A fairly common and often benign valvular heart disorder characterized by redundancy or hooding of mitral valve leaflets so that they prolapse into the left atrium, often causing mitral regurgitation. It is often a symptomless condition but may be marked by varied symptoms (e.g. chest pain, fatigue, dizziness, dyspnea, or palpitations) leading in some cases to endocarditis or ventricular tachycardia.