Allergic rhinitis

Question 1

pathogenesis of allergic rhinitis?

Answer 1

Pathogenesis : (Type I hypersensitivity reaction) :
1- When the patient exposed to the antigen, the body produces IgE.
2- IgE + mast cells (in nasal mucosa) → mast cell bound IgE.
3- Antigen + mast cell bound IgE → rupture of mast cell with release of
chemical mediators as histamine, serotonin, prostaglandins and
leukotrienes. These mediators will act on :
* Nerve ending causing itching and sneezing.
* Smooth muscles causing bronchospasm.
* Seromucinous glands causing increased secretions (rhinorrhea).
* Blood vessels causing vasodilatation (congestion) and increased
capillary permeability (oedema).
* Eosinophilic infiltrate.

Question 2

what is the etiology of allergic rhinitis?

Answer 2

Etiology :
* Predisposing factors :
- Positive family history.
- Psychogenic. - 328 -
- Physical factors e.g. changes in temperature and humidity.
- Infection which decrease tissue resistance.
* Precipitating factors : Exposure to allergens which may be - Inhalant : the commonest. It may be :
a- Seasonal as pollens, grasses and moulds.
b- Perennial as house dust, dust mite, animal dander and feather.
- Ingestant as egg, milk and wheat.
- Injectant as penicillin.
- Contactant : as face powders.
- Infectants : parasites end fungi.

Question 3

clinical picture of allergic rhinitis?

Answer 3

Clinical picture :
* Paroxysmal attacks of prolonged sneezing, profuse watery rhinorrhea
and nasal obstruction.
* Anosmia or hyposmia
* Palatal itching.
* Allergic conjunctivitis and bronchial asthma may be associated.

Question 4

what are the investigations of allergic rhinitis?

Answer 4

Investigations :
A- To confirm the diagnosis :
* Microscopic examination of a nasal smear → excess eosinophils.
* Blood examination : eosinophilia and increased total plasma IgE level.
B- To define the offending allergen :
* Nasal provocation tests.
* Skin sensitivity tests.
* Radio-allergo-sorbent test (RAST) to detect plasma IgE to a specific
allergen.
C- To detect complications :
* CT scan for paranasal sinus to detect sinusitis or polypi.

Question 5

explain treatment of allergic rhinitis

Answer 5

Treatment :
A- Prophylaxis :
* Avoid antigens exposure when the antigen is known.
* Zaditen or sodium cromglycate (stabilize mast cells prevents their
degranulation).
B- Medical :
* Antihistamine : local or systemic.
* Steroids : local or systemic.
* Immunotherapy (desensitization) by using small repeated doses of
the antigen. It is useful in seasonal allergy (grass pollen) but
anaphylaxis may occur.
C- Surgical (in resistant cases): (to relieve nasal obstruction)
* Polypectomy.
* Turbinate reduction surgery.