Erythema multiforme in Adult
In the past, the conditions EM, Stevens-Johnson syndrome (SJS), and toxic epidermal necrolysis (TEN) were considered a continuum, but EM is now considered a distinct hypersensitivity eruption that does not progress to SJS/TEN. It can be distinguished from SJS/TEN based on the presence of typical target lesions (as opposed to atypical targetoid lesions) and papular (rather than macular) lesions.
In adults, the primary trigger for EM is herpes simplex virus (HSV), which is estimated to incite about 90% of cases. Mycoplasma is another common trigger. In children, important additional triggers to consider include drugs (particularly penicillin), group A Streptococcus, and Epstein-Barr virus among other viruses and bacteria.
Typically, all cutaneous lesions appear within 24-72 hours and persist for 2 weeks before fading. The eruption recurs on repeated exposure to the inciting agent.
The following points should be kept in mind when a diagnosis of EM is being considered:
- Herpes labialis may precede, develop concomitantly, or manifest after the onset of EM. In almost half of all cases, herpes labialis precedes EM.
- Classical target lesions are well-defined circular lesions that are less than 3 cm in diameter, have 3 distinct color zones, and a central zone that has a bulla or crust.
- Atypical target lesions are palpable, poorly defined, circular lesions that have 2 distinct color zones. Raised atypical targets are a subtype of atypical targets that have a vesicle or bulla centrally.
- EM is not considered within the same disease spectrum as SJS/TEN and confers no risk in progressing to TEN.
- EM major refers to the presence of significant mucosal involvement in a case of EM, whereas in EM minor, mucosal involvement is absent or minimal.
L51.9 – Erythema multiforme, unspecified
22972008 – Erythema multiforme, dermal type
- Stevens-Johnson syndrome (SJS) / toxic epidermal necrolysis (TEN) – Histological features may not differentiate EM from SJS/TEN. Clinically, however, look for irregularly shaped, dusky red macular or patch-like lesions on the trunk, face, and palms / soles. A positive Nikolsky sign can be found; there is mucosal involvement, including the eyes, lips, mouth, and genitalia. Look for hemorrhagic crust, bullae, and denudation in these areas. Systemic symptoms are commonly present but not invariable. Lesions are more pronounced on the trunk than on the extremities. Precipitating factors are usually medications.
- Reactive infectious mucocutaneous eruption (RIME) – Usually occurs secondary to mycoplasma infection (as evidenced by clinical pneumonia, imaging studies, and/or mycoplasma serologies) although Chlamydia pneumoniae, human parainfluenza virus 2, rhinovirus, adenovirus, enterovirus, human metapneumovirus, and influenza B virus have more recently been recognized to cause a similar clinical picture. There is pronounced oral and ocular mucositis with absent, spare, or mild cutaneous involvement. Cutaneous lesions are most often tense vesiculobullae. Target or targetoid lesions may be present. Cutaneous lesions do not erode or desquamate as seen in SJS/TEN. (Note: erosion is seen in the genital and perianal skin, which are considered akin to mucosal surfaces.) Nikolsky sign is negative. Acute and convalescent mycoplasma titers may be employed to help to establish this diagnosis in the correct clinical scenario.
- Generalized fixed drug eruption – Look for erythematous plaques that develop on the lips, face, distal extremities, and genitalia 1-2 weeks after medication ingestions. Oral mucosa can be involved. Histology will differentiate fixed drug eruption from EM.
- Urticaria multiforme – New lesions appear daily; lesions are transient and last less than 24 hours, associated with edema of lips, face, hands, and feet. No evidence of epidermal damage in the center of urticarial lesions. Subcutaneous epinephrine injections will clear urticarial lesions but not EM lesions.
- Erythema annulare centrifugum (EAC) – Erythematous, annular patches and plaques that are idiopathic in nature; can last from days to months, no systemic symptoms, lesions commonly appear on hips and thighs. Biopsy will differentiate EAC and EM.
- Lichen planus – Very pruritic, sometimes associated with hepatitis C. Biopsy will differentiate EM from lichen planus.
- Subacute cutaneous lupus erythematosus (SCLE) – ANA will be positive in the majority of lupus patients. SCLE is characterized by annular plaques with raised borders and central clearing or papulosquamous lesions that are restricted to sun-exposed skin.
- Secondary syphilis – Scattered scaling papules and plaques; check rapid plasma reagin (RPR), check for history of primary chancre and systemic symptoms.
- Leukocytoclastic vasculitis (LCV) – Palpable purpura is the most common finding, consisting of nonblanching 1-3 mm, violaceous, round papules, characteristically involving the lower extremities. Biopsy will differentiate fixed LCV from EM.
- Arthropod bites – Haphazard distribution of erythematous papules.
- Viral exanthem
- Erythema nodosum
- Cocaine levamisole toxicity
- Kawasaki disease
- Autoimmune progesterone dermatitis
- Paraneoplastic pemphigus