PANCE Blueprint Dermatology (5%)

Erythema multiforme (ReelDx)

REEL-DX-ENHANCED

Erythema Multiforme

Patient will present as → a 15-year-old complaining of several red lesions on her palms, back of hands, and on her lips of one-week duration. On examination, you note a symmetrical red papular rash with many target lesions.  The rash appeared just a few days after herpes facialis.

Erythema multiforme (EM) is an acute, self-limited, and sometimes recurring skin condition that is considered to be a type IV hypersensitivity reaction associated with certain infections - most commonly herpes simplex virus (HSV), medications (sulfa drugs), and other various triggers.

  • Skin lesions predominantly involving the extremities (hands, feet, and mucosa)
  • Target-like shape, raised, blanching, and lack of itchiness help characterize this rash
  • Divided into erythema multiforme (EM) major and minor and is now regarded as distinct from Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN), which is a more severe mucocutaneous reaction that is usually caused by a medication
    • major: involves mucous membranes and systemic signs
    • minor: no mucous membrane involvement and no systemic signs

Causes: Infections are associated with at least 90% of cases of erythema multiforme - most commonly HSV

  • Most common = infection, Herpes simplex, Mycoplasma pneumonia, upper respiratory infections. Less common = drugs (e.g., sulfonamides, β-lactams, phenytoin). Often idiopathic.

EM may appear similar to Steven Johnson Syndrome (SJS) but SJS has a more generalized distribution of lesions; concentrated on the trunk (EM extremities and mouth), an absence of raised typical target lesions and atypical flat (not raised) target lesions or macules with coalescence of lesions.

Diagnosis is based on absent or mild prodromal symptoms, preceding HSV infection (up to 50% of cases) 10–15 days before the skin eruptions and a rash involving the skin and sometimes the mucous membrane, most commonly the mouth.

Presents as raised (papular), target lesions with multiple rings and dusky center (as opposed to annular lesions in urticaria)

  • Three concentric zones of color from center to outer ring
    • central dusky/dark area that can be crust or vesicle
    • paler pink or edematous zone
    • peripheral red/dark ring
  • Fixed lesions (as opposed to urticaria, in which lesions typically resolve within 24 hours)
  • Negative Nikolsky sign (as opposed to SJS/TEN)
  • Generally mild burning or itchiness; nontender
  • Most commonly involves
    • palms/soles
    • backs of hands and feet
    • extensor aspects of forearms and legs
  • Must also examine mucosal surfaces and eyes
    • oral
    • genital/anal
    • iris

Symptomatic treatment with oral antihistamines and topical corticosteroids for mild cases; mouthwashes or topical steroid gels for oral disease.

EM major (involvement of mucous membranes and systemic signs)

  • Corticosteroids
  • Ophthalmology consult if ocular involvement

EM minor (no mucous membrane involvement and no systemic signs) is usually self-limited

  • Supportive care

Early treatment with acyclovir may lessen the number and duration of cutaneous lesions for patients with coexisting or recent HSV infection.

  • Acyclovir for adults: 200 mg, 5× a day for 7–10 days in the onset of EM
  • For pediatric patients: 10 mg/kg/dose TID for 7–10 days

Typical target lesions of EM. Note the three zones of color.

Question 1
Which of the following best describes erythema multiforme?
A
Dome-shaped, waxy, umbilicated papules
Hint:
Describes Molluscum contagiosum
B
Silvery scales on well-demarcated erythematous plaques
Hint:
Psoriasis
C
Pruritic coin-shaped plaques or grouped vesicles with an erythematous base typically occurring during the cold seasons
Hint:
Nummular eczema
D
Target lesion with variable mucous membrane involvement
Question 1 Explanation: 
Erythema multiforme presents as target lesion with variable mucous membrane involvement.
Question 2
The most common cause of erythema multiforme minor is
A
Sulfonamides
Hint:
Are the most common drug triggers.
B
Fungal infections
Hint:
Can trigger erythema multiforme minor, but are not the most common cause.
C
Herpes simplex virus
D
Mycoplasma species
Hint:
A common cause, but not the most common.
Question 2 Explanation: 
Herpes simplex virus is the most common cause of erythema multiforme minor. Approximately 90% of cases of erythema multiforme minor follow outbreaks of herpes simplex.
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Desquamation (PEARLS) (Prev Lesson)
(Next Lesson) Stevens-Johnson syndrome
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