Doctors Lounge - Hematology Answers
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Forum Name: Hematology Topics
Question: Factor V Thrombophilia Question
|Neesy - Tue Jul 06, 2010 9:00 pm||
My mother had a pulmonary embolism diagnosed in April following a hysterectomy. Her OBGYN recently ran a blood test which revealed heterozygous factor V Leiden thrombophilia and a few other readings were possibly abnormal, including the lupus reading and It is uncertain right now what else might be going on. She has been referred to a hematologist and is awaiting an appointment.
My sisters and I are all on oral contraceptives. I am 23 and have been taking Ortho Tri Cyclen Lo for 6 years now. I have been doing some reading and many sources online state that heterozygous Factor V Leiden + oral contraceptives can lead to significantly increased risk for developing DVTs.
How likely is it that I also have Factor V Leiden thrombophilia? With the information I have, what should my next step be? Should I wait to refill my Ortho Tri Cyclen Lo prescription based on my possible risk? How quickly should I pursue being tested for Factor V Leiden? Should I make an appointment for myself or should I wait until after my mom's hematologist appointment so that I have more information? If it is advised that I make an appointment soon, should I go straight to a hematologist, an OBGYN, or just my PCP?
Lots of questions, I know!
|Dr.M.Aroon kamath - Tue Aug 03, 2010 7:58 am||
Factor V Leiden (FVL)is an inherited autosomal dominant trait. However, in some cases, factor V Leiden may be inherited as an autosomal recessive trait. This is associated with a greater risk of venous thrombosis.
Each FVL gene is present in pairs, since one is inherited from the mother, and one from the father. Depending on the inheritance of the mutated gene, FVL thrombophilia runs in families in a more severe or a less severe form.
The less severe (but more common) form of autosomal dominant FVL thrombophilia is called "heterozygous" and occurs when an individual inherits only one copy of the altered or mutated gene. If a parent has an autosomal dominant condition, there is a 50% chance for each child to have the same or similar condition.The more severe form of is called "homozygous" and is caused by the inheritance of two mutated copies of the gene.
Autosomal recessive Homozygous FVL thrombophilia is caused by the inheritance of two changed or mutated copies of a gene.This occurs when two people who are heterozygous have children together.Then,there is a 25% chance, with each pregnancy.
Venous thromboembolism (VTE) is a common, very heterogenous disease with variable expressivity as well as genetic and environmental interactions. Heterozygosity for this mutation occurs in at least 3% of unselected, healthy women. FVL is present in heterozygous form in approximately 12–20% of venous thromboembolism (VTE) patients. Its severity and age of onset may vary. Not all mutation carriers develop VTE. The exposure of mutation carriers to other clinical risk factors multiplies the potential risk of VTE.
The lifetime probability of developing thrombosis is considerably less in heterozygotes with the factor V Leiden mutation than in patients with the other less common inherited thrombophilias. Some reports indicate the lifetime probabilities of developing thrombosis are as shown below:
protein S deficiency > antithrombin deficiency > protein C deficiency > factor V Leiden, when compared to controls.
'Combined' thrombophilias [with an additional thrombopilic mutation, for example, activated protein C (APC) resistance] will render an individual more susceptible to thromboembolic events.
Independent risk factors for VTE include older age, confinement to a hospital, recent surgery that required anesthesia, trauma sufficient to necessitate hospitalization,malignant neoplasm (with or without chemotherapy), neurological disease along with chronic extremity paresis, superficial vein thrombosis, and prior central venous catheter or transvenous pacemaker insertion. Additional VTE risk factors for women include the use of oral contraceptives, hormone replacement therapy, and selective estrogen receptor modulators.
Oral contraceptives are contraindicated in women who are homozygotes for factor V Leiden mutation or for women who have previously had thrombosis. However, the majority of carriers are heterozygotes and remain asymptomatic, despite their exposure to transient risk factors for thrombosis. In general, asymptomatic heterozygous carriers of factor V Leiden should be given information on the relative and absolute increased risk of thrombosis, without discouraging the use of second-generation oral contraceptives.
A policy of screening all women before prescription of oral contraceptives, might deny effective contraception to a substantial number of women while preventing only a small number of deaths due to pulmonary emboli. It might be more, practical however, to consider the personal and family history of deep vein thrombosis while deciding to prescribe oral contraceptives.
Thus, testing for factor v leiden mutation is indicated in asymptomatic adult family members of probands with a known factor V Leiden mutation, especially those with a strong family history of VTE at a young age.
You have indicated(in your profile) that your mother underwent a hysterectomy for endometrial hyperplasia (but you have not mentioned the cause for the hyperplasia). This information is important to identify any additional risk for VTE. For example, one of the causes of endometrial hyperplasia is selective estrogen receptor antagonistic therapy(eg; tamoxifen) in breast cancers. Malignancies tend to increase VTE risk.
Whether your mother's VTE episode was primarily due to FVL is hard to say. Were there any other risk factors? Lupus antocoagulant was perhaps positive?- if so, adds to her risk.
Your ( and your sister's) risk of having the FVL mutation is 50% as your mother is heterzygous.Neither you nor your sister presumably had any DVT in the past. At present you do not have any independent risk factors for VTE as well. Also, there is no family history of occurrence of VTE at a young age.It is also good to see that you are well informed about the risk.Therefore, there appears to be no urgency in getting tested for FVL or continuing the oral contraceptives. However, it is better to consult your regular doctor and get tested at the earliest convenience for the inherited thrombophilias.
This will ensure that in future, should an unforeseen event/illness suddenly increases the overall risk, adequate VTE prophylaxis may be instituted without delay.
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