Many posts seem unsure as to exactly what factor V leiden is.
Frequently, no symptoms will show until the mid 20's or 30's - if they do at all. It has the potential to cause complications in pregnancy and may lead to shorten life spans because of an increased chances of heart-attacks and stroke. The chances of heart-attacks are greatly increased if factor II abnormalities are also present. Correcting the mutation would require genetic resequencing - short of Star Trek, that technology is not generally available. Watch your triglycerides and cholesterol, too.