Distinguishing features of the idiopathic interstitial pneumonias

	AIP	DIP	UIP
Prodrome	Abrupt (1 to 2 weeks)	Subacute (weeks to months)	Chronic (>12 months)
Chest radiography	Diffuse, bilateral air-space opacification	Ground-glass opacity in lower lung zones	Bilateral reticular opacities Honeycombing Lower zone predominance
HRCT features	Bilateral, symmetric areas of ground-glass opacity Bilateral air space consolidation	Diffuse ground-glass opacity in middle and lower lungzones	Intralobular interstitial opacities Irregular interlobular septal thickening Traction bronchiectasis and honeycombing Lower zone predominance
Histopathologic features	Diffuse, uniform organizing diffuse alveolar damage (hyaline membranes)	Diffuse, uniform intraalveolar macrophage accumulation	Variegated, patchy, subpleural interstitial fibrosisand honeycombing
Treatment	Mechanical ventilation Glucocorticoid responsiveness unknown	Glucocorticoid responsive	Poor response to glucocorticoids or cytotoxic agents
Prognosis	60 percent mortality in <6 months	5 percent mortality in 5 years	50 to 70 percent mortality in 5 years

AIP: acute interstitial pneumonia; UIP: usualinterstitial pneumonia; DIP: desquamative interstitial pneumonia; HRCT: high resolution CT scan.

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