Four cases of oral erythema multiforme

Erythema multiforme (EM) is an immune-mediated disorder of the skin and mucous membranes caused by infections and drugs.The mucosal manifestations are erythema and erosions of the skin and mucous membranes.In the classification used in Japan, EM is classified as EM major (EMM) and EM minor (EMm) , depending on the presence or absence of mucosal manifestation.There exists a type of EM that is localized to the oral cavity without accompanying skin symptoms (oral EM) , which is recognized and classified as EMm overseas.However, in Japan, it does not fall under either EMM or EMm, and there have been few case reports of this condition.Herein we report four cases of oral EM.Of the four cases, two were drug-induced EM and two were herpes simplex virus (HSV) -induced EM.Patients 1 and 2 had cases of drug-induced oral EM; acetaminophen and Asgen were identified as the causative drugs due to positive drug lymphocyte stimulation tests.Patients 3 and 4 had a history of herpes infection prior to the onset of oral ulcers, and experienced recurrent oral ulceration after HSV infection.Therefore, we diagnosed them with HSV-induced oral EM based on these typical clinical features.Oral EM is associated with poor oral intake due to mucosal involvement and could develop into EMM.It is important to diagnose early and prevent recurrence and worsening of EM.Oral EM is not well-known in Japan and it is necessary to reconsider the classification of EM in Japan.