What Are Rare Bleeding Disorders?

In the US, a rare disease or disorder is defined as one that affects fewer than 200,000 people. This means hemophilia A and B, and the less-common factor deficiencies such as I, II, V, VII, X, XI, XII and XIII, are all rare disorders.

Blood clotting is a complex process, involving many different proteins, called factors, each of which plays a different role in the blood clotting process. Factor deficiencies are defined by which specific clotting protein in the blood protein is low, missing or doesn't work properly.​

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How Many People Have Rare Factor Deficiencies?

Factor I (1) Deficiency
Factor I deficiency is a collective term for three rare inherited fibrinogen deficiencies. One of these, afibrinogenemia is very rare, occurring in 1-2 people per million.

Factor II (2) Deficiency
Factor II deficiency is estimated to occur in 1 out of every 2 million people.

Factor V (5) Deficiency
Factor V deficiency is estimated to occur in 1 out of every 2 million people.

Factor VII (7) Deficiency
Factor VII deficiency is estimated to occur in 1 out of every 300,000-500,000 people. That makes it the most common of the rare factor deficiencies.

Factor X (10) Deficiency
Factor X deficiency is estimated to occur in 1 in 500,000 to 1 in a million people.

Factor XI (11) Deficiency (Hemophilia C)
Factor XI deficiency is estimated to occur in 1 in 100,000 people.

Factor XII (12)
Factor XII deficiency is estimated to occur in 1 in a million people.

Factor XIII (13) Deficiency
Factor XIII deficiency is estimated to occur in 1 in 5 million people. It is the rarest of the rare factor deficiencies.