What is Hemophilia?
Hemophilia is an inherited disease most commonly effecting males that is characterized as a deficiency of a protein affecting the ability of the blood to clot. People with this condition experience prolonged bleeding or oozing following an injury, surgery, or having a tooth pulled. In severe cases of hemophilia, continuous bleeding occurs after minor trauma or even in the absence of injury (spontaneous bleeding). Serious complications can result from bleeding into the joints, muscles, brain, or other internal organs. Milder forms of hemophilia do not necessarily involve spontaneous bleeding, and the condition may not become apparent until abnormal bleeding occurs following surgery or a serious injury.
Types of Hemophilia
Hemophilia A (also known as classic hemophilia or factor VIII deficiency) is characterized by a missing or defective Factor VIII clotting protein. How frequently a person bleeds and the severity of those bleeds depends on how much FVIII is in the plasma, the straw-colored fluid portion of blood.
Hemophilia B (also known as Christmas disease or factor IX deficiency) is characterized by a missing or defective Factor IX clotting protein. How frequently a person bleeds and how serious the bleeds are depends on how much FIX is in the plasma.
For information on other more rare types of hemophilia including Factor VII, Factor XI, or Factor XIII, please visit www.hemophilia.org
For more information about genetic bleeding disorders, please visit the HANDI page of the NHF website.
Levels of Severity
Normal plasma levels of Factor VIII range from 50% to 150%. Levels below 50%, or half of what is needed to form a clot, determine a person’s symptoms.
Mild hemophilia A: 6% up to 49% of Factor VIII in the blood.
Mild hemophilia B: 6% up to 49% of Factor IX in the blood.
People with mild hemophilia A or B generally experience bleeding only after serious injury, trauma or surgery. In many cases, mild hemophilia is not diagnosed until an injury, surgery or tooth extraction results in prolonged bleeding. The first episode may not occur until adulthood. Women with mild hemophilia often experience heavy and/or lengthy menstrual periods, and can hemorrhage after childbirth.
Moderate hemophilia A: 1% up to 5% of Factor VIII in the blood.
Moderate hemophilia B: 1% up to 5% of Factor IX in the blood.
People with moderate hemophilia A or B tend to have bleeding episodes after injuries. Bleeds that occur without obvious cause are called spontaneous bleeding episodes.
Severe hemophilia A: <1% of Factor VIII in the blood.
Severe hemophilia B: <1% of Factor IX in the blood.
People with severe hemophilia A or B experience bleeding following an injury and may have frequent spontaneous bleeding episodes, often into their joints and muscles.
Percentage Breakdown of Overall Hemophilia Population by Severity
Severe (factor levels less than 1%) represent approximately 60% of cases
Moderate (factor levels of 1-5%) represent approximately 15% of cases
Mild (factor levels of 6%-30%) represent approximately 25% of cases
Genetics of Hemophilia
The responsible gene for hemophilia is on the X chromosome. Males inherit an X chromosome from their mother and a Y chromosome from their father. (Male = XY) Females inherit an X chromosome from their mother and an X chromosome from their father. (Female = XX).
The graph below illustrates the genetic possibilities of inheriting hemophilia. Hemophilia is illustrated in red. With each birth, the child has a 50/50 chance of inheriting the disorder if one parent has the gene.