What is Factor V Leiden?

Mary McMahon
Mary McMahon

Factor V Leiden is a genetic trait known to predispose people to the formation of blood clots. People with this trait have a variant of Factor V, a protein found in blood and involved in clotting mechanisms, that resists activated protein C, causing clots to develop even after the body releases enzymes to halt the clotting mechanism. This trait can be identified in people during routine screening conducted as part of a diagnostic process, or when they specifically request testing due to concerns about a family history of this genetic variation.

For people with Factor V Leiden, the development of blood clots is a potential risk.
For people with Factor V Leiden, the development of blood clots is a potential risk.

People of European ancestry are more likely to have the Leiden variation of Factor V, first identified in the Netherlands in the 1990s. It is estimated that around three to eight percent of people with European ancestry have at least one copy of the defective gene. Symptoms can vary, depending on the exact variation and how many copies of the gene someone has; for people with Factor V Leiden, the development of blood clots and complications like pulmonary emboli, where a clot enters the respiratory tract, is a potential risk.

Factor V Leiden is diagnosed through a blood test.
Factor V Leiden is diagnosed through a blood test.

Known as a hypercoagulability disorder because it increases the coagulation of the blood, Factor V Leiden is identified by performing a screening test on a patient's blood to see how resistant it is to protein C. In most cases, when this screening shows that the blood is resistant to activated protein C, it means the patient has Factor V Leiden. Combined with a family history of the gene, as well as blood clots in the patient's personal medical history, this can be a strong diagnostic indicator.

Some patients live with this genetic variation their whole lives without being aware of it, either because they are carrying a relatively mild mutation of the gene, or as a result of simply being lucky when it comes to the formation of blood clots. Other individuals may develop symptoms like thrombosis at various points in their lives, usually in response to known risks like flying and certain medications.

People concerned about hereditary blood disorders can opt to undergo genetic testing to screen for common genetic variations. The testing should be supervised by a genetic counselor who can also provide advice and assistance when the test results come back. People with Factor V Leiden can generally live healthy lives, have children, and engage in normal activities, but they do need to be more alert to clotting issues and the early warning signs of thrombosis, and they may be advised to avoid certain risks or to take extra precautions.

Factor V Leiden is hereditary, meaning that it runs in families.
Factor V Leiden is hereditary, meaning that it runs in families.
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

You might also Like

Readers Also Love

Discussion Comments


I have Factor V Leiden and endometriosis and things keep getting worse and worse by the month. I cannot function, am not able to perform simple daily tasks and necessities and I am unable to hold a job or work for long periods of time. I have up to three menstrual cycles a month, and my hormones make me seem constantly bipolar to others.

I do not have a job and my fiance of five years works very hard to make ends meet, but neither of us can afford medical insurance. Would I qualify for medi-cal? Every time I go anywhere to get help, my partner and I are met with lack of understanding of factor V Leiden and/or it is simply not even know about by the doctors we have seen. Basically we wait for something bad to happen then end up in the ER. One time we spoke about it to inform a little about what it is. We were met with snotty comments like, “Haha, did you look that up on the internet?”, “We will tell you what’s wrong. We’re the professionals” “Ma’am, are you a doctor? Well I am, so let me decide what’s going on here”, “Sir, the internet is not a degree” when we are just simply trying to inform them of my diagnosis. Then, when the paper work finally gets sent over, the doctors say “Ooh I’m sorry. I will be back after I do some research about this disorder.” Then they tell us we need to see a specialist, and bam! They discharge me and I’m back home in pain, the problems multiply and we’re back home waiting until something else happens to go back to the ER and it starts all over again.

I have cervical cysts, contortions around them, kidney and liver problems and the last time we went to the ER because one of the cysts was rupturing, they prepped me for surgery the last time. Then, after taking me off of fluids for 24 hours, the doctor came in and said, “What’s going on? I didn’t order any of this. Why is she off of fluids?” I was dehydrated and my organs had started shutting down, and I also had an infection in my kidneys.

I checked myself out after that because first, they prepped me for a surgery that was not ordered and second, they kept giving me the wrong meds -- meds that were not indicated for my conditions. The head nurse helped us fill out incident reports of malpractice and my partner asked the doctor if he even knew what factor V was. He said he didn’t really know a lot about it.

I was also told by three doctors recently that I have endometriosis and the treatments suggested would mess with my factor V leiden disorder, or increase my chances of getting pregnant more which puts me at risk of my factor v leiden disorder and blood clots. My mini strokes were confused with seizures years ago in 2001, and they took my drivers license away without diagnosing me with a seizure disorder. I fought this for years to try and get my drivers license back, but by law, the only way they can take it away is if I have a seizure disorder. Yet it was proved later via EEG that I did not have a seizure disorder and I was never diagnosed with one. They put me on seizure medication because they thought that’s what it was at first, and that ended up causing my kidneys to fail and then I got pregnant and because of the medication my baby ended up with spina bifida. I ended up miscarrying in the 22nd week and while I was pregnant I got a DVT in my left leg.

The seizure meds started actually giving me seizures, they took me off of it and they stopped. Years later, we read how factor V leiden can cause mini strokes that appear to be seizures. I finally got my license back and we ordered copies of my medical records and found out that I never was officially diagnosed with a seizure disorder so they concluded I could drive again. It was after the 2001 incidents that they finally ran the test and I was diagnosed with factor V leiden. Now with endometriosis, everything we read about it does not go well with factor V leaden problems. They want to do surgery that we cannot afford and the risks of me getting blood clots and clotting from surgery are high.

I simply just do not know what to do and this lifestyle is destroying me and my life with my partner. We can’t even sleep because of the pain I am in nightly, and he worries so much that it is affecting his work. He is about to sign a contract for a project and he would be legally obligated to produce what is required.

We have decided that we need to go see if I can get medi-cal so I can maybe get some treatment before this job starts so there is less chance of having something happen that will affect his ability to work at his best. We need the money but are worried that something will mess up the project because of the worsening of my conditions. Times are very stressful, and he is falling apart.

We need help. Are there things we can bring into the social services office when we see a worker that will help us qualify for the benefits?

Post your comments
Forgot password?