Urticaria: Factori și Mecanisme

Urticaria

• Urticaria is a multifactorial disorder, manifesting with urticarial papules and plaques often with an itchy sensation.
• Cutaneous lesions, including wheals and plaques, result from increased vascular permeability due to the action of numerous mediators, notably histamine.
• Urticaria mechanisms include immunological (e.g., type I anaphylactic reactions, type III immune complex reactions) and non-immunological (e.g., direct histamine release, non-immunological complement activation, mediator inhibitor deficiency, cholinergic mechanisms).
• Symptoms include itchy, transient, wheal-and-flare skin lesions (plaques and wheals), which typically disappear within hours.
• Persistent urticaria (lasting more than 24 hours) may indicate other skin conditions, like polymorphic erythema.
• Urticarial lesions do not leave visible marks on the skin.
• Lesions frequently appear in areas with loose connective tissue (e.g., lips, eyelids, genitals), presenting as soft, diffuse edema.
• Skin lesions might also be found on palms, soles, or the scalp as small, pruritic papules.
• Mucosal involvement may produce difficulty swallowing or talking.

Urticaria Classification

• Acute: Typically lasts 4–7 days, at most 3 weeks.
• Subacute: Recurrent episodes with intervals longer than the duration of each episode.
• Chronic: Lasting over 6 weeks, or characterized by recurring episodes at intervals of a month or more over a 6-month period.

Etiologies

• Common: Food (e.g., nuts, peanuts, chocolate, seafood, dairy products, pork, citrus fruits), medications (e.g., penicillins, NSAIDs, barbiturates), infections (e.g., viral infections like hepatitis B, HIV infection).
• Other: Insect bites or stings, physical stimuli (e.g., cold, heat, pressure, exercise), contact allergens.

Physical Urticaria

• Dermographism: Urticarial wheals/erythema develop after the skin is rubbed or scratched.
• Solar: Urticarial wheals/erythema appear within minutes after sun exposure.
• Heat: Skin lesions develop in response to heat or hot environments.
• Cold: Urticarial papules and erythema form on tissues exposed to cold.
• Pressure: Skin lesions develop after sustained contact pressure.

Other Types of Urticaria

• Contact: Skin response, in some, is triggered by direct contact with a substance.
• Symptomatic: Urticaria appearing as a result of underlying diseases (e.g., lupus, hepatitis, malignancies).
• Idiopathic: Urticaria with an unknown cause.

Morphology

• Color: Skin lesions can vary in color (e.g., red/pink (rubra), white (porcellanea), purple (purpuric)).
• Size: lesions can vary from small papules to large plaques.
• Shape: Lesions can be round, oval or have a specific pattern.
• Associated lesions: Different forms of lesions may be present, including bullous, hemorrhagic, pseudo-phlegmonous, or gangrenous forms.