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: causes widespread skin lesions and affects 2 + mucosal sites
- Minor: affects a limited region of the skin and 1 type of mucosa (usually oral)
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 the 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
- backs of hands and feet
- extensor aspects of forearms and legs
- Must also examine mucosal surfaces and eyes
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)
- 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
Dome-shaped, waxy, umbilicated papules
Describes Molluscum contagiosum
Silvery scales on well-demarcated erythematous plaques
Pruritic coin-shaped plaques or grouped vesicles with an erythematous base typically occurring during the cold seasons
Target lesion with variable mucous membrane involvement
Are the most common drug triggers.
Can trigger erythema multiforme minor, but are not the most common cause.
Herpes simplex virus
A common cause, but not the most common.