october 27, 2011 good morning! welcome applicants!
TRANSCRIPT
Differential Diagnosis of Urticaria
Viral exanthem
Atopic dermatitis
Contact dermatitis
Toxic drug eruption
Insect bites
Bullous pemphigoid
Erythema multiforme
Plant induced reactions
Cutaneous small vessel vasculitis
Pityriasis rosea (early lesions)
Mastocytosis
URTICARIA
• Urticaria – intensely pruritic, erythematous plaques that appear over the course of minutes, enlarge and coalesce with other lesions, then disappear within a few hours• Acute = new onset; present less than 6 weeks• Chronic = occurring most days of the week for >6 weeks;
1/3 of acute will become chronic• Papular• Physical (cholinergic, dermatographism)
• Angioedema – can accompany urticaria• Swelling deeper in the skin
EPIDEMIOLOGY
• Affects 20% of people at some point in life• 3% of preschool children• 2% of older children
• Fever than 5% have documented IgE-mediated allergic urticaria
• 15% have physical urticaria
• Most fall into “idiopathic” group• No specific cause is found in most cases
PATHOGENESIS
• Histamine is the primary mediator• Released directly from cutaneous mast cells in response to certain foods or drugs
• Complement fragments (activated by immune complexes) may activate mast cells to release histamine or exert direct vasoactive effects on cutaneous blood vessels• Papular urticaria – basophilic infiltrate; delayed
hypersensitivity• Physical urticarias – neuropeptide mediated
ETIOLOGIES
IgE-Mediated, Type I Reaction Direct Mast Cell Activation
Medications Narcotics
Stinging insects Muscle relaxants
Foods and food additives Vancomycin
Aeroallergens Radiocontrast
Contact allergens Tomatoes
Blood products Strawberries
Stinging nettle plant
CLINICAL MANIFESTATIONS
• Sudden in onset, pruritic, characterized by red raised 2- to 15-mm flat-topped wheals scattered over the body
CLINICAL MANIFESTATIONS
• Wheals commonly last from 20 minutes to 3 hours and then disappear, and reappear in other areas
• An entire episode of transient urticaria often lasts 24 to 48 hours• Rarely as long as 3 weeks
• Labs are typically normal• Consider CBC, UA, ESR, LFTs to detect underlying disorder
in the 30% of pts. that will progress to chronic
ANGIOEDEMA
• Subcutaneous extension of lesions• Large swellings that have indistinct borders
around the eyelids and lips• May also appear on the face, trunk, genitalia, and
extremities• Face, hands, and feet in 85%
• 50% of children with urticaria will have angioedema
PAPULAR URTICARIA
• Grouped on exposed areas• Last for 10 to 14 days• 10- to 20-mm wheal
surrounding a 2- to 4-mm red papule• Usually the result of an
encounter with animal fleas or mites• Difficult to convince
parents of etiology when whole family exposed
MANAGEMENT
• 2/3 cases are self-limited and resolve spontaneously
• H1 antihistamines• Second generation agents• Minimally sedating, free of anticholinergic effects• *First line therapy• Cetirizine, Levocetirizine, Loratadine, Desloratadine,
Fexofenadine
• First generation agents• More sedating, anticholinergic side effects• Helpful at bedtime• Diphenhydramine, hydroxyzine
MANAGEMENT
• H2 antihistamines• Combined with H1 may be more effective for acute
urticaria• Ranitidine, nizatidine, famotidine, cimetidine
• Glucocorticoids• A brief course (a week or less) added to antihistamines
may help gain control of symptoms• Do not inhibit mast cell degranulation, but suppress a
variety of inflammatory mechanisms• Appears to be helpful, but may not be necessary
PROGNOSIS
• An extensive allergy evaluation is not indicated for children with acute urticaria• An evaluation of chronic urticaria should be guided by
history
• Papular urticaria• Hypersensitivity to ectoparasites declines after 6 to 12
months, and the child may no longer be sensitive, even while still exposed
• Physical urticarias are more persistent• Last 2 to 4 years, or into adulthood