic studies should be performed to exclude infections
• Cellular analysis should be performed to exclude malignancy 
• A differential cell count: >15% lymphocytes correlates with increased likelihood of NSIP⁸

When HRCT or biopsy is believed to show features of NSIP but there are incomplete data or the potential for an alternative diagnosis, the term NSIP pattern should be used. 

A multidisciplinary discussion involving pulmonologists, radiologists, and pathologists is advised in cases where the clinical, radiologic, and pathologic features are not definite or probable for NSIP.