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 respiratory bronchiolitis, respiratory bronchiolitis-associated interstitial lung disease, and desquamative interstitial pneumonia and to determine whether these three entities could be reliably differentiated by radiologic criteria.
MATERIALS AND METHODS: CT scans (1- to 3-mm collimation) were reviewed in 40 patients with pathologically proven respiratory bronchiolitis (n = 16), respiratory bronchiolitis-associated interstitial lung disease (n = 8), or desquamative interstitial pneumonia (n = 16). All patients with respiratory bronchiolitis and respiratory bronchiolitis-associated interstitial lung disease were cigarette smokers, and 85% of the patients with desquamative interstitial pneumonia had a history of smoking. CT scans were independently reviewed by two radiologists who assessed the pattern and distribution of abnormalities.
RESULTS: The predominant abnormalities in respiratory bronchiolitis were centrilobular nodules (12 [75%] of 16 patients) and ground-glass attenuation (six [38%] of 16). No single abnormality predominated in the respiratory bronchiolitis-associated interstitial lung disease group; findings included ground-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 10 (63%) of the 16 showed evidence of fibrosis.
CONCLUSION: The significant overlap between the CT findings of respiratory bronchiolitis, respiratory bronchiolitis-associated interstitial lung disease, and desquamative interstitial pneumonia is consistent with the concept that they represent different degrees of severity of small airway and parenchymal reaction to cigarette smoke.