This patient’s targetoid and tingling skin lesions, in association with herpes simplex virus (HSV) infection, are a classic presentation of erythema multiforme (EM).
EM is an acute, self-limited, immune-mediated process that most commonly arises in a symmetrical pattern on acral surfaces. These lesions may be accompanied by eruptions on oral, anogenital, or ocular mucosa. EM is classified into 2 subtypes: major and minor. EM major refers to EM with significant mucosal involvement on at least 2 mucosal sites; it may also manifest with a prodrome of fevers, arthralgias, and malaise. EM minor is used to classify EM with minimal mucosal involvement.1
The term “multiforme” denotes the varied dermatologic changes, including macules, papules, and targetoid lesions with 3 identifiable zones, which are pathognomonic for EM. The classic 3 zones consist of an inner dusky, vesicular, or necrotic center; a middle elevated edematous surrounding ring; and an outer ring of macular erythema. Patients may also present with an atypical macular target lesion, characterized by fewer than 3 zones with an ill-defined border between the zones. The lesions may be asymptomatic, or patients may describe an itchy or burning sensation.
The differential diagnosis of EM includes urticaria, fixed drug eruption, subacute lupus erythematosus, Kawasaki disease, erythema annulare centrifugum, vasculitis, and Stevens-Johnson syndrome.
Infections with HSV types 1 or 2 are the leading cause of EM and are thought to involve a cell-mediated immune process directed against viral antigens in skin.2 Other infectious causes include cytomegalovirus, Epstein-Barr virus, influenza virus, and—rarely—newer strains of coronavirus.3 Pharmacologic reactions are the cause in a small percentage of patients, and may involve nonsteroidal anti-inflammatory drugs, antibiotics, sulfonamides, antiepileptics, and tumor necrosis factor-alpha inhibitors. Studies also link the development of EM to primary malignancy, autoimmune disease, and immunizations.1
The treatment of EM is dependent on the clinical course and severity of the disease. If a causative agent is identified, it should be discontinued (if a drug) or treated (if an infection). Topical antiseptic mouthwashes, antihistamines, and topical corticosteroids can be used to relieve cutaneous discomfort. Biologics and immunosuppressants can be used with patients who have severe symptoms or functional impairment. Patients who have recurrences associated with HSV should be given antiviral prophylaxis for 6 months consisting of oral acyclovir 10 mg/kg/d, valacyclovir 500 to 1000 mg/d, or famciclovir 250 mg twice daily.1
Given the recurrent nature of this patient’s disease, and its association with HSV outbreaks, he was prescribed prophylactic valacyclovir 1000 mg/d orally for 6 months to reduce HSV outbreaks and hopefully prevent future EM episodes.
Photo courtesy of Cyrelle F. Finan, MD. Text courtesy of Lynn Midani, BS, University of New Mexico School of Medicine, and Cyrelle F. Finan, MD, Department of Dermatology, and Daniel Stulberg, MD, FAAFP, Department of Family and Community Medicine, Western Michigan University Homer Stryker, MD School of Medicine, Kalamazoo.