Epstein-Barr virus (EBV) -positive mucocutaneous ulcer (EBVMCU) was first described as a lymphoproliferative disorder in 2010. It is recognized as a mature B-cell tumor in the 2017 WHO classification. EBVMCU results from iatrogenic or age-related immunosuppression and it appears clinically as a localized, well-demarcated ulcerative lesion at the cutaneous or mucosal sites. Histologically, EBV MCUs are characterized by the proliferation of EBV-positive atypical B-cells. In situ hybridization for

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... EBV-encoded small RNA (EBER) reveals many positive cells. Most cases resolve with a reduction in immunosuppression, and some lesions spontaneously resolve. We report a case of EBVMCU that affected the maxillary gingiva. The patient was an 86-year-old woman with an ulcer in the palatal gingiva of the first molar region. At the initial consultation, a biopsy was performed, and we started administration of azithromycin (AZM) at 500 mg/day for 3 days because the left first molar had marginal periodontitis. Immunohistochemistry revealed positive reactions for CD20, CD30, and CD79a, and EBV-encoded small RNA (EBER) was found in many positive cells, which revealed EBVMCU. Because it was considered to have been caused by immune reduction due to aging, follow-up was selected as the treatment strategy. Basic periodontal treatment and oral cleaning instructions were provided in parallel with the follow-up observation. The patient had a spontaneous remission two months after the initial consultation. No recurrence was observed one year after the initial consultation. : Epstein-Barr virus (EBV) -positive mucocutaneous ulcer (EB ウイルス陽性粘膜皮膚潰瘍) , iatrogenic immunosuppression (医原性免疫抑制) , age-related immunosuppression (加齢性免疫低下) , spontaneous remission (自然寛解) 1) 厚生連高岡病院歯科口腔外科 (主任:山下知巳部長) 2) 中濃厚生病院歯科口腔外科 (主任:牧田浩樹部長) 3) 杉田玄白記念公立小浜病院歯科口腔外科 (主任:土井田 誠部長)