Erythema Multiforme
Abstract & Commentary
By John Shufeldt, MD, JD, MBA, FACEP, Chief Executive Officer, NextCare, Inc.; Attending Physician/Vice Chair, Department of Emergency Medicine, St. Joseph's Hospital and Medical Center, Mesa, AZ, is Editor for Urgent Care Alert.
Synopsis: Overview of the diagnosis and treatment of erythema multiforme
Source: Lamoreux MR, et al. Erythema multiforme. Am Fam Physician. 2006;74:1883-1888.
Erythema Multiforme (EM) is a self-limited hypersensitivity reaction which is often recurring. It is associated with both infectious processes and certain medications. The common infections associated with EM are Herpes Simplex virus 1 and 2 (HSV), Mycoplasma pneumonia, and fungal infections. Common medications that can cause EM are barbiturates, hydantoins, NSAIDs, penicillins, phenothiazines, and sulfanomides. EM was previously thought to be part of a spectrum of diseases which included erythema multiforme minor, Stevens-Johnson syndrome (SJS), and toxic epidermal necrolysis (TEN). EM is now thought to be a distinct condition since it is characterized by minimal mucosal involvement and infrequent epidermal detachment.
EM often occurs in adults between the ages of 20-40 years old. The most common cause is HSV, which accounts for more than 50% of the cases, followed by mycoplasma and fungal infections. There have also been reports of EM caused by vaccines (DT, Hep-B, and small pox). Other medications (Cipro, Wellbutrin, and Glucophage) and other viruses (varicella zoster, Hep-C, CMV, and HIV) have also been linked to EM.
HSV is often the culprit in recurrent EM. Of note, most patients with HSV infection do not develop EM, and patients with EM caused by HSV often do not have a clinically apparent outbreak of HSV.
The rash associated with EM usually appears distally and spreads proximately. The patient may experience cutaneous purities prior to the rash appearing. The rash begins as sharply demarcated macules that become papular. The characteristic target lesion has a smooth edge with distinct zones. An outer peripheral ring, a lighter inner zone, which may appear pale or pink, and a dark reddish center. These characteristic lesions may not appear for several days when lesions of different morphology are present, hence the name multiforme.
EM is usually a clinical diagnosis. Skin biopsy in not indicated when the lesions are consistent with their typical morphologic pattern and/or when the patient has a coexisting HSV infection. In cases where the rash is not typical or where it is recurrent and without a documented HSV infection, biopsy by a dermatologist may be indicated. The differential diagnosis for EM includes urticaria, viral exanthems, vasculitis, pityriasis rosea, lupus erythematosus, drug reason, and other hypersensitivity reactions.
Typical cases of EM do not require treatment other than symptomatic relief with oral antihistamines and topical steroids. In patients with a coexisting HSV infection, treatment with oral acyclovir, valacyclovir, or famciclovir is indicated and will decrease the number of lesions and the duration of the disease. Oral prednisone has also been used; however, it may lower the patient's resistance if they have a coexisting HSV infection. Recurrent EM may be treated with one of the aforementioned antiviral agents, even when HSV in not an obvious precipitating factor. In those patients who have recurrent EM despite aggressive therapy, dermatological consultation is warranted.
Commentary
EM is a frequent diagnosis in the urgent care setting. Often, the offending medication or pathogen is not easily identified. In these patients, the standard of care is to document that no clear pathogen is identified, to identify and refer those patients who are at risk for SJS and TEN, and to treat the patient symptomatically. In patients with a coexisting HSV infection, the use of an oral antiviral medication is indicated. I would not place the patient on oral steroids since there has never been a controlled study which has shown that oral steroids are effective in ameliorating the rash of EM.
Erythema Multiforme (EM) is a self-limited hypersensitivity reaction which is often recurring. It is associated with both infectious processes and certain medications.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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