By Gary M. White, MD
True target lesions.
Erythema multiforme (EM) is an allergic reaction pattern in the skin that is characterized by multiple target lesion (concentric rings of different shades of red). The center may be dusky, necrotic, or bullous.
Multiple target lesion (concentric rings of different shades of red) are seen most commonly on the hands, but may occur anywhere. Many morphologies may occur e.g., morbilliform, red edematous plaques, bullous lesions, and lesions in a photo distribution. When EM is recurrent, inquire about herpes simplex virus infection as a trigger. Very rarely, EM lesions may be persistent.
Mucosal lesions of the conjunctiva and mouth may indicate Stevens Johnson syndrome. Rarely, the esophagus may be involved. One patient vomited 20 cm of esophageal mucosa. PCR has shown HSV DNA in cutaneous lesions of EM. Sometimes, lesions of EM may encircle melanocytic nevi.
“Herpes Iris of Bateman” is a distinctive skin lesion noted in certain patients of erythema multiforme major that is characterized by a central bulla over an erythematous background and a ring of vesicles at the margin. Indian Dermatol Online J. 2014 Dec; 5(Suppl 2): S138–S139
One of the problems with erythema multiforme is criteria for diagnosis. For some, the diagnosis is not erythema multiforme unless the patient shows true classic target lesions (at least two concentric rings of different shades of red)--as opposed to "atypical" targets. This is more than an academic consideration however, as Herpes infection is much more likely to be associated with EM with true targets.
When there is significant mucosal involvement, see Stevens-Johnson Syndrome. If there is widespread erosive and/or bullous lesions, consider toxic epidermal necrolysis.
If the patient also has lupus, consider Rowell syndrome.
If a likely cause is found, treat it or eliminate it. Prednisone 1 mg/kg initially and tapered over 2 weeks is usually given. See also recurrent EM and persistent for additional treatment options.
EM from minocycline.
Bullous EM. Photograph courtesy Michael O. Murphy, MD
Four pictures of the same patient with bullous EM.
Erythema multiforme precipitated by seal pox.
Erythema multiforme after H1N1 vaccination.
The patient had a herpes breakout of the buttocks accompanied by an EM-like rash localized to the same area. Courtesy Michael O. Murphy, MD
“Herpes Iris of Bateman”: a central bulla over an erythematous background and a ring of vesicles at the margin. Indian Dermatol Online J. 2014 Dec; 5(Suppl 2): S138–S139
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