上嶋 亮¹, 鈴木 健吾¹, 出雲 昌樹¹, 黄 世捷¹, 水越 慶¹, 高井 学¹, 立石 文子², 明石 嘉浩¹, 信岡 祐彦³, 三宅 良彦¹

Ryo KAMIJIMA¹, Kengo SUZUKI¹, Masaki IZUMO¹, Seisyou KOU¹, Kei MIZUKOSHI¹, Manabu TAKAI¹, Ayako TATEISHI², Yoshihiro J. AKASHI¹, Sachihiko NOBUOKA³, Fumihiko MIYAKE¹

¹聖マリアンナ医科大学循環器内科, ²聖マリアンナ医科大学診断病理学, ³聖マリアンナ医科大学臨床検査医学

¹Division of Cardiology, Department of Internal of Medicine, St. Marianna University School of Medicine, ²Department of Diagnostic Pathology, St. Marianna University School of Medicine, ³Departrnent of Laboratory Medicine, St. Marianna University School of Medicine

キーワード : nonbacterial thrombotic endocarditis, NBTE, transesophageal echocardiography

症例は50歳，女性．34歳時に全身性エリテマトーデスと診断され，ステロイド内服加療を受けていた．スクリーニング目的で施行した経胸壁心エコーで左室流出路に突出した僧帽弁前尖の腫瘤性病変を認めた．その後施行した3D経食道心エコーでも，左室流出路の約2/3程度を占める腫瘤が確認され，さらに左房側にも同様の小腫瘤の付着を認めた．ステロイド服用に伴う易感染状態であったが，感染兆候を示す所見はなく，複数回採取した血液培養も全て陰性．Duke診断基準を満たさず，感染性心内膜炎は否定的であった．形状や付着部位，SLEの臨床背景より非細菌性血栓性心内膜炎（nonbacterial thrombotic endocarditis: NBTE）が疑われた．頭部CTにて散在する陳旧性脳梗塞像を認め，その付着部位や可動性から重症塞栓の高リスクと判断し，準緊急的に腫瘤摘出術，僧帽弁置換術を施行した．腫瘍は肉眼的に多房性，軟であり，組織学的には好中球と組織球浸潤を伴うフィブリン血栓を認め，NBTEと診断した．術後経過良好で，新規塞栓症状の出現はなく術後第19病日に退院となった．NBTEは悪性腫瘍などに伴う過凝固状態や免疫複合体などによる内皮細胞損傷を背景に発症することが多いとされる．本症例は経食道心エコーを用いることでその局在や形状，付着部位を詳細評価し神経学的後遺症を残さず治療し得た1例であり，考察を加えて報告する．

The patient was a 50-year-old female. She had received treatment for systemic lupus erythematosus (SLE) with glucocorticoid since she was 34 years old. Transthoracic echocardiography performed for screening showed a mass adjacent to the anterior leaflet of the mitral valve and protruding into the left ventricular outflow tract. Follow-up 3D transesophageal echocardiography depicted the mass, which occupied approximately two-thirds of the left ventricular outflow tract, and another small mass toward the left atrium. She had an opportunistic infection caused by glucocorticoid therapy; however, the blood cultures ordered several times were all negative. Infectious endocarditis was ruled out because the patient did not meet the Duke diagnostic criteria. The patient was suspected of having nonbacterial thrombotic endocarditis (NBTE) based on the formation of the masses, the diseased area, and her medical history of SLE. Head computed tomograms revealed an old cerebral infarction, suggesting that she should have a high risk of severe embolus determined by the scattered lesion pattern and thrombus mobility. The patient underwent sub-emergency mass removal and mitral valve replacement. The soft and multilocular masses and fibrin thrombus with mixed infiltrate (neutrophils and histiocytes) revealed that the patient had NBTE. The postoperative course was uneventful and no more embolic symptoms were found. She was discharged on the 19th postoperative day. NBTE frequently occurs when endothelial cells are damaged by the immune complexes and hypercoagulability due to malignant tumors. Here, we report the successful evaluation of NBTE using transesophageal echocardiography and the favorable prognosis without any neurological impairment.