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Urticaria（ 荨麻疹）. Fang Hong 方 红 Dermatology Department, The 1st Affiliated Hospital, Medical School, Zhejiang University. Definition. Urticaria is characterized by transient erythematous and edematous plaques (wheals) that are usually associated with pruritus. Wheal
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Urticaria（荨麻疹） Fang Hong 方 红 Dermatology Department, The 1st Affiliated Hospital, Medical School, Zhejiang University
Definition • Urticaria is characterized by transient erythematous and edematous plaques (wheals) that are usually associated with pruritus. • Wheal is theprimary lesion, which is defined as circumscribed, white to pink-colored, compressible skin elevation produced by dermal edema.
Urticaria Central pallor can be seen as in the wheal-and-flare reaction to histamine. The lesions vary in size and number and may assume a figurate or polycyclic configuration .
Acute versus ChronicUrticaria • All urticarias are acute initially. The duration of an individual lesion is usually a few hours and rarely greater than 24 hours; when the urticaria resolves, the skin is normal in appearance.Some will become chronic after a period of time that is usually defined as 6 weeks or more. • Acute: less than 6 weeks • Chronic: more than 6 weeks
Angioedema • Angioedema is a reflection of transient edema of the deep dermal, subcutaneous and submucosal tissues. • It is associated with urticaria In 50% of cases and may be complicated by life- threatening anaphylaxis.
Urticaria versus angioedema • Urticaria is characterized by transient skin or mucosal swellings due to plasma leakage. • Superficial dermal swellings are wheals, and deep swellings of the skin or mucosa are termed angioedema. • Wheals are characteristically pruritic and pink or pale in the center, whereas angioedema is often painful, less well defined and shows no color change.
Etiology Multiplicity of trigger factors • Infection:hepatitis B, hepatitis C, Helicobacter pylori, parasites, dermatophyte infections, sinusitis, and dental abscesses; • Drug intake: • Foods hypersensitivity:nuts, eggs, strawberries, tomatoes, chocolate, fish, and citrus fruits; • Exposure to inhalant allergens: • Others:spiritual trauma, specific external physical agent, insect bites, serum sickness, pregnancy.
Pathomechanisms • Idiopathic • Immunologic Autoimmune (autoantibodies against FceRI or IgE) IgE-dependent (allergic) Immune complex (vasculitic) Complement- and kinin-dependent (C1 esterase inhibitor de.ciency) • Non-immunologic Direct mast cell-releasing agents (e.g. opiates) Vasoactive stimuli (e.g. nettle stings) Aspirin, other non-steroidal anti-inflammatory drugs, dietary pseudoallergens Angiotensin-converting enzyme inhibitors
Pathomechanisms Immunologic mechanism of urticaria:When fixed by IgE antibodies bound to the surface of mast cells via the high-affinity receptor for IgE (FcεRI), antigens can induce mediator release in disorders such as allergic urticaria or allergic rhinitis. Autoantibodies (IgG1 and 3) binding to the Fc ε RI, activating complement (C) and releasing C5a may contribute to mast cell release.
Clinical features • Intense pruritus is the typical symptom of urticaria. Stinging and prickling sensations are also described. Pruritus is milder in angioedema because the edema occurs in deeper areas where there are fewer sensory nerve endings; • Urticarial whealsare raised, erythematous, and edematous plaques with sharply defined, serpiginous, or polycyclic borders surrounded by an erythematous halo. Intensely edematous lesions will have a blanched center. Their diameters may range from millimeters to several centimeters. Individual lesions last up to 8 to 12 hours (<24h); • Gastrointestinal or laryngeal signsmay accompany.
Physical Urticarias • The physical urticarias represent a distinct subgroup of the urticarias that are induced by an exogenous physical stimulus rather than occurring spontaneously.
Dermatographism • Dermographism is the most common of the physical urticarias . It manifests as linear wheals at sites of scratching and at other sites of friction, such as collars and cuffs of clothes.
Dermatographismmanifests as linear wheals at sites of scratching and at other sites of friction.
Cold urticaria • Cold urticaria represents a heterogeneous group of conditions in which whealing occurs within minutes of rewarming after cold exposure .
Cholinergic urticaria • This presents with multiple transient papular wheals 2–3 mm in diameter, surrounded by an obvious flare. They occur within 15 minutes of sweat-inducing stimuli, such as any form of physical exertion, hot baths, or sudden emotional stress.
Cholinergic urticaria on the trunk after exercising and sweating.
Diagnosis • Urticaria is a easily recognizable disorder; • Diagnosis is based primarily on the history and is supported by investigations, including blood tests, physical and dietary challenges, skin tests and skin biopsy. • Clinical findings: Episodic and evanescent wheals persist for less than 24 h , with multiple lesions occurring in various stages of evolution and resolution.
Treatment • 1.Eliminating the eliciting stimuli. • 2. Nonsedating second-generation H1 antagonists were recommended as standard and initial treatment: loratadine, cetirizine, mizolastine….. • 3. First-generation H1 antagonists • 4.oral corticosteroids as an alternative treatment.
