Erythema multiforme major

EM major · erythema multiforme · EM · target lesions · iris lesions

Target lesions on the limbs with mucosal erosions - usually herpes-driven, and not the same disease as SJS.

URGENT DERMBand A

Red flags

Extensive mucosal involvement preventing eating, drinking or passing urine
Ocular involvement - same-day ophthalmology
Truncal onset, dusky flat macules, detachable epidermis or a positive Nikolsky sign - this is epidermal necrolysis, not EM major, and the destination is different
A new drug in the preceding weeks with fever and mucosal erosions - again, reconsider epidermal necrolysis
Systemic upset, dehydration, or respiratory symptoms suggesting mycoplasma

Recognise

On light skin

Typical targets: a dusky or blistered centre, a paler oedematous middle ring, and a sharply defined red outer ring, raised and palpable, distributed acrally and symmetrically.

On brown and black skin

The three-zone target that defines the lesion is described entirely in colour, and in brown and black skin the outer ring may be violaceous, hyperpigmented or invisible, so the diagnosis is frequently delayed or missed. Rely on the architecture rather than the colour: run a finger over the lesion, because the concentric zones can be felt as a raised oedematous ring around a flatter, sometimes blistered, centre. The acral symmetrical distribution and the mucosal erosions are tone-independent. Resolution leaves prominent and long-lasting post-inflammatory hyperpigmentation, which is a common reason for re-presentation and is not active disease.

In any skin tone

Raised, palpable target lesions with concentric zones - palpate, do not only look
Acral, symmetrical distribution spreading inwards, unlike the truncal onset of SJS/TEN
Mucosal erosions, most often the lips and mouth, define the major form
A preceding cold sore or herpes simplex infection in most cases, and mycoplasma in children
Usually a drug is NOT the cause, which is the practical difference from epidermal necrolysis
In the consensus classification the deciding word is localised versus widespread: bullous erythema multiforme is localised typical or raised atypical targets with under 10% detachment, whereas SJS is widespread purpuric macules or flat atypical targets

Distribution

Acral and symmetrical - backs of the hands, forearms, feet, extensor limbs - spreading centripetally, the opposite of the truncal onset of epidermal necrolysis. Major disease means mucosal involvement, most often the lips and mouth.

Photographs

Erythema multiforme involving the mouth: erosions and sloughing membrane over the tongue and buccal mucosa. Mucosal involvement is exactly w — Erythema multiforme involving the mouth: **erosions and sloughing membrane over the tongue and buccal mucosa.** Mucosal involvement is exactly what makes it **major** rather than minor, so this is the finding that changes the disposition. Look in the mouth of every patient with target lesions. The harder judgement is the boundary with Stevens-Johnson syndrome, which turns on whether the skin lesions are **localised typical targets** or **widespread atypical ones** - if there is any doubt, treat it as SJS.
Fitzpatrick I-III (Fitzpatrick type estimated from the photograph, not stated by the source) · Sadandy · Wikimedia Commons - erythema multiforme of the tongue · CC BY-SA 4.0

Provenance for every photograph in this library: image licences. How much of the corpus still has no darker-skin photograph: skin tone coverage.

Mimics

Stevens-Johnson syndrome / toxic epidermal necrolysis — The distinction that matters most on this page. EM major is acral, raised and palpable, usually herpes-driven; SJS/TEN is truncal, flat and dusky, drug-driven, with detachable epidermis - and goes to a burns centre
Pemphigus vulgaris and bullous pemphigoid - the acute presentation — Both erode mucosa; immunobullous disease evolves over weeks and lacks target lesions
Eczema herpeticum — Both herpes-associated, but herpeticum gives disseminated monomorphic punched-out erosions on eczematous skin rather than acral targets

What to do in the ED

Decide explicitly whether this is EM major or epidermal necrolysis, and record the reasoning - distribution, whether lesions are raised, and whether epidermis is detachable
Look for and treat the trigger: ask about cold sores, and consider mycoplasma in a child with respiratory symptoms
Assess oral intake and hydration; mucosal pain is what usually determines admission
Analgesia, mouth care and a topical anaesthetic or barrier as appropriate; ophthalmology the same day for any eye involvement
Refer to dermatology. Admit if oral intake cannot be maintained, if there is extensive mucosal disease, or if the diagnosis is not secure
Warn about recurrence, which is common with herpes-associated disease, and refer for consideration of suppressive antiviral treatment if attacks are frequent

Disposition

URGENT DERM

Urgent dermatology. Admit where mucosal involvement prevents adequate oral intake, where there is ocular involvement, or where epidermal necrolysis has not been confidently excluded - in which case manage as necrolysis until it has.

Safety-netting

If discharged: return if the rash spreads onto the trunk, if the skin becomes painful or starts to peel or blister in sheets, if you cannot drink enough, if the eyes become red or painful, or if you develop a fever. Arrange review within 48 hours.

Local variation

There is no UK national guideline specific to erythema multiforme major; the practical reference point is the UK epidermal necrolysis guidance, which addresses the boundary between the two.

Sources

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