It is the only cardiac valvular disease that is predominantly rheumatic in origin and acounts for about 50 percent of all rheumatic valve disease.
MSは、ほとんどがリウマチ性に生じる唯一の心臓弁膜症であり、全リウマチ性弁膜症の約50％を占める。
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predominantly http://eow.alc.co.jp/predominantly/UTF-8/