Erythema multiforme (EM) is a mucocutaneous syndrome characterised by target lesions with or without central blisters, predominantly seen on the face and extremities (see photos). The diversity in clinical pattern implied by the name multiforme is mainly due to findings in each single lesion; most lesions are usually rather similar in a given patient at a given time. Koebner phenomenon is common and photo-aggravation can occur.
EM is usually called minor when mucous membranes are minimally affected (commonly the oral cavity) or spared and is called major when at least two mucosal sites are involved. Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) usually represent adverse reactions to medications. It is considered that EM minor and major are part of one spectrum, often related to infections (especially HSV in recurrent cases) and perhaps on occasion to drug reactions while SJS and TEN are separable from erythema multiforme and are more closely linked to drug sensitivities, and may be regarded as severe variants of a single disease.
EM has a benign course but with frequent recurrences that can be prevented by long-term use of oral anti-HSV drugs. For unresponsive cases, the dose can be doubled or the therapy switched to an alternative anti-HSV drug. It is of interest that patients who suffer from recurrent EM without overt HSV infection might also be helped by prophylactic aciclovir, implying that recurrent HSV infection may nevertheless be responsible without being clinically manifested. EM is usually a disease of young adults with a slight male preponderance occurring seasonally in the spring and autumn. Each self-limited episode lasts 1–4 weeks. Not all episodes of EM are preceded by clinically evident HSV infection, and not all HSV episodes are followed by EM. Thalidomide is probably the most effective treatment of cases resistant to anti-HSV drugs. Aciclovir has been reported to prevent recurrent polyarthritis associated with EM.
This patient has been prescribed continuous oral aciclovir for 6 months at a dose of 400 mg twice daily to prevent recurrence. It should be noted that intermittent treatment with oral aciclovir or the use of topical aciclovir is of little benefit in preventing recurrence. A sunscreen lotion and sunscreen-containing lip balm can be used daily on the face and lips to prevent ultraviolet (UV) B-induced outbreaks of HSV.
This page was last updated in April 2015.