An anatomical defect of the Mitral valve, causing prolapse of one of the valvular leaflets towards the atrium during closure.

It is a frequent disorder, with increased frequency of appearance in women at age 20 to 40, with a hereditary component.

Most often, the structural defect is unnoticed and is detected incidentally, but sometimes it can cause leakage during valvular closure (Mitral regurgitation).