Snapshot A 25-year-old man presents with an itchy rash on his chest wall. He denies any exposures to insects and denies any previous allergies. He recently had an upper respiratory infection. Physical exam shows blanching, raised, edematous annular lesions that are well-circumscribed. Some lesions are coalesced. This is his first episode of this itchy rash. He denies any other symptoms. Introduction Pruritic inflammation of the skin commonly known as “hives” Characterized by superficial, localized edema and erythema Epidemiology most frequent dermatologic disorder seen in the emergency room Pathogenesis involving dermis and epidermis mast cell and basophil release of vasoactive substances histamine, bradykinin, and prostaglandins intense pruritus is from histamine in the dermis type I hypersensitivity reaction Triggers of acute urticarial (< 6 weeks) drugs food viral infection recent illness insect bite emotional stress cold or heat alcohol ingestion pregnancy exposure to other allergens (pet dander, dust, mold, or chemicals) sun Chronic urticarial is usually idiopathic (> 6 weeks) Etiology identified in 40-60% of acute cases and 10-20% in chronic cases Presentation Symptoms history of previous urticaria pruritus lasts a few hours resolves spontaneously Physical exam well-circumscribed erythema and edema on skin blanching, raised, and palpable wheals can occur on anywhere on the body dermotographism (urticaria from light scratching) indicates very sensitive skin Evaluation Labs or biopsy not indicated for acute urticarial unless diagnosis is unclear ↑ IgE For chronic or recurrent urticarial test ESR, TSH, and ANA Histology of lesion dermal edema lymphatic channel dilation Differential Diagnosis Hereditary angioedema Contact dermatitis Multiple insect bites Erythema multiforme Treatment If known, discontinue offending agent If concern for airway compromise epinephrine Anti-histamines second generation > first generation Prognosis, Prevention, and Complications Prognosis most resolve spontaneously Prevention avoid known triggers take second generation anti-histamine daily Complications life-threatening angioedema
QUESTIONS 1 of 3 1 2 3 Previous Next Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (M1.MK.14.28) A 35-year-old woman comes to see her primary care physician, because she is concerned about her skin. She states that she noticed a rash after recently starting a new medication. The rash appears as numerous pale, red, raised, itchy bumps on both of her legs, as seen in Figure A. What histologic pattern is most consistent with this patient's dermatologic condition? Tested Concept QID: 103821 FIGURES: A Type & Select Correct Answer 1 Dermal edema 57% (103/180) 2 Spongiosis 28% (50/180) 3 Hyperkeratosis 7% (12/180) 4 Acantholysis 1% (1/180) 5 Acanthosis 7% (12/180) M 1 Question Complexity E Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 1 Review tested concept (M1.MK.13.1) A 17-year-old female accidentally eats a granola bar manufactured on equipment that processes peanuts. She develops type I hypersensitivity-mediated histamine release, resulting in pruritic wheals on the skin. Which of the following layers of this patient's skin would demonstrate histologic changes on biopsy of her lesions? Tested Concept QID: 101309 Type & Select Correct Answer 1 Stratum corneum 18% (52/282) 2 Stratum granulosum 17% (48/282) 3 Stratum spinosum 12% (35/282) 4 Stratum basale 9% (24/282) 5 Dermis 42% (119/282) M 1 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 5 Review tested concept