Allergic bronchopulmonary aspergillosis
4922861
224861760
2008-07-10T19:11:42Z
Arcadian
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infobox/nav
{{Infobox_Disease |
Name = Allergic bronchopulmonary aspergillosis|
DiseasesDB = |
ICD10 = |
ICD9 = {{ICD9|518.6}} |
ICDO = |
OMIM = 103920 |
MedlinePlus = 000070 |
eMedicineSubj = |
eMedicineTopic = |
eMedicine_mult = {{eMedicine2|radio|55}} |
MeshID = D001229 |
}}
In [[medicine]], '''allergic bronchopulmonary aspergillosis''' ('''ABPA''') is a condition characterised by an exagerated response of the [[immune system]] (a [[Hypersensitivity|hypersensitivity response]]) to the [[fungus]] ''[[Aspergillus]]'' (most commonly ''[[Aspergillus fumigatus]]''). It occurs most often in patients with [[asthma]] or [[cystic fibrosis]]. ''Aspergillus'' [[spore]]s are ubiquitous in soil and are commonly found in the [[sputum]] of healthy individuals. ''A. fumigatus'' is responsible for a spectrum of lung diseases known as [[aspergillosis|aspergilloses]].
ABPA causes [[airway]] [[inflammation]] which can ultimately be complicated by sacs of the airways ([[bronchiectasis]]). The disease may cause airway constriction ([[bronchospasm]]). Besides asthma and cystic fibrosis, ABPA can also resemble other conditions such as [[eosinophilic pneumonia]].
The exact criteria for the diagnosis of ABPA are not agreed upon. [[Chest X-ray]]s and [[CT scan]]s, raised blood levels of [[Immunoglobulin E|IgE]] and [[eosinophilia|eosinophil]]s, immunological tests for ''Aspergillus'' together with sputum [[Gram staining|staining]] and [[sputum culture]]s can be useful. [[Biopsy|Biopsies]] are rarely needed. Treatment consists of [[corticosteroids]] and [[antifungal]] medications.
==Symptoms==
Patients with allergic bronchopulmonary aspergillosis often have [[symptom]]s of poorly controlled [[asthma]], with [[wheezing]], [[cough]], [[shortness of breath]] and [[exercise intolerance]]. They also have symptoms reminding of [[bronchiectasis]], such as chronic [[sputum]] production, coughing up brownish mucoid plugs or even blood (the latter is called [[hemoptysis]]), and recurrent infections (with [[fever]] and [[malaise]]). However, since the infiltrates in ABPA indicate [[eosinophilic pneumonia]], they do not respond to treatment with [[antibiotics]]. There may be unexplained worsening of asthma or [[cystic fibrosis]].
==Diagnosis==
A full blood count usually reveals [[eosinophilia]] more than 10% and there is a raised serum IgE more than 1000ng/ml.
''Chest radiography'' shows various transient abnormalities:
*consolidation, infiltrates or collapse
*thickened bronchial wall markings
*peripheral shadows
*signs of [[bronchiectasis]], typically in a central location
''Aspergillus specific tests'':
*precipitating antibodies to aspergillus species in >90% of cases
*aspergillus-specific IgE [[RAST test]]
*skin-prick test is almost always positive to Aspergillus fumigatus
Fungal hyphae may be seen in the sputum.
==Treatment==
The aim of treatment is to suppress the immune reaction to the fungus and to control bronchospasm.
The immune reaction is suppressed using oral [[corticosteroids]]:
*a high dose of [[prednisolone]] or [[prednisone]] (30 to 45 mg per day) in acute attacks
*a lower maintenance dose (5-10 mg per day)
Mucus plugs may be removed by bronchoscopic aspiration. It is almost impossible to eradicate the fungus but sometimes [[itraconazole]] (an anti-fungal) is used in combination with steroid therapy. Regular monitoring of the condition includes chest x-rays, [[spirometry|pulmonary function tests]], and serum IgE. The antibody levels usually fall as the disease is controlled, but they may rise again as an early sign of flare-ups.
==Epidemiology==
Estimating the prevalence of ABPA has been made difficult by lack of uniform diagnostic criteria and standardised tests. It usually occurs as a complication of other chronic lung disease, in particular [[asthma]] or [[cystic fibrosis]]. It is estimated that ABPA may be present in between 0.5 and 2% of all asthma patients, and in between 1 and 15% of cystic fibrosis patients.<ref name="pmid12975753">{{cite journal |author=Stevens DA, Moss RB, Kurup VP, ''et al'' |title=Allergic bronchopulmonary aspergillosis in cystic fibrosis--state of the art: Cystic Fibrosis Foundation Consensus Conference |journal=Clin. Infect. Dis. |volume=37 Suppl 3 |issue= |pages=S225–64 |year=2003 |month=October |pmid=12975753 |doi= |url=http://www.journals.uchicago.edu/cgi-bin/resolve?CID31034}}</ref>
==Disease mechanism==
For an unknown reason, patients with allergic bronchopulmonary aspergillosis develop a [[hypersensitivity response]], both a [[type I hypersensitivity|type I]] response ([[atopy|atopic]], with formation of [[immunoglobulin E]] or IgE) and a [[type III hypersensitivity]] response (with formation of [[immunoglobulin G]] or IgG). The reaction of immunoglobulin E with Aspergillus [[antigen]]s results in [[mast cell]] [[degranulation]] with [[bronchoconstriction]] and increased [[capillary]] [[Vascular permeability|permeability]]. Immune complexes (a type III reaction) and inflammatory cells are then deposited within the [[mucous membrane]]s of the airways, leading to [[necrosis]] (tissue death) and an [[Eosinophil granulocyte|eosinophilic]] infiltrate. Type 2 [[T helper cell]]s secreting [[interleukin 4]] and [[interleukin 5]], and attraction of [[neutrophil granulocyte|neutrophils]] by [[interleukin 8]] seem to play an important role.
In spite of this pronounced immune reaction, the fungus is not cleared from the airways. The subsequent damage to the bronchial wall caused by [[proteolytic enzyme]]s released by the immune cells and toxins released by the fungi results in [[bronchiectasis]], most pronounced in the central parts of the airways. Repeated acute episodes left untreated can result in progressive pulmonary [[fibrosis]] that is often seen in the upper zones and can give rise to a similar radiological appearance to that produced by [[tuberculosis]].
This model explains the main features of episodic bronchospasm, increased mucus production and plugging of distal airways, leading to their collapse and subsequent bronchiectasis.
==References==
*{{cite book | last = Kumar | first = Parveen | title = Clinical Medicine | publisher = W.B. Saunders | location = Philadelphia | year = 1998 | isbn = 0702020192 }}
*{{cite book | last = Longmore | first = Murray | title = Oxford Handbook of Clinical Medicine | publisher = Oxford University Press | location = Oxford Oxfordshire | year = 2004 | isbn = 0198525583 }}
*{{cite journal |author=Greenberger PA, Patterson R |title=Allergic bronchopulmonary aspergillosis and the evaluation of the patient with asthma |journal=J. Allergy Clin. Immunol. |volume=81 |issue=4 |pages=646-50 |year=1988 |pmid=3356845}}
*V.P.Kurup, B.Banerjee, P.A.Greenberger, J.N.Fink. ''Allergic Bronchopulmonary Aspergillosis: Challenges in Diagnosis''. From Medscape General Medicine. [http://www.medscape.com/viewarticle/408747_1/ full text]
==Footnotes==
<references/>
==External links==
*[http://www.gpnotebook.co.uk/simplepage.cfm?ID=1100611584 Allergic Bronchopulmonary Aspergillosis] - GP Notebook
*[http://www.merck.com/mmhe/sec04/ch051/ch051d.html Allergic Bronchopulmonary Aspergillosis] - The Merck Manuals Online Medical Library
*[http://rad.usuhs.mil/medpix/medpix.html?mode=caption_search&srchstr=allergic+bronchopulmonary+aspergillosis#top/ Medpix. ABPA radiology pictures]
{{Allergic conditions}}
{{Respiratory pathology}}
[[Category:Aspergillus]]
[[Category:Fungal diseases]]
[[de:Allergische bronchopulmonale Aspergillose]]
[[fr:Aspergillose bronchopulmonaire]]