Description
A 25-year-old lady presented with symmetrically distributed acral target lesions. She was otherwise asymptomatic, with no infective contacts, but concerned given the sudden onset and extensive distribution (figure 1). Erythema multiforme (EM) can be an alarming sign for patients and healthcare professionals. The exact pathophysiology of the characteristic lesions is unknown, but it is thought to be immune-mediated, likely to involve a type IV hypersensitivity reaction in response to certain medications or illnesses.1 When examining the patient with EM, one must carefully look for signs of mucosal involvement, as this distinguishes EM minor (target lesions alone) from EM major (additional involvement of one or more mucus membranes).2 The majority of cases of EM minor require no treatment, and concurrent illness is mild and self-limiting. If a drug cause is suspected, the offending agent should be stopped. Treatment directed towards an infective agent can be commenced if this is a suspected trigger (most commonly herpes simplex virus and Mycoplasma pneumoniae). Eye involvement should be assessed/treated by an ophthalmologist. EM major may require hospital admission, particularly if oral involvement limits fluid intake.3 Frequently EM is recurrent, possibly related to a persistent antigenic stimulus. Patients should be warned of this possibility. Failure of EM to resolve, despite suppressive antiviral therapy and stopping of an offending drug will require dermatological referral for further treatment.1 In this patient, there was no mucosal involvement and no further treatment was required: a diagnosis of idiopathic EM was made. The lesions resolved spontaneously over 7–10 days.
Figure 1.
Erythema multiforme (right knee joint).
Learning points.
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Erythema multiforme is an important clinical sign that can represent multiple underlying pathologies.
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Careful history taking can enable identification of a precipitant, however in some cases this will not be possible.
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In the majority of patients, EM is a benign self-limiting disease. Reassurance to patients and their families is often all that is required.
Footnotes
Competing interests None.
Patient consent Obtained.
References
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- 2.Bastuji-Garin S, Rzany B, Stern RS, et al. Clinical classification of cases of toxic epidermal necrolysis, Stevens-Johnson syndrome, and erythema multiforme. Arch Dermatol 1993;129:92–6 [PubMed] [Google Scholar]
- 3.Al-Johani KA, Fedele S, Porter SR. Erythema multiforme and related disorders. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007;103:642–54 [DOI] [PubMed] [Google Scholar]