Asthma (Etiology, Epidemiology, Pathology and Risk Factors) Flashcards
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
When is exercise a more common risk factor for asthma?
In children
- particularly in cold air
Which gender is at more risk of asthma?
Initially males > females
Later females > males
Which food and drinks may be risk factors for asthma?
Dairy products, alcohol, peanuts, various fruit juices
Which additives are risk factors for asthma?
Metabisulphate, tartrazine, monosodium glutamate
What are some work related risk factors for asthma?
Irritants and specific sensitizers
What are hormonal risk factors of asthma?
Premenstrual exacerbations, pregnancy
Regarding birth, what are some risk factors of asthma?
Low birth weight / pre-term delivery:
- birthweight <2.5kg or <37 weeks gestation
- small (or excessively “floppy”) airways
Which medical conditions are risk factors for asthma?
- rhinitis / sinusitis (“united airway”)
- obesity
- gastroesophageal reflux
Which drugs may be risk factors for asthma?
aspirin, NSAIDs, beta-blockers (including eye droppers), & as part of an anaphylactic response to other drugs
What are 2 other important risk factors for asthma?
- emotional stress
- smoking
What is occupational asthma?
Asthma caused by specific sensitizing agents inhaled in the workplace
= increasingly important
What is important in the consultation of a patient with suspected occupational asthma?
A detailed history:
- work-related symptoms
- typically improves at weekends & on holiday
- compensation
Occupational asthma: which occupation is associated with the following precipitant?
Isocyanates
Paint sprayers
Occupational asthma: which occupation is associated with the following precipitant? Animal proteins (e.g. excreta)
Laboratory workers
Occupational asthma: which occupation is associated with the following precipitant?
Reactive dyes
Manufacturing
Occupational asthma: which occupation is associated with the following precipitant?
Fungi
Brewers
Occupational asthma: which occupation is associated with the following precipitant?
Platinum salts
Platinum miners
Occupational asthma: which occupation is associated with the following precipitant?
Acid anhydrides
Manufacturing
Occupational asthma: which occupation is associated with the following precipitant?
Drugs and enzymes
Pharmaceutical workers
Occupational asthma: which occupation is associated with the following precipitant? Plicatic wood (Western Red Cedar)
Forestry workers
Occupational asthma: which occupation is associated with the following precipitant? Pinewood resin (colophony)
Joiners
Occupational asthma: which occupation is associated with the following precipitant?
Shellfish proteins
Seafood workers
What can be done to prevent asthma?
- avoid provoking factors where possible in predisposed individuals
- education of caregivers and patients
