2. Asthma
Asthma is disease of lower respiratory tract, also known
as Reactive Airway Disease. It is chronic inflammatory
disorder.
3. Some allergens which may cause
asthma
House-dust mites which live in
carpets, mattresses and
upholstered furniture
Spittle, excrements,
hair and fur
of domestic
animals
Plant pollen
Pharmacological agents
(enzymes, antibiotics,
vaccines, serums)
Food components
(stabilizers, genetically
modified products)
Dust of
book
depo-
sitories
5. Classification
Asthma can be divided into :
extrinsic - implying a definite external cause.
occurs most frequently in atopic individuals who
show positive skin-prick reactions to common
inhalant allergens ,+ve family history of allergy,
and usually high serum level of Ig E. Childhood
asthma is often accompanied by eczema. late-
onset asthma in adults is often due to
sensitization to chemicals or biological products
in the workplace, aspirin intolerance, or because
they were given β-adrenoceptor-blocking agents
for concurrent hypertension or angina.
6. Intrinsic asthma or cryptogenic - when no
causative agent can be identified often starts in
middle age ('late onset'). Family history of allergy
is often - ve ,and the serum level of Ig E is not
raised.
Extrinsic causes must be considered in all cases
of asthma and, where possible, avoided .
Etiology:
Asthma is a heterogeneous disease with interplay
between genetic and environmental factors. Several risk
factors have been implicated.
8. N.B: The term 'atopy' was used by clinicians at the beginning
of the century to describe a group of disorders, including
asthma and hay fever, that appeared:
I. To run in families
II. To have characteristic wealing skin reactions to common
allergens in the environment
III. To have circulating antibody in their serum that could be
transferred to the skin of non-sensitized individuals.
The term is best used to describe those individuals who readily
develop antibodies of IgE class against common materials
present in the environment. with many patients showing a
family history of allergic diseases.
9.
10. Pathology:
The airway mucosa is infiltrated with activated
eosinophils and T lymphocytes, and there is activation of
mucosal mast cells. The degree of inflammation is poorly
related to disease severity and may be found in atopic
patients without asthma symptoms.
Thickening of the basement membrane due to
subepithelial collagen deposition; it is likely to be a
marker of eosinophilic inflammation in the airway, as
eosinophils release fibrogenic factors.
The epithelium is often shed or friable, with reduced
attachments to the airway wall and increased numbers of
epithelial cells in the lumen. Metaplasia (stratified non
ciliated) may occur.
