Allergic bronchopulmonary aspergillosis is an uncommon but serious respiratory condition characterized by chronic airway inflammation and airway damage resulting from persistent colonization by and sensitization to the fungus Aspergillus fumigatus.
Allergic bronchopulmonary aspergillosis (ABPA) is a severe complication in children, adolescents and adults with cystic fibrosis (CF), the prevalence of which ranges from 6-25%.
Physiopathology
The disease is the result of the colonisation of the respiratory tract by fungi of the genus Aspergillus, commonly Aspergillus fumigatus, and subsequent host sensitisation to fungal antigens, accompanied by a Th2 CD4 type response mediated by the production of specific IgE.
The immunopathogenesis of allergic bronchopulmonary aspergillosis involves several pathways.
Inhaled conidia of Aspergillus fumigatus are able to persist and germinate, releasing exoproteases and other fungal products that further compromise clearance, breach the epithelium, and activate immune responses. Chemotactic cytokines (e.g. IL-8, RANTES, eotaxin) in particular have been implicated in murine models.
Chemokine-mediated recruitment of CD4+TH2 lymphocytes specific for A. fumigatus is a crucial feature of ABPA. Susceptibility also appears to involve immunogenetic factors including atopy and defined major histocompatibility complex-restricted allelic expression on antigen-presenting cells that are permissive for a TH2-predominant immune response.
Aspergillus allergens stimulate an interleukin 5-mediated Th2 pathway responsible for the eosinophilic infiltrate, whereas aspergillus proteases promote epithelial activation and a potent chemokine response that induces neutrophilic airway inflammation.
The resulting airway inflammation is intense, involves tissue damage and remodeling, and is linked with the severity of bronchiectasis.
The consequent inflammatory and obstructive bronchopulmonary injury can progress to fibrosis.
Certain Aspergillus fumigatus allergens appear more associated with ABPA rather than simple Aspergillus fumigatus allergy.
ABPA is characterized by marked local and systemic eosinophilia, an adaptive immune response with elevated levels of A. fumigatus-specific IgG, IgA and IgE antibodies, and a profound nonspecific IL-4-dependent elevation in total IgE.
Synopsis
expectoration of mucus plugs
impaction of mucus plugs (mucoid impaction)
bronchial distension
proximal bronchiectasis (proximal bronchiectases)
sparse aspergillus hyphae in the mucus plugs
bronchial chronic inflammation
Association
Aspergillus allergy
- bronchocentric granulomatosis
- eosinophilic pneumonia
- extrinsic allergic alveolitis
Differential diagnosis
allergic bronchopulmonary fungal diseases
- allergic bronchopulmonary stemphyliosis
- allergic bronchopulmonary curvulariosis
- allergic bronchopulmonary drechsleriasis
- allergic bronchopulmonary candidosis
- allergic bronchopulmonary helminthosporiosis
- allergic bronchopulmonary penicilliosis
- allergic bronchopulmonary torulopsosis
- allergic bronchopulmonary fusariosis
- allergic bronchopulmonary pseudallescheriosis
See also
- saprophytic aspergillosis
-
pulmonary aspergillosis
- pulmonary aspergilloma
- pulmonary invasive aspergillosis
- allergic bronchopulmonary aspergillosis
- chronic bronchopulmonary aspergillosis (granulomatous bronchopulmonary aspergillosis)
- semi-invasive necrotic aspergillosis (16609531)
- Aspergillus-associated extrinsic allergic alveolitis
- Aspergillus clavatus
- patients harbouring an aspergilloma
Associations
cystic fibrosis (16473820)
References
Gibson PG. Allergic bronchopulmonary aspergillosis. Semin Respir Crit Care Med. 2006 Apr;27(2):185-91. PMID: 16612769
Moss RB. Pathophysiology and immunology of allergic bronchopulmonary aspergillosis. Med Mycol. 2005 May;43 Suppl 1:S203-6. PMID: 16110813