It's fairly common.
Mitral valve prolapse affects around 2 percent of people in the United States [source: Mayo]. Some estimates place the frequency as high as 5 percent [source: Merck]. It occurs as often in men as it does in women.
Knowing that MVP is a common condition may make it easier for the rest of us to swallow the news that we may have it as well. Here's some more reassurance -- MVP may not cause you any trouble whatsoever. The majority of people with MVP lead perfectly healthy, happy lives [source: AHA]. It won't matter if your leaflets are the size of palm leaves, as long as the leaflets still properly function. The main worry is that if the leaflets bulge out, blood will regurgitate into the atrium. This isn't always the case, however. Sometimes prolapsed leaflets still form a tight seal and prevent blood from leaking through.
If there is leakage, it will probably produce a small murmur that your doctor can detect. If there's no sign of regurgitation and no other symptoms, then you may never know there was anything slightly different about your mitral valve in the first place.
If MVP is diagnosed without major symptoms, doctors will keep tabs on the condition throughout your lifetime to make sure your MVP isn't worsening. And here's more good news: A symptom-free condition won't take a single day off your life [source: Mayo].