Asthma (Etiology, Epidemiology, Pathology and Risk Factors) Flashcards
(47 cards)
What is asthma?
Asthma, whatever the severity, is a chronic inflammatory disorder of the airways mediated by mast cells, eosinophils and T-lymphocytes
- inflammation underpins the whole entity
What does airway inflammation contribute to?
- airway hyper-responsiveness (bronchoconstriction)
- airflow limitation
- respiratory symptoms (cough, wheezing etc.)
- disease chronicity (if inflammation not addressed)
What does the inflammation cause?
Recurrent wheezing, breathlessness, chest tightness and cough, particularly at night, and is associated with widespread but variable obstruction that is at least partly reversible.
- the inflammation causes airway hyper-responsiveness
- fixed airway obstruction may occur (NB! due to scar formation occurring in the airways)
What are the 3 key words in asthma?
- Inflammation
- Airway hyper-responsiveness
- Airway remodeling
What is another term for airway hyper-responsiveness?
Airway hyper-reactivity
What is airway remodeling?
Describes what happens as a consequence of chronic asthma
- hypertrophy and hyperplasia of smooth muscle and subepithelial fibers
What is asthma often described as?
A chronic eosinophilic bronchitis
Pathology of asthma:
Changes include muscosal oedema, mucus hypersecretion, smooth muscle hypertrophy, loss of airway epithelium and infiltration of inflammatory cells
Asthma aetiology
Asthma occurs in a given individual as a result of a combination of genetic predisposition and exposure to appropriate environmental stimuli
What are “inducers”?
e.g. allergens or occupational agents
- cause airway inflammation, bronchial hyper-reactivity and symptoms of asthma
= disease is brought on
What are “trigger factors”?
e.g. exercise or irritants result in exacerbations of asthma
= disease is already there, something makes it worse
Which antibodies are involved in asthma?
IgE
Who is likely to get asthma?
A number of factors determine the likelihood of developing asthma
- following exposure to an irritant in the air a normal immune and defense response occurs; in people with asthma the response may become exaggerated
- airway inflammation and hyper-reactivity
i. e. airways would over-react to things that would just be minor irritants in people without asthma
What are the two types of asthma conventionally described?
- Extrinsic (atopic)
2. Intrinsic (non-atopic)
What is extrinsic (atopic) asthma?
- hereditary predisposition to generate IgE in response to commonly encountered allergens in environment
- asthma usually begins in childhood
- may be history of eczema
What is intrinsic (non-atopic) asthma?
- causal agent not identified
- less frequent childhood
- rarely family history
- no hayfever, eczema or other allergic manifestations
What is a risk factor for asthma?
Risk factor relates to an entity that increases the likelihood of getting a disease or a condition
Significance of risk factors in asthma:
- asthma may develop with or without various risk factors
- greater number of risk factors > potential likelihood for developing asthma
Why is family history relevant in asthma?
genetic predisposition has been demonstrated
Which genes have been linked to asthma?
Recently 2 asthma genes have been identified:
- ADAM 33
- PH 11
Which chromosomes are linked to asthma?
5, 11, 12
Which infections are risk factors for asthma?
Upper respiratory tract infections:
- mainly viral
- RSV (respiratory syncytial virus)
What are some allergens that are risk factors for asthma?
Pollen, house dust mites, cockroaches, pets
What are some air pollutants that are risk factors for asthma?
particulates (PM10), ozone, nitrogen oxides, SO2
