Urticaria

Drug-induced urticaria is the most common form of urticaria in children; anaphylaxis and hereditary angioedema are life-threatening conditions; remember ABCs of resuscitation (airway, breathing, circulation); best treatment is prevention; that is, avoidance of causative agents.

Differential Diagnosis

• Urticaria
  –Epidemiology: Lifetime incidence 20%; most cases resolve within 48 hours; chronic >6 weeks
  –Pathophysiology: Hypersensitivity reaction: allergens (IgE-mediated, prior sensitization), complement, and other cytokines activate mast cells and basophils to release histamine (also kinins, prostaglandins, serotonin) with plasma extravasation; wheals/hives: dermis edema
  –Triggers: Most cases are idiopathic
  –IgE-mediated: Insects (bees, wasps, scorpions, spiders, jellyfish), foods (eggs, shellfish, tree nuts, peanuts, tomatoes), drugs (penicillins, cephalosporins, NSAIDs, barbiturates, amphetamines, insulin, blood products), pollen, danders, food additives
  –Non-IgE-mediated: Infections (strep, EBV; hepatitis A, B, and C; adenovirus, enterovirus; fleas, mites), drugs (opiates, acetylsalicylic acid, local anesthetics), physical (exercise, cold/heat, UV light, water, pressure), contrast dyes, latex

• Chronic urticaria: Associated with collagen vascular diseases (SLE, cryoglobulinemia), inflammatory bowel disease, malignancy, thyroiditis, hyperthyroidism, Behçet disease, vasculitis
• Angioedema: 50% of urticaria cases; subcutaneous and mucous membrane edema
• Anaphylaxis (IgE-mediated)
  –Most potent foods: Peanuts, fish
  –Mortality: 100–500 deaths/year in U.S.
  –Associated shock has a poor prognosis
• Hereditary angioedema
  –High mortality
  –Most cases are autosomal dominant
  –C1 esterase inhibitor deficiency
  –Recurrent episodes of edema (face, upper airway, extremities)
  –Triggers: Trauma, surgery
  –Unresponsive to epinephrine, antihistamines
• Others: Erythema multiforme, mastocytosis, guttate psoriasis, flushing, cellulitis

Workup and Diagnosis

• History: Exposure to triggers, associated symptoms, symptoms of hypo-/hyperthyroidism, “feeling of impending doom” (anaphylaxis), history of atopy, family history of systemic diseases

• Physical exam
  –Wheals/hives: Transient, elevated, erythematous, severely pruritic plaques, sudden onset; each wheal lasts 30 minutes to 3 hours, reappearing in other areas
  –Papular uritcaria: 2–3 mm red papules surrounded by 10–20 mm wheals, most common in toddlers, due to fleas and mites (e.g., scabies)
  –Physical urticaria: 10–20 mm erythematous macules with central wheal
  –Angioedema: Edema of face, hands, feet, genitalia
  –Anaphylaxis: Irritability, wheals, broncho- or laryngospasm (wheezing/stridor), angioedema, hypotension (late finding in children), vomiting, bloody diarrhea, mental status change; develops over minutes to hours; may develop DIC
  –Hereditary angioedema: Nonpruritic edema

• Labs/studies
  –Urticaria/anaphylaxis: IgE antibody skin test or radioallergosorbent test for IgE-mediated causes; culture, microscopy (ova and parasites)
  –Angioedema: C1 esterase inhibitor, C3, C4
  –Chronic urticaria: ANA, urinalysis, CBC, CRP, ESR, thyroid antibodies

Treatment

• Urticaria: Antihistamine; if nonresponsive to antihistamine or chronic uritcaria, then use corticosteroids
• Severe angioedema/anaphylaxis: ABCs of resuscitation
  –Epinephrine: 1:1,000, 0.01 mg/kg SC (1:10,000 IV/IO if in shock), every 15 minutes up to three doses, maximum cumulative dose: 0.3 mg (child), 0.5 mg (adult)
  –IV fluids if hypotension
  –Nebulized Albuterol; antihistamine; corticosteroid (for late phase)
  –Observation: Mild, 2–4 hrs; severe, 12–24 hours
  –Consult pediatric allergist
  –Give patient EpiPen for self-administration
• Hereditary angioedema
  –C1 esterase inhibitor concentrate; adults, danazol
• Avoid exposure to causative agents
• Desensitization to insect venoms
• Treat underlying disorders

Book Source Details

• Book Title: In A Page: Pediatric Signs and Symptoms
• Author(s): Jonathan E. Teitelbaum, Kathleen O. Deantonis, Scott Kahan
• Year of Publication: 2007
• Copyright Details: In A Page: Pediatric Signs and Symptoms, Copyright © 2007 Lippincott Williams & Wilkins.

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More About This Book: Title: In A Page: Pediatric Signs and Symptoms Authors: Jonathan E. Teitelbaum, Kathleen O. Deantonis, Scott Kahan Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 1-4051-0427-9