Table 2 Distinguishing clinical features of idiopathic pulmonary fibrosis (IPF) and non-specific interstitial pneumonia (NSIP)
Clinical/radiographic/pathological featuresIPFNSIP
Duration of illnessChronic (>12 months)Subacute to chronic (months to years)
Frequency of diagnosis47–64%14–36%
Chest radiographBilateral reticular opacities in lower zones; volume loss; ± honeycombingBilateral hazy and reticular opacity
HRCTPeripheral, subpleural, basal predominancePeripheral, subpleural, basal, symmetrical
Reticular opacitiesGround-glass attenuation
Traction bronchiectasisLower lobe volume loss
Architectural distortion.
Focal ground-glass
Key histological featuresUsual interstitial pneumonia patternDense fibrosis causing remodeling of lung architecture with frequent “honeycomb” fibrosisFibroblastic foci typically scattered at the edges of dense scarsPatchy lung involvementFrequent subpleural and paraseptal distributionNSIP patternCellular patternMild to moderate interstitial chronic inflammationType II pneumocyte hyperplasia in areas of inflammationFibrosing patternDense or loose interstitial fibrosis lacking the temporal heterogeneity pattern and/or patchy features of UIPLung architecture may appear lost on examination of H&E stained sections but relatively preserved with elastic stainsInterstitial chronic inflammation (mild or moderate)
TreatmentPoor response to any treatmentCorticosteroid responsiveness
Prognosis50–70% mortality in 5 yearsUnclear; <15% mortality in 5 years
  • Adapted from American Thoracic Society/European Respiraratory Society.1