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Factor II deficiency is a very rare blood clotting disorder. It results in excessive or prolonged bleeding after an injury or surgery.

Factor II, also known as prothrombin, is a protein made in your liver. It plays an essential role in blood clot formation. It’s one of about 13 clotting factors involved in the proper formation of blood clots.

Symptoms may vary from mild to severe. In very mild cases, blood clotting may just be slower than normal.

In cases of severe factor II deficiency, symptoms may include:

  • umbilical cord bleeding at birth
  • unexplained bruising
  • abnormal bleeding after giving birth, having surgery, or being injured
  • prolonged nose bleeds
  • bleeding from the gums
  • heavy or prolonged menstrual periods
  • internal bleeding in your organs, muscles, skull, or brain (relatively rare)

To understand factor II deficiency, it helps to understand the role of factor II (prothrombin) and its activated version, factor IIa (thrombin), in normal blood clotting. Normal blood clotting occurs in four stages, described below.


When you have a wound or surgery, your blood vessels are broken.The broken blood vessels immediately constrict to slow blood loss.

The damaged vessels then release special cells into your bloodstream. They signal the blood platelets and clotting factors circulating in your bloodstream to come to the wound site.

Formation of a platelet plug

Blood platelets (specialized blood cells responsible for clotting) are the first responders to the site of a damaged blood vessel.

They attach themselves to the injured blood vessel and to each other, creating a temporary patch over the injury. This first stage of blood clotting is known as primary hemostasis.

Formation of a fibrin plug

Once the platelets form a temporary plug, blood-clotting factor II (prothrombin) changes to its activated version, factor IIa (thrombin). Factor IIa causes factor I (fibrinogen) to make the stringy protein fibrin.

Fibrin wraps itself in and around the temporary clot until it becomes a hard fibrin clot. This new clot seals the broken blood vessel and creates a protective covering over the wound. This is called secondary hemostasis.

Wound healing and dissolution of the fibrin plug

After a few days, thefibrin clot starts to shrink, pulling the edges of the wound together to promote new tissue growth. As the new tissue closes the wound, the fibrin clot dissolves.

If you don’t have enough factor II, your body won’t be able to form secondary fibrin clots properly. As a result, you may have prolonged and excessive bleeding.

Factor II deficiency may be inherited. It can also be acquired as a result of disease, medications, or an autoimmune response.

Hereditary factor II deficiency is extremely rare. It’s caused by a recessive gene, which means that both parents must carry the gene in order to pass the disease on. There are currently only 26 documented cases of inherited factor II deficiency in the world.

Acquired factor II deficiency is usually caused by an underlying condition, such as:

Diagnosis of factor II deficiency is based on your medical history, any family history of bleeding problems, and lab tests. Lab tests for bleeding disorders include:

  • Factor assays: These tests check the performance of specific factors to identify missing or poorly performing factors.
  • Factor II assays: These measure the levels of factor II in your blood.
  • Prothrombin time (PT): PT measures the levels of factors I, II, V, VII, and X based on how quickly your blood clots.
  • Partial prothrombin time (PTT): Like PT, this measures levels of factors VIII, IX, XI, XII, and von Willebrand factors based on how quickly your blood clots.
  • Other tests: These may be done to test for underlying conditions that may be causing your bleeding problems.

Treatment of factor II deficiency focuses on controlling bleeds, treating underlying conditions, and taking preventive steps before surgeries or invasive dental procedures.

Controlling bleeding

Treatment for bleeding episodes may include infusions of prothrombin complex, a mixture of factor II (prothrombin) and other clotting factors, to boost your clotting ability.

Infusions of fresh frozen plasma (FFP) have been used in the past. They are less common today, thanks to lower-risk alternatives.

Treatment of underlying conditions

Once your bleeding is under control, underlying conditions that impair blood platelet function can be treated.

If your underlying condition can’t be resolved, the focus of your treatment will shift to managing the symptoms and impacts of your clotting disorder.

Prophylactic treatment before surgery

If you’re planning any surgeries or invasive procedures, infusions of clotting factor or other treatments may be required to minimize bleeding risks.

With proper control, you can lead a normal and healthy life with mild to moderate factor II deficiency.

If your deficiency is severe, you’ll need to work closely with a hematologist (a doctor who specializes in blood disorders) throughout your life to reduce bleeding risks and control bleeding episodes.

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