Respiratory Bronchiolitis/Interstitial Lung Disease: Fibrosis, Pulmonary Function, and Evolving Concepts by ProQuest


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									         Respiratory Bronchiolitis/Interstitial Lung Disease
                        Fibrosis, Pulmonary Function, and Evolving Concepts
                              Andrew Churg, MD; Nestor L. Muller, MD, PhD; Joanne L. Wright, MD

● Context.—The concept of respiratory bronchiolitis/inter-            associated with airflow obstruction. Further, interstitial
stitial lung disease (RBILD) was introduced to explain the            fibrosis is sometimes found in centrilobular emphysema,
presence of interstitial lung disease in individuals whose            and this phenomenon has probably lead to some cases of
only finding on surgical lung biopsy was smoker’s respira-             centrilobular emphysema being misclassified as RB or
tory bronchiolitis (RB). Over time, the diagnostic criteria           RBILD. Despite the presence of fibrosis, centrilobular em-
for RBILD have become progressively more confused.                    physema is still associated with airflow obstruction. We
   Objective.—To review the diagnostic criteria for RBILD.            suggest that RBILD be restricted to the clinical setting in
   Design.—The review was based on the literature and                 which cigarette smokers have a restrictive or mixed ob-
personal experience.                                                  structive and restrictive functional abnormality, have a
   Conclusions.—The concept of RBILD has changed over
                                                                      marked decrease in diffusing capacity with minimal evi-
time with the recognition that, histologically and radio-
logically, RB and RBILD are usually indistinguishable.                dence of airflow obstruction, or have imaging studies
Most authors accept mild alveolar wall fibrosis extending              showing ground glass opacities/centrilobular nodules plus
away from the respiratory bronchioles as a part of both               reticulation and no other lesion besides RB on biopsy to
RB and RBILD, and occasional cases show quite marked,                 account for these changes. In this setting, the presence of
but probably localized, interstitial fibrosis. What has not            RB-associated interstitial fibrosis probably causes the
been appreciated is that RB is not only an extremely com-             functional changes.
mon disease in cigarette smokers but also is ordinarily                  (Arch Pathol Lab Med. 2010;134:27–32)

T   he concept of respiratory bronchiolitis/interstitial lung
     disease (RBILD) was introduced in 1987 by Myers et
al1 as a morphologic explanation for clinical interstitial
                                                                      are associated with heavy smoking (mean pack-years
                                                                      ranging from 29 to 54 in published series1,4–7), and this, of
                                                                      course, makes such patients candidates for chronic ob-
lung disease (explicitly, in their article, restrictive pulmo-        structive pulmonary disease (COPD), a process that po-
nary function tests and/or interstitial markings on plain             tentially confounds the diagnosis of RBILD pathologically,
chest radiographs) in 6 patients in whom nothing besides              radiologically, and on pulmonary function testing. Mor-
smoker’s respiratory bronchiolitis (RB) could be found on             phologic lesions of COPD, where reported, are indeed
surgical lung biopsy. Since that time, there have been few            common; for example, 9 of 10 patients with RBILD (90%),
cases reported, and arguments continue back and forth                 described by Moon et al,4 had centrilobular emphysema
about what histologic features, what radiologic features,             (see comments below on imaging).
and what clinical features define this condition,2 and the                We were asked to specifically address the issue of fibro-
diagnostic criteria have become progressively murkier. In-            sis and its significance in RBILD in this brief review, but
deed, Wells et al3 have concluded that the diagnosis of               in doing so, it has become apparent that there are 2 pools
RBILD ‘‘remains a nebulous gestalt of clinical, functional,           of knowledge: 1 related to interstitial lung diseases and
and HRCT [high-resolution computed tomography] find-                   their pathologic correlates, and the other related to COPD
ings. . . . ’’                                                        and its pathologic correlates. Here, we attempt to put these
   Respiratory bronchiolitis/interstitial lung disease and            2 schools together and to suggest what this means for di-
smoker’s RB are diseases of cigarette smokers (with 1 ex-             agnosing RBILD.
ceptional case, to our knowledge, occurring in a non-
smoker exposed to solder flux).4 Cases reported as RBILD                        MORPHOLOGIC FINDINGS IN RBILD
                                                                        In the original article of Myers et al,1 the major patho-
  Accepted for publication September 22, 2008.                        logic finding was the presence of RB: clusters of slightly
  From the Department of Pathology, University of British Columbia,   golden colored alveolar macrophages (‘‘smoker’s macro-
Vancouver, Canada (Drs Churg and Wright); and the Department of       phages’’) in the lumens of respiratory bronchioles, alveolar
Radiology, Vancouv
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