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Toronto Notes 2019
Pediatric Exanthems
Dermatology D41
Pediatric Exanthems
• seePediatrics,P51
Miscellaneous Lesions
Angioedema and Urticaria
Angioedema
• deeperswellingoftheskininvolvingsubcutaneoustissues;ofteninvolvestheeyes,lips,andtongue • mayormaynotaccompanyurticaria
• hereditaryoracquiredforms
• hereditaryangioedema(doesnotoccurwithurticaria)
■ onset in childhood; 80% have positive family history
■ recurrent attacks; 25% die from laryngeal edema
■ triggers: minor trauma, emotional upset, temperature changes
• typesofacquiredangioedema
■ acute allergic angioedema (allergens include food, drugs, contrast media, insect venom, latex) ■ non-allergic drug reaction (drugs include ACEI)
■ acquired C1 inhibitor deficiency
• treatment
■ prophylaxis with danazol or stanozolol for hereditary angioedema
■ epinephrine pen to temporize until patient reaches hospital in acute attack
Urticaria
• alsoknownas“hives”
• transient,red,pruriticwell-demarcatedwheals
• eachindividuallesionlastslessthan24h
• secondmostcommontypeofdrugreaction
• resultsfromreleaseofhistaminefrommastcellsindermis • canalsoresultafterphysicalcontactwithallergen
Table 24. Classification of Urticaria
DDx for Urticaria
DAM HIVES Drugs and foods Allergic Malignancy Hereditary Infection Vasculitis Emotions Stings
Approach to Urticaria
• Thorough Hx and P/E
• Acute: no immediate investigations
needed; consider referral for allergy testing • Chronic: further investigations required:
CBC and differential, urinalysis, ESR, TSH,
LFTs to help identify underlying cause
• Vasculitic: biopsy of lesion and referral to
dermatology
Wheal
• Typically erythematous flat-topped, palpable lesions varying in size with circumscribed dermal edema
• Individual lesion lasts <24 h
• Associated with mast cell release of
histamine
• May be pruritic
Mastocytosis (Urticaria Pigmentosa)
Rare disease due to excessive infiltration
of the skin by mast cells. It manifests as many reddish-brown elevated plaques and macules. Friction to a lesion produces a wheal surrounded by intense erythema (Darier’s sign), due to mast cell degranulation; this occurs within minutes
Type
Acute Urticaria
>2/3 of cases
Attacks last <6 wk Individual lesions last <24 h
Chronic Urticaria
<1/3 of cases
Attacks last >6 wk Individual lesion lasts <24 h
Etiology
Drugs: especially ASA, NSAIDs Foods: nuts, shellfish, eggs, fruit Idiopathic
Infection
Insect stings (bees, wasps, hornets)
Percutaneous absorption: cosmetics, work exposures Stress
Systemic diseases: SLE, endocrinopathy, neoplasm
IgE-dependent: trigger associated
Idiopathic (90% of chronic urticaria patients)
Aeroallergens
Drugs (antibiotics, hormones, local anesthetics)
Foods and additives
Insect stings
Parasitic infections
Physical contact (animal saliva, plant resins, latex, metals, lotions, soap)
Direct mast cell release
Opiates, muscle relaxants, radio-contrast agents
Complement-mediated
Serum sickness, transfusion reactions
Infections, viral/bacterial (>80% of urticaria in pediatric patients) Urticarial vasculitis
Arachidonic acid metabolism ASA, NSAIDs
Physical
Dermatographism (friction, rubbing skin), cold (ice cube, cold water), cholinergic (hot shower, exercise), solar, pressure (shoulder strap, buttocks), aquagenic (exposure to water), adrenergic (stress), heat
Other
Mastocytosis, urticaria pigmentosa
Idiopathic
Infections
Hepatitis Autoimmune diseases SLE
Drug hypersensitivity Cimetidine and diltiazem
Urticarial Vasculitis
Individual lesions last >24 h Often painful, less likely pruritic, heals with bruise type lesions
Requires biopsy