Your 16 yo cousin comes to you with a one-week history of sore throat, difficulty swallowing and painful lesions of his lips, oral mucosa and oropharynx. He also has what he calls “blisters” on his hands. What does he have?
Erythema Multiforme (EM) is an immune-mediated, self-limiting condition. The trigger is, 90% of the time, infection, the most common of which herpes simplex. Other triggers include, medications, malignancy, autoimmune disease, immunizations, radiation, sarcoidosis, and menstruation.
Sometimes only the typical targetoid skin lesions occur. These consist of a central small, dark, crusty area or blister surrounded by concentric rings of pallor and erythema. Lesions may affect mucosal surfaces, which is called EM major. Ulcers are widespread, involve many oral surfaces but (this is important) virtually always involve the lips in the form extensive crusting, bleeding and oozing. The hard palate and gingiva are usually spared. In the past, EM used to encompass Stevens Johnson Syndrome (SJS) but new studies show that they are histopathologically distinct entities and should not be treated the same way.
Treatment with oral antivirals after the appearance of HSV-associated EM does not affect the clinical course of the eruption. HSV associated EM usually appears ~8days after the HSV eruption. Severe cases, where mucosal lesion involvement affects patient daily function (eating, vision, toileting etc) specialist referral is indicated, and short courses of PO or topical steroids are recommended.
Another disease with oral ulceration and skin lesions is hand-foot-and-mouth. HF&M usually affects younger children (usually age 5 to 10) and oral lesions are much more limited and in the form of discrete vesicles located further back in the mouth.
Could your cousin be presenting with primary herpes? A good thought. But not typically with targetoid cutaneous lesions…
EM is self-limited; it should resolve within 1 to 3 weeks. It may recur, but there should be a period of resolution, or else there may be some other etiology for the eruption.
Assier H, Bastuji-Garin S, Revuz J, Roujeau JC. Erythema multiforme with mucous membrane involvement and Stevens-Johnson syndrome are clinically different disorders with distinct causes. Arch Dermatol 1995; 131:539.
Wetter DA, Davis MD. Recurrent erythema multiforme: clinical characteristics, etiologic associations, and treatment in a series of 48 patients at Mayo Clinic, 2000 to 2007. J Am Acad Dermatol 2010; 62:45.
Images from Rosh Review and Oral Path