马凡综合征二尖瓣，见小叶增大, 在左方远处的一个小叶向上隆起。这是二尖瓣脱垂的特点。固定小叶的腱索变得细长。体格检查时发现的收缩中期期卡嗒音为其特征表现。
The mitral valve is shown in the same patient with Marfan's syndrome. The leaftlets of the mitral valve are redundant, and the one on the far left is ballooned upward. This is characteristic of floppy mitral valve with mitral valve prolapse. The chordae tendineae that hold the leaflets become long and thin. The characteristic finding on physical exam is a mid-systolic click.