Topic 20. Urticaria

7/28/2019 Topic 20. Urticaria

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Efi. Gelerstein 2011

Topic 20. Urticaria

Urticaria (hives) is one of the most frequent dermatological disorders.

It appears as well circumscribed area of erythema, involving the epidemis and dermis Pink, itchy or burning swelling (wheals) that can occur anywhere on the body. Individual lesions disappear after 24 hours (if not, more likely urticaria vasculitis) Acute, intermittent and Chronic (>6 weeks) forms

Angioedema is the rapid swelling of dermis, SQ, mucosa and submucosa (differs from urticaria thatoccurs only in upper dermis)

Pathophysiology Mediators of hives and swelling1. Mast cells Histamine, PG D2, LT C and D, Platelet activating factor2. Complement anaphylatoxins C3a, C4a, C5a, histamine3. Bradykinin4. Mononuclear cells histamin releasing factors, chemokines

Major causes of urticaria and angioedema

1. Drug cause mast cells to release histamine (aspirin etc)2. Food, food additives3. Inhalation, ingestion or contact with Ag4. Transfusion5. Infections6. Insects7. Collagen vascular diseases: cutaneous vasculitis, se. sickness8. Malignancy (aquired C1 inactivator depletion)9. Urticaria pigmentosa: systemic mastocytosis10.Hereditary angioedema, Familial cold urticarial

Food allergy1. GI Diarrhea, N&V, abd. pain2. Skin Urticaria, Eczema, Angioedema3. AW Rhinitis, Bronchitis, Asthma

Cows milk allergy

1. Allergens caseins1. -lactoglobulin2. -lactalbumin

2. Symptoms1. Gastrointestinal2.

Skin pruritus, urticaria, eczema3. Airway symptoms rhinitis, asthma

3. IgE mediated

major allergen

The 10 Is of Ag encounter inHS urticaria.

1. Ingestion2. Inhalation3. Instillation4. Injection5. Insertion6. Insect bites7. Infestations8. Infection9. Infusion10.Inunction (contact)


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Wheat allergy

1. Coeliac Permanent, gluten-sensitive enteropathy Rice, maize gliadin-free HLA-B8 and HLA-Dw3 associated T-cell mediated mucosal atrophy

2. Dermatitis herpetiformis Gluten-sensitive enteropathy Characteristic skin lesions Linear IgA deposition at the BM Mucosal atrophy

3. Short course wheat allergy w/o GI symptoms, urticaria, vasculitisPhysical urticaria

Cold in areas exposed to cold Solar in areas exposed to sun Heat areas after contact with hot objects or solutions Cholinergic Anxiety, heat, sexual excitement or strenuous exercise Dermographism (immediate pressure urticaria) after rubbing / scratching Delayed pressuresustained pressure causes oedema of the underlying skin and subcutaneous

tissue 3-6 h later.

Bee-, wasp venom allergy

Severe anaphylaxis, develops in minutes Quincke Edema (Angioedema)

Insect bites allergy

Toxic and allergic reactions Venom contains

1. Vasoactive amines2. Enzymatic peptides3. Free amino acids

Specific immunotherapyHereditary angioedema (HANO)AD inheritance, recurrent attacks of abd. pain, massive edema of soft tissues

Absence of C1 esterase inhibitor C4 is diminished even without symptoms

Normal or C1 INH level: dysfunctional protein Complement, plasma kinin forming pathway are involved Therapy danazol, stanozolol (androgens induce synthesis of C1 INH and C4 level),

aminocaproic acid,

In acutecases fresh frozen plasma, C1INH injection (Benedril)


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Autoimmune urticaria

Autoimmune disease with IgG antibodies to IgE or toFcIgE receptors on mast cells

AutoAB act as antigens to trigger mast celldegranulation

Presentation Sudden appearance of pink itchy wheals Anywhere on the skin surface Lasts for < day, and most disappear within a few

hours.

Acute anaphylactic reaction wheals may covermost of the skin surface.

Chronic Urticaria only a few wheals may developeach day.

Course

The course of an urticarial reaction depends on its cause. Allergic will continue until the allergen is removed, tolerated or metabolized. Triple response of Lewis erythema, edema, axon reflex

Complications

Urticaria is normally uncomplicated, although its itch may be enoughto interfere with sleep or daily activities and to lead to depression.

In acute anaphylactic reactions, edema of the larynx may lead to asphyxiation, and edema oftracheobronchial tree may lead to asthma

Differential diagnosis

Other eruptions that are not urticaria at all Define the type of urticaria (Drugs, both topical and systemic, Foods and food additives, Bites,

Inhalants, Pollens, Insect venoms, Animal dander)

Erythema multiform can mimic an annular urticaria. Urticarial vasculitis may resemble urticaria, but individual lesions last for longer than 24 h and may

leave bruising in their wake

Investigation

Depend upon the presentation and type of urticaria. History should include details of the events surrounding the onset of the eruption. Careful attention to drugs OTC (aspirin / herbal) and medications given by other routes (10 Is). In acute urticaria with unknown cause investigations are often delayed until it has persisted for a

few weeks.

- Screening tests such as a CBC, ESR, routine biochemical screen, chest X-ray and urine analysisare worthwhile.

- If urticaria continues for 2-3 months dermatologist.In some patients with acute or contact urticaria, allergy testing in the form ofRAST orprick tests, usingonly allergens suggested by the history, can sometimes be of help.


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RAST test is a radioimmunoassay test to detect specific IgE antibodies to allergens.

The suspected allergen is bound to an insoluble material patient's serum is added. If the serum contains ABs to the allergen ABs bind to allergen Radiolabeled anti-human IgE

ABs is added binds to IgE ABs already bound unbound anti-human IgE ABs washed away.

The amount of radioactivity is proportional to the serum IgE for the allergen. More expensive then prick tests but pose NO risk of anaphylaxis.

Prick testing

It detects immediate (type I) HS Patients should not have taken systemic antihistamines for at least 48 h before the test. Commercially prepared diluted antigens and a control are placed as single drops on marked areas of

the forearm skin is gently pricked through the drops drops are then removed with a tissue wipe.

After 10 min the sites are inspected and the diameter of any wheal measured and recorded. (+) result = a wheal of 4 mm or greater and the control elicits negligible reaction. Positive results should correlate with (+) radioallergosorbent tests (RAST).

Treatment:

Find and eliminate the cause Antihistamines Cetirizine, Loratadine (10 mg/day), Hydroxyzine (shorter acting) During pregnancy Chlorpheniramine / diphenhydramine.

Type Treatment

Cold urticaria Avoid cold Protective clothing Terbutaline (2.5 mg every 8 h) + aminophylline

Solar urticaria Avoid sun exposure / Protective clothing

Beta-carotene and AntihistaminesCholinergic urticaria

Avoid heat Minimize anxiety and Avoid excessive exercise Anticholinergic and Antihistamines

Dermographism Avoid trauma Antihistamines

Hereditary angioedema Avoid trauma Attenuated androgenic steroids as prophylaxis (cyclosporine) Tracheotomy may be necessary

Hypersensitivity urticarias

Remove cause Antihistamines H1+H2 (cimetidine) Sympathomimetic, avoid aspirin-containing drugs.

Topic 20. Urticaria

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