PANCE Blueprint Dermatology (5%)

Erythema multiforme (ReelDx)

REEL-DX-ENHANCED

Erythema Multiforme

Patient will present as → a teenager with bilateral symmetrical red papular rash with many target lesions confined to both lower limbs of one-week duration. The rash appeared 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.
  • Erythema multiforme is divided into major and minor forms and is now regarded as distinct from Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN).
  • Infections are associated with at least 90% of cases of erythema multiforme - most commonly HSV

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.

Treatment of any underlying or causative disease

  • Withdrawal of any drugs that might be the cause
  • Symptomatic treatment with oral antihistamines and topical corticosteroids for mild cases; mouthwashes or topical steroid gels for oral disease
  • 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
  • Prednisone for severe cases.
Erythema multiforme

Erythema multiforme

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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