慢性血栓塞栓性肺高血圧症として長期管理された敗血症性肺塞栓症の1例

A Patient with Septic Pulmonary Embolism Derived from the Tricuspid Valve Endocarditis Mimicking Chronic Thromboembolic Pulmonary Arterial Hypertension

要旨　症例は28歳女性．自己注射による薬物乱用を行っていた．2008年8月から39℃台の発熱が持続し，10月に当院内科外来を受診した．胸部X線にて，両側肺野で末梢側に優位な斑状の浸潤影を認めた．血液培養にてα-streptococcusが検出されたが，心内には疣腫を認めず，肺炎との診断のもと一般的な抗菌薬治療にて肺野陰影は消失した．しかし，労作時息切れと下腿浮腫は残存し，肺動脈の塞栓像と肺高血圧の所見から慢性血栓塞栓性肺高血圧症に伴う右心不全と診断された．利尿薬とワルファリンを投与されても呼吸困難は持続し，2009年7月に当科へ紹介された．高度三尖弁逆流に対し三尖弁置換術を施行し，術中所見から疣腫形成による三尖弁破壊と診断された．右心系感染性心内膜炎およびその併発症である敗血症性肺塞栓症は典型的な所見に乏しく，診断が時に困難である．特徴的な画像所見から本症を疑い，早期より適切な診断と治療を行うことが肝要である．

　A 28-year-old woman, with a past history of drug abuse, had complained of remittent fever for over 2 months. Her chest X-ray showed patchy infiltrates in the bilateral fields, and her echocardiogram documented severe tricuspid regurgitation. The blood bacterial culture was positive for α-streptococci. However, she was not diagnosed as a patient with infective endocarditis because of no positive signs of intracardiac vegetation. Her therapy consisted of conventional antibiotics under a tentative diagnosis of bacterial pneumonia. In spite of complete recovery from pulmonary infiltrates and remittent fever, her exertional dyspnea and leg edema continued. Even diuretics and anticoagulants given to relieve chronic thromboembolic pulmonary hypertension could not improve her symptoms. Finally, to treat her refractory right-side heart failure, a tricuspid valve was operatively removed and replaced with an artificial one. At the time of the operation, a diagnosis of infective endocarditis seemed to be validated due to the lesions of the destroyed tricuspid valve and ruptured chorda tendineae. Using only conventional diagnostic tools, as in this case, right-sided endocarditis is often difficult to differentiate from other diseases such as chronic thromboembolic pulmonary hypertension and the presence of septic pulmonary embolism itself is a strong characteristic of this disease.