Respiratory bronchiolitis, respiratory bronchiolitis-associated interstitial lung disease, and desquamative interstitial pneumonia: Different entities or part of the spectrum of the same disease process?

OBJECTIVE. Our objective was to assess high-resolution CT findings of respi ratory bronchiolitis, respiratory bronchiolitis-associated interstitial lun g disease, and desquamative interstitial pneumonia and to determine whether these three entities could be reliably differentiated by radiologic criter ia. MATERIALS AND METHODS. CT scans (1- to 3-mm collimation) were reviewed in 4 0 patients with pathologically proven respiratory bronchiolitis (n = 16), r espiratory bronchiolitis-associated interstitial lung disease (n = 8), or d esquamative interstitial pneumonia (n = 16). All patients with respiratory bronchiolitis and respiratory bronchiolitis-associated interstitial lung di sease were cigarette smokers, and 85% of the patients with desquamative int erstitial pneumonia had a history of smoking. CT scans were independently r eviewed by two radiologists who assessed the pattern and distribution of ab normalities. RESULTS, The predominant abnormalities in respiratory bronchiolitis were ce ntrilobular nodules (12 [75%] of 16 patients) and ground-glass attenuation (six [38%] of 16). No single abnormality predominated in the respiratory br onchiolitis-associated interstitial lung disease group; findings included g round-glass attenuation (four [50%] of eight), centrilobular nodules (three [38%] of eight), and mild fibrosis (two [25%] of eight). All patients with desquamative interstitial pneumonia showed ground-glass attenuation, and 1 0 (63%) of the 16 showed evidence of fibrosis. CONCLUSION. The significant overlap between the CT findings of respiratory bronchiolitis, respiratory bronchiolitis-associated interstitial lung disea se, and desquamative interstitial pneumonia is consistent with the concept that they represent different degrees of severity of small airway and paren chymal reaction to cigarette smoke.