A 77-year-old woman with a history of left lower lobectomy for a lung carcinoid tumor presented with dyspnea and cough. A chest radiograph (figure 1) showed diffuse bilateral patchy nodular infiltrates. A thin-section chest CT (figure 2) was performed 4 days later.
Prepared by Lewis H. MacLaughlin, MD and Mark A. King, MD
of the Department of Radiology, The Ohio State University
Medical Center, Columbus, OH.
A 77-year-old woman with a history of left lower lobectomy for a
lung carcinoid tumor presented with dyspnea and cough. A chest
radiograph (figure 1) showed diffuse bilateral patchy nodular
infiltrates. A thin-section chest CT (figure 2) was performed 4
Bronchiolitis obliterans organizing pneumonia (BOOP)
Bronchiolitis obliterans can be categorized histologically into
two morphological types: constrictive bronchiolitis and
proliferative bronchiolitis obliterans.
Constrictive bronchiolitis involves concentrically scarred or
obliterated bronchioles with less involvement of the distal
alveolar ducts and alveoli.
Proliferative bronchiolitis obliterans involves organizing
granulation tissue polyps filling the lumen of terminal and
respiratory bronchioles. It usually extends contiguously into
alveolar ducts, and sometimes into distal alveoli resulting in
While primary or idiopathic BOOP is the most common cause of
proliferative bron-chiolitis obliterans, it may also be secondary
to rheumatologic or connective tissue disorders, adult respiratory
distress syndrome (ARDS), infection, aspiration pneumonia,
hypersensitivity pneumonitis, toxic fume exposure, eosinophilic
pneumonia, post-obstructive pneumonia, post-bone marrow or lung
transplantation, or other miscellaneous conditions (HIV infection,
radiation therapy, cancer, inflam-matory bowel disease, textile
BOOP is defined pathologically as granulation tissue plugs
within the lumens of small airways that may result in their
complete obstruction, with granulation tissue extending into
alveolar ducts and alveoli
(figure 3). Additional findings include connective tissue
proliferation resulting in intraluminal polyps (proliferative
bronchiolitis obliterans), fibrinous exudates, alveolar walls, and
evenly spaced rounded balls of myxomatous connective tissue.
The lung architecture is maintained.
In this case, a video-assisted thorascopic wedge biopsy of the
right lower lobe revealed polymorphonuclear leukocytes in the
airways obliterating the bronchioles in a background of an
organizing pneumonia, with inflammation and fibrosis.
Clinically, patients with BOOP most often present with a 2- to
12-week history of cough, dyspnea, and malaise (each present in
over 80% of patients).
Fever and weight loss are common. Crackles (over 80% of patients)
and tachypnea (over 60% patients)
are the most frequent findings on examination. Men and women are
affected at equal rates,
and no relationship to smoking exists.
Pulmonary function studies show decreased vital capacity, normal
flow rates (except in smokers), and decreased diffusing capacity.
Common laboratory abnormalities include hypoalbuminemia,
leukocytosis, and an increased erythrocyte sedimentation rate.
Bronchoalveolar lavage reveals an increase in all cell types, with
Definitive diagnosis is established pathologically following open
lung biopsy or video-guided thoracoscopy.
Radiographically, bilateral patchy alveolar infiltrates that may
be migratory are the most common finding.
Cavities and effusions are rare.
In idiopathic BOOP, the infiltrates typically enlarge gradually, or
new infiltrates appear as the disease progresses.
On CT, BOOP typically presents as bilateral non-segmental
consolidations (present in 79% of patients),
or areas of ground-glass opacity that are usually subpleural or
peribronchovascular in location. Peripheral patchy infiltrates may
form a characteristic triangular shape, with the base of the
triangle directed toward the pleura.
A frequent CT finding is nodules (found in 30% of patients) with
well-defined, smooth margins, that are distributed randomly.
A pulmonary vessel leading into the nodule (the "feeding vessel
sign") or an air bronchogram entering the nodule (the "bronchus
sign") may be observed.
In this case, numerous small, ill-defined nodules with irregular
margins were found in association with irregular peripheral masses
and evidence of airway disease on CT. Although the patient in this
case had a history of a primary pulmonary tumor, the CT findings
made metastatic disease unlikely.
Most BOOP patients respond to corticosteroid therapy, and
prednisone remains the recommended therapy.
The prognosis for BOOP is good. Total and permanent recovery is
seen in 65% to 80% of patients treated.
The mortality remains approximately 5%.
Acknowledgement: The authors would like to thank Mark D.
Brownell, MD, for his kind assistance with interpretation and
photography of the lung biopsy specimen.