Respiratory Bronchiolitis Associated Interstitial Lung Disease
Definition
- Bronchiolocentric accumulations of macrophages with symptomatic interstitial lung disease
Diagnostic Criteria
- Clinical
- Essentially all affected patients are smokers
- Adults most are 30-60
- Identical histologic changes may be seen in asymptomatic smokers; the diagnosis requires clinically significant disease
- Chronic dyspnea, cough
- Pulmonary function tests
- Usually mild restrictive or mixed restrictive/obstructive
- Decreased diffusing capacity in the absence of airflow obstruction
- Good response to smoking cessation
- High resolution computed tomography (HRCT)
- Centrilobular nodules
- Ground glass opacities
- Histopathologic features
- Patchy bronchiolocentric process
- Intervening lung tissue is not affected
- Intralumenal macrophage accumulation centered on respiratory bronchioles
- Macrophages fill bronchiole and adjacent alveoli
- Macrophages contain finely granular golden brown pigment
- Iron positive
- Termed "smokers macrophages"
- Mild to moderate fibrosis may surround the bronchiole and involve adjacent alveolar septa
- Pulmonary architecture is preserved
- Mild interstitial infiltrate of histiocytes and plasma cells may be present in the same regions
- Reactive alveolar lining cells may be present
- Occurring in smokers' lungs, other clinicopathologic disorders such as chronic bronchitis and emphysema are frequently present
- Patchy bronchiolocentric process
- All other types of interstitial lung disease must be ruled out
- Features of other types of interstitial lung disease should not be present
- Diffuse filling of alveoli by macrophages typical of DIP, see note below
- Focal fibroblastic foci or honeycomb pattern typical of UIP
- Diffuse involvement of NSIP
- Hyaline membranes or organization of AIP
- Bronchiolitis obliterans / organizing pneumonia
- The following features should not be seen
- Granulomas or giant cells
- Foreign material other than anthracotic pigment
- More than rare eosinophils
- Evidence of infection
- Features of other types of interstitial lung disease should not be present
- May form a spectrum with desquamative interstitial pneumonia
- Patchy (RBAILD) vs. diffuse (DIP) airspace involvement by macrophages
Gerald J Berry MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
