Definition
Obliterative bronchiolitis (OB) is an irreversible lung disease that occurs in children and adults after injury to the lower respiratory tract. There is concentric narrowing and distortion of the bronchiole walls caused by inflammation and fibrosis. The alveoli are not involved. OB should not be confused with BOOP (Bronchiolitis Obliterans with Organising Pneumonia) from which it differs clinically, radiologically and histologically, and in response to steroids (Ryu 2003).
Causes
OB is a typical finding in bronchopulmonary dysplasia and cystic fibrosis.
Causes of OB include infection, transplantation, connective tissue disease,
toxic fume inhalation and aspiration. Many cases are idiopathic. The
most common cause of OB in children is following acute viral lower respiratory
tract infection, with adenovirus being the agent most commonly implicated.
Other agents associated with post-infectious OB include mycoplasma, measles,
influenza and respiratory syncytial virus (Chan 2004).
Clinical Presentations
OB can be mistaken for asthma as some of the presenting symptoms such
as cough, wheezing and dyspnoea are similar. OB should be suspected
if symptoms persist, exercise intolerance is prolonged and respiratory
symptoms are disproportionately severe to chest X-ray findings.
Investigations
Lung biopsy does not always confirm the diagnosis of OB because of the
patchy distribution of disease and diagnosis is usually based on a
combination of history, physical examination, chest X-ray, pulmonary
function tests and HRCT. HRCT features may include "mosaic" shadowing
emphasised in expiration, bronchial wall thickening, hyperlucent lung
and bronchiectasis (Lynch 1999).
Treatment
Treatment of OB is mainly supportive, and includes antibiotics and physiotherapy
plus oxygen therapy, if the patient is hypoxic. Many patients are treated
empirically with bronchodilators and corticosteroids and responses
may be variable. There have been no published randomised controlled
trials of any treatment. Surgery may be an option for a small number
of patients with severe localised disease and lung transplantation
is an option in end-stage disease. The clinical course is very variable
and the prognosis for any individual is often difficult to predict.
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Useful references:
Bronchiolar Disorders: state of the Art
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Ryu JH, Myers JL, Swensen SJ.
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Am J Respir Crit Care Med 2003. 168:1277-92
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Bronchiolitis Obliterans: an update
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Chan A and Roblee A.
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Curr Opin Pulm Med 2004. 10:133-141
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Pediatric Diffuse Lung
Disease: Diagnosis and Classification using High-resolution
CT
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Lynch DA, Hay T, Newell JD, Divgi VD, Fan LL.
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Am J Roentgen 1999. 173:713-718
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Web links:
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