Chapter 6: Urticaria and Angioedema Flashcards
(92 cards)
What percentage of the population will have at least one episode of Urticaria?
20%
What length of time defines chronic urticaria?
Six weeks
What is the likelihood of determining the cause of urticaria
high probability for acute urticaria
Only 5 to 20% of the cases of chronic urticaria
what is a hive or wheal
a circumscribed, erythematous or white, non-pitting, edematous, usually pruritic plaque that changes in size and shape by peripheral extension or aggression during the few hours or days that the individual lesion exist.
The eczematous, central area (wheal) can be pale in comparison to the erythematous surrounding area (flare)
what is a major difference between hives and angioedema
angioedema is deeper than hives
angioedema without urticaria may suggest what
may indicate a C1 esterase inhibitor deficiency
what is the most important mediator of urticaria
histamine
what happens when the H1 receptors are stimulated by histamine
an axon reflex, vasodilation, and pruritus
what happens when H2receptors are stimulated
vasodilation occurs
H2receptors are also present on the mast cell membrane surface and, when stimulated, further inhibit the production of histamine.
What is a common cause of acute urticaria?
Histamine release that is induced by allergen (drugs, foods or pollens) and mediated by IgE is a common cause of acute urticaria, and particular attention should be paid to these factors during the initial evaluation.
What plays a key role in infantile urticaria?
Food origin is important. in one series it accounted for 62% of patients, more than drug etiology of 22%.
what type of hypersensitivity is associated with most cases of acute urticaria?
Type I.
What causes the histamine release of the type I hypersensitivity reaction?
Circulating antigens such as foods, drugs or inhalants interact with cell membrane-bound IgE to release histamine.
Food allergies are the most common cause of anaphylaxis.
What is an Arthus reaction?
Type III hypersensitivity reaction
Occurs with deposition of insoluble immune complexes in vessel walls. These complexes Are composed of IgG or IgM with an antigen such as a drug.
Complement-mediated acute urticaria can be precipitated by administration of whole blood, plasma, immunoglobulins, and drugs or by insect stings.
What causes the urticaria in a type III hypersensitivity reaction.
Urticaria occurs when the trapped complexes activate complement to cleave anaphylotoxins C5a and C3a from C5 and C3. C5a and C3a are potent releasers of histamine from mast cells.
What are some non-immunologic mediators that cause the release of histamine
pharmacologic mediators, such as acetylcholine, opiates, polymyxin B, and strawberries, react directly with the cell membrane bound mediators to release histamine.
What is the pathogenesis of chronic urticaria?
Cutaneous mast cell release of histamine.
True or false:
over 30% of chronic urticaria patients have an autoimmune phenomena
true
Positive autologous serum skin test, antibodies to the alpha subunit of the basophil IgE receptor and to IgE, and thyroid autoimmunity.
Be sure to rule out physical urticaria.
what is the differential diagnosis of chronic urticaria
- Cutaneous lupus erythematosus
- Urticarial Vasculitis
- Urticaria pigmentosa
- Sweet’s syndrome
- Fixed drug eruption
- Bullous pemphigoid
- Muckle-Wells Syndrome (urticaria-deafness-amyloidosis syndrome)
- Chronic infantile neurologic cutaneous articular syndrome (neonatal onset multisystemic inflammatory disease)
- Schnitzler’s syndrome
should a biopsy taken of the urticarial plaque?
Yes. Patients with hives that are characteristic of urticarial vasculitis should have a biopsy taken of the urticarial plaque.
These hives burn rather than hitch and last longer than 24 hours.
what is the first-line treatment of urticaria
Non-sedating H1 antihistamines (Allegra 180 mg daily)
H2 receptor antagonist have few side effects and may be useful as an adjunct to therapy
Patients who have no response to any of these approaches may respond to immunotherapy with 200 to 300 mg of cyclosporine per day
what is the mechanism of action of antihistamines for the treatment of urticaria?
Antihistamines control urticaria by inhibiting vasodilation and vessel fluid loss.
Antihistamines do not block the release of histamine. If histamine has been released before anti-histamine is taken the receptor sites will be occupied in the antihistamine will have no effect
in addition to anti-histamines, what is an adjunct of therapy that can be used to treat urticaria in the anxious or depressed patient?
Doxepin
Initial dose is 10 to 25 mg. Gradually increased does up to75 mg for optimal control
what side effects are associated with antihistamines
antihistamines are structurally similar to atropine; therefore the produce atropinelike peripheral and central anticholinergic effects such as dry mouth, blurred vision, constipation, dizziness