Internal Medicine

0521779407-21 CUNY1086/Karliner 0 521 77940 7 June 7, 2007 18:59

1496 Urticaria (Dermatology)

■Nonimmunologic

➣Direct mast cell degranulators– e.g., opiates, polymyxin, tubocu-

rarine, radiocontrast dye

➣Indirect mast cell degranulators via arachidonic acid pathway

or kallikrein–kinin system alteration, e.g., aspirin, NSAIDs, tar-

trazine (yellow food dye), benzoate (food preservative)+

➣Angiotensin–converting enzyme (ACE) inhibitors

■Autoimmune

➣Due to histamine-releasing IgG autoantibodies to high-affinity

IgE receptors

➣Associated with Hashimoto’s thyroiditis, systemic lupus erythe-

matosus, vasculitis, and/or hepatitis

■Idiopathic –etiology indeterminable in over 50–75% chronic

urticarias

Signs & Symptoms

■Urticaria

➣Pruritic wheals appearing in crops that are transient and evanes-

cent (individual lesions resolve in <24 h)

■Angioedema

➣Nonpruritic, painful swelling of eyelids, mouth, distal extremities

➣May involve larynx, tongue and GI tract

■Urticarial vasculitis

➣Wheals last >24 h

➣Wheals heal with purpura or postinflammatory hyperpigmenta-

tion

➣+/−constitutional symptoms

tests

Provocative Testing for Suspected Physical Urticarias

■Dermatographism: stroke skin with firm pressure

■Pressure: apply 15 lb. weight for 20 minutes, inspect at 48 hours

■Solar: phototesting with UVL and fluorescent light

■Familial cold: expose to cold air for 20–30 minutes

■Acquired cold: plastic wrapped ice cube to skin for 5 minutes

■Cholinergic: exercise patient

■Aquagenic: 35◦C water compress to upper body skin for 30 minutes

■Vibratory: apply vortex vibration to forearm for 5 minutes

Laboratory

■Usually not necessary for acute urticaria (episodes <6 weeks)

■Basic: CBC with differential, ESR, urinalysis, LFTs

■Additional testing directed by history and physical exam