肥大型心筋症様病態と心囊液貯留を来したミトコンドリア心筋症の１例

A Case of Mitochondrial Cardiomyopathy with Pericardial Effusion

要旨

　従来，外眼筋麻痺を主体とするミトコンドリア脳筋症(慢性進行性外眼筋麻痺：chronic progressive external ophtalmoplegia；CPEO)では，そのうちのKearns-Sayre症候群にて房室ブロックはみられるが，肥大型あるいは拡張型心筋症様の心筋障害は少ないとされてきた．しかし，われわれは，従来の報告にない稀な1例を経験したので報告する．症例は72歳，男性．全身の筋力低下，両眼瞼下垂あり，慢性進行性外眼筋麻痺と診断されていたが，9カ月後，歩行時の息切れ，心胸郭比の増大を来し入院した．心エコー検査で，左室心筋の全周性の肥厚と輝度の増強を認め，壁運動が低下していた．右室壁も肥厚し，中等量の心嚢液を認めた．胸部写真にて肺うっ血はなく，利尿剤の投与にて心嚢液は消失した．血液生化学的検査ではCRP陰性，甲状腺機能正常であり，¹²³I-BMIPP心筋シンチではびまん性に取り込みが低下していた．心臓カテーテル検査では肺動脈圧62/25mmHg，右室および左室拡張末期圧は15mmHg，24mmHgと上昇し，左室駆出率は45％と低下していた．両心室の心筋生検では両心室に同程度のミトコンドリア病病変が認められた．これまでのCPEOの心病変の報告と異なり，著明な心肥大から収縮不全と拡張不全を来し，心嚢液貯留を伴った極めて稀なCPEOと診断された．本症の管理には収縮不全に対してのみならず，拡張不全にも十分な配慮が必要と思われる．

Summary

　Hitherto, Kearns-Sayre syndrome（the clinical triad; progressive external ophthalmoplegia, pigmental retinopathy, and atrio-ventricular block）has been reported usually showing cardiac involvement such as AV block. In the milder form,CPEO（chronic progressive external ophthalmoplegia）produced by a mitochondrial disorder has been reported to be a rare cardiac involvement in contrast to MELAS（mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes）or MERRF（myoclonus epilepsy associated with ragged-red fibers). Thus, we present in this report a rare case of CPEO associated with cardiac hypertrophy accompanied with systolic and diastolic dysfunction and pericardial effusion. A 72-year-old man was admitted to the hospital complaining of shortness of breath. Nine months before admission, he was diagnosed as having chronic progressive external ophthalmoplegia induced by a mitochondrial disorder. The chest X-ray film, which was made on admission, showed cardiac enlargement without pleural effusion. Echocardiography revealed moderate pericardial effusion, diffuse hypertrophy of both ventricles, and hypokinesis of the inferior wall of the left ventricle. E/A ratio obtained by means of a pulsed Doppler examination suggested decreased diastolic function of both ventricles even after disappearance of the pericardial effusion. ¹²³I-BMIPP myocardial SPECT showed patchy hypo-perfusion of the left ventricle. Coronary angiography demonstrated no narrowing of the large arterial vessels. The hemodynamic study revealed pulmonary hypertension(62/25mmHg）and elevation of right and left ventricular end-diastolic pressure(15mmHg and 24mmHg). The ejection fraction of the left ventricle was 45%. Frozen specimens of left and right ventricles stained by Gomori-trichrome, showed a reddish purple deposit indicating an increase of abnormal mitochondria. Moreover, the activity of cytochrome C oxidase had decreased. This CPEO case is considered to be very rare, showing diastolic and systolic dysfunction in both ventricules accompanied with pericardial effusion.