Factor II Deficiency

Written by Janet Barwell and Winnie Yu | Published on July 25, 2012
Medically Reviewed by George Krucik, MD


Factor II deficiency is a very rare blood clotting disorder that results in excessive or prolonged bleeding after an injury or surgery. Factor II, also known as prothrombin, is a protein made in your liver that plays an essential role in blood clotting. It is one of about 13 clotting factors involved in the proper formation of blood clots.

What Role Does Factor II Play in Normal Blood Clotting?

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:


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 the blood stream. They tell 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, the fibrin 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 will not be able to form secondary fibrin clots properly. As a result, you may have prolonged and excessive bleeding.

What Causes Factor II Deficiency?

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 is caused by a recessive gene, which means that both parents must carry the gene in order to pass it on. There are only 26 known cases of inherited factor II deficiency in the world. 

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

  • vitamin K deficiency
  • liver disease
  • medications such as anticoagulants, warfarin, or Coumadin
  • production of autoimmune inhibitors that disable healthy clotting factors

What Are the Symptoms of Factor II Deficiency?

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
  • nose bleeds
  • bleeding gums
  • heavy or prolonged menstrual periods
  • internal bleeding in your organs, muscles, skull, or brain (relatively rare)

How Is Factor II Deficiency Diagnosed?

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

How Is Factor II Deficiency Treated?

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 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 cannot 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 are planning any surgeries or invasive procedures, infusions of clotting factor or other treatments may be required to minimize bleeding risks.

What Is the Long-Term Outlook for Factor II Deficiency?

With proper control, you can lead a normal and healthy life with mild to moderate factor II deficiency. If your deficiency is severe, you will need to work closely with a hematologist throughout your life to reduce bleeding risks and control bleeding episodes.

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