心筋生検で著明なび漫性心筋線維症を認めた甲状腺機能低下症の1例

A case of myxedema with diffuse myocardial fibrosis proven by endomyocardial biopsy

　症例は66歳の女性。36歳時にバセドウ病の診断のもとに甲状腺亜全摘を受け，40歳時には甲状腺機能低下症と診断された。約1年間は甲状腺ホルモン補充療法を受けたが，その後の経過観察は不十分で服用を中断した期間が長かった。64歳時には呼吸困難を自覚し，心嚢液貯留を指摘された。昭和63年4月頃（66歳）より浮腫と息苦しさが増強するため，同年8月に当科に入院。甲状腺機能検査では，一次性機能低下の所見を呈した。胸部X線では肺うっ血を認め，心胸郭比は69％。心電図は肢誘導低電位と完全左脚ブロック様の心室内伝導障害を呈した。心エコー図では心嚢液貯留を，左室造影では内腔の拡張とび漫性壁運動低下（駆出率27％）を認め，拡張型心筋症に類似していた。右室心内膜心筋生検では，著明なび漫性の線維症を認めた。粘液水腫心の心病変は可逆性と考えられているが，同症であっても不可逆性心筋病変を生じ得ることを示す興味ある1例と考え報告した。

We report a middle-aged woman with myxedema heart who presented both clinical features resem-bling dilated cardiomyopathy and the diffuse myo-cardial fibrosis proven by endomyocardial biopsy. Thirty years previously, when she was 36 years old, partial thyroidectomy had been performed after a diagnosis of hyperthyroidism was made. Four years later, she experienced dry skin and peripheral edema, and hypothyroidism was diag-nosed. Several months after, replacement therapy for hypothyroidism improved her symptoms. How-ever, the therapy was discontinued because of her ignorance of the disease. Twenty six years later (64 years old), she felt exertional dyspnea, and was admitted to Fukuoka University Hospital for evalua-tion of her cardiac state. Thyroid function test re-vealed primary hypothyroidism with low T3, low T4 and high TSH levels. Cardiotharcic ratio on chest X-ray film was 69%. Electrocardiogram showed low voltage in the limb leads and intraventricular con-duction disturbance. Echocardiogram demonstrated marked dilatation and severely reduced wall motion of the left ventricle and pericardial effusion. Left ventriculogram showed diffuse hypokinesis with 27 % of the ejection fraction. No significant stenosis was observed on coronary arteriogram. Seventeen-month replacement therapy did not improve these cardiac findings significantly. Transvenous right ventricular endomyocardial biopsy demonstrated diffuse myocardial fibrosis without inflammatory infiltrate, which was interpreted as a sequel of interstitial lesions of the myxedema heart such as edema or mucoid infiltration. This pathological finding suggests that long-standing untreated hypo-thyroidism can cause irreversible myocardial dam-age.