Factor V deficiency is also known as Owren’s disease or parahemophilia. It’s a very rare blood clotting disorder that results in slow or prolonged blood clotting after an injury or surgery.
Factor V, or proaccelerin, is a protein made in your liver that helps convert prothrombin into thrombin. This is an important step in the blood clotting process. Your blood clots may be too weak to stop you from bleeding if you don’t have enough factor V or if it doesn’t work properly.
Factor V deficiency may occur at the same time as factor VIII deficiency, producing more severe blood clotting problems. A combination of factor V and factor VIII deficiencies is considered to be a separate disorder.
Normal clotting process
Factor V is one of about 13 clotting factors responsible for normal blood coagulation. Blood clotting occurs in stages:
- When one of your blood vessels is cut, it immediately constricts to slow blood loss. This is called vasoconstriction. It then releases cells into your bloodstream that tell the blood clotting factors to start the coagulation process.
- Blood platelets collect at the site of the wound and begin sticking to the wound and to each other. This forms a soft platelet plug in your wound. This stage is called primary hemostasis.
- Once the platelets form a temporary plug, a complex chain reaction takes place among multiple blood clotting factors. Factor V appears about halfway through this chain of reactions and converts prothrombin into thrombin.
- Thrombin triggers fibrinogen to produce fibrin, which is the material that makes up the final blood clot. Fibrin is a stringy protein that wraps itself in and around the temporary soft clot, which makes the clot harder. This new clot seals the broken blood vessel and creates a protective covering for tissue regeneration. This stage is called secondary hemostasis.
- After a few days, the fibrin clot starts to shrink, pulling the edges of the wound together to allow the damaged tissue to rebuild. As the underlying tissue is rebuilt, the fibrin clot dissolves.
Secondary hemostasis doesn’t occur properly if you have factor V deficiency. This results in prolonged bleeding.
Factor V deficiency may be inherited or acquired after birth.
Hereditary factor V deficiency is extremely rare. It’s caused by a recessive gene, which means that you have to inherit the gene from both of your parents in order to show symptoms. There are only 105 documented cases of inherited factor V deficiency in the world.
Acquired factor V deficiency may be caused by certain medications, underlying medical conditions, or an autoimmune reaction.
Conditions that might affect factor V include:
- disseminated intravascular coagulation, which is a condition that causes small blood clots and excessive bleeding due to overactive clotting proteins
- liver diseases, such as cirrhosis
- secondary fibrinolysis, which occurs when fibrin clots tend to break down
- autoimmune diseases, such as lupus
- spontaneous autoimmune reactions after surgery or childbirth
- certain types of cancer
The symptoms of factor V deficiency are generally very mild. Factor V levels can be as low as 10 to 20 percent of normal and your blood will still clot, although a bit more slowly.
In cases of severe factor V deficiency, the symptoms may include:
Many people who have this condition received their diagnosis when doctors ran blood coagulation tests before surgery. Common lab tests for factor V include the following:
- Factor assays measure the performance of specific clotting factors to identify missing or poorly performing factors.
- Factor V assay measures how much factor V you have and how well it works.
- Prothrombin time measures clotting time affected by factors I, II, V, VII, and X.
- Partial prothrombin time measures clotting time affected by factors VIII, IX, XI, XII, and von Willebrand factors.
- Inhibitor tests determine if your immune system is suppressing your blood clotting factors.
- Your doctor will likely order other tests to identify any underlying conditions resulting in factor V deficiency.
Factor V deficiency is treated with infusions of fresh frozen plasma (FFP) and blood platelets. These infusions are typically needed only after surgery or a bleeding episode.
As a precautionary measure, your doctor may recommend you use desmopressin (DDAVP) before surgery or dental procedures. DDAVP is a nasal spray that temporarily boosts your factor levels.
Factor V deficiency is relatively manageable compared to other blood clotting disorders. Most people who have this condition need treatment only after surgery or a very serious injury. These people usually have normal lives and only bleed a little bit longer than people who have blood that coagulates normally.