Updated: 11/16/2018

Urticaria

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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
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Questions (3)
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(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:
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 E

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(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
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 D

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Topic COMMENTS (9)
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