Three Types of Hemophilia
Hemophilia is a rare, inherited bleeding disorder in which the blood doesn’t clot normally. Hemophilia patients bleed for a longer time than others after an injury and may also bleed internally, particularly in the knees, ankles and elbows.
According to the U.S. Centers for Disease Control and Prevention, hemophilia A occurs in about one in every 5,000 live births. About 20,000 Americans suffer from hemophilia.
Normally, people are born with a critical protein called “clotting factor,” which helps the blood clot after an injury. People born with hemophilia have little or no clotting factor. There are also 13 types of clotting factor that work with platelets to help the blood clot.
The two main types of hemophilia are A and B, according to the National Hemophilia Foundation. A third, rarer form of the disease is called hemophilia C. Each type is directly related to a specific factor, namely, hemophilia A is a Factor VIII deficiency, hemophilia B is a Factor IX deficiency and hemophilia C is a Factor XI deficiency.
Hemophilia type A
Hemophilia A is a genetic disorder caused by missing or defective Factor VIII protein. It is inherited, but in about one-third of known cases it is caused by a spontaneous genetic mutation.
The blood disorder affects all ethnic groups equally. More than half of all people with hemophilia A have a severe form of the disease.
Hemophilia A is carried by the X chromosome. It is inherited in an X-linked recessive manner. As such, two hemophilia-carrying X chromosomes must be inherited for the disease to be active in women, but only in one X chromosome for men.
A female inherits two XX chromosomes, one from her mother and one from her father (XX). A male inherits an X chromosome and a Y chromosome from her father (XY). This means that if a son inherits an X chromosome from his mother who carries hemophilia, he will have hemophilia. But because women receive two X chromosomes, only if both parents carry the defective gene can they develop the disease.
Hemophilia A has three stages: mild, moderate and severe, depending on the ratio of Factor VIII clotting protein in the blood. Mild hemophilia 6-49 percent, moderate hemophilia is 1-5 percent, and severe is less than 1 percent.
People with hemophilia A bleed longer than others, internally or externally. Those with mild hemophilia A generally bleed only after serious injury, trauma or surgery. Often, the disease is diagnosed after one of these situations due to prolonged bleeding, and the first episode may occur only in adulthood. Women often experience heavy menstrual periods and can hemorrhage after giving birth.
Moderate hemophilia patients tend to have more frequent bleeding episodes after less important injuries, or even spontaneously. In severe cases, bleeding may occur spontaneously in the joints and muscles.
Hemophilia A should be diagnosed and treated at a specialized hemophilia center. Tests that evaluate clotting time and a patient’s ability to form a clot may be ordered. A clotting factor test, called an assay, will determine the type of hemophilia and its severity.
The main treatment for hemophilia A is concentrated Factor VIII product, which is administered intravenously.
Patients with severe hemophilia may be given a routine treatment regimen called prophylaxis to maintain enough clotting factor in their bloodstream to prevent bleeds.
Hemophilia type B
Hemophilia B is a genetic disorder caused by missing or defective Factor IX clotting protein. It is also inherited, and just like hemophilia A, it can be caused by a spontaneous genetic mutation in one-third of the cases. This type of hemophilia also affects all ethnic groups equally, but it is about four times as rare as hemophilia A.
Hemophilia B is also carried in the X chromosome, in an X-linked recessive manner, meaning that two hemophilia-carrying X chromosomes must be inherited for the disease to be active in women, but only in one X chromosome in men.
Females inherit two XX chromosomes, one from their mother and one from their father (XX). Males inherit an X chromosome and a Y chromosome from their father (XY). This means that is a son inherits an X chromosome from his mother that has carries hemophilia, he will have hemophilia. But because women receive two X chromosomes, it’s only if the two carry the defective gene, that they develop the disease.
Severity levels are the same as hemophilia A, as well as symptoms.
Like hemophilia A, hemophilia B should be diagnosed at a specialized medical facility. Tests that evaluate clotting time and a patient’s ability to form a clot may be ordered. A clotting factor test, called an assay, will determine the type of hemophilia and its severity.
In hemophilia B, the most common treatment is the administration of concentrated Factor IX, administered intravenously. Severe cases of hemophilia B will also be on prophylaxis treatment, to maintain Factor IX clotting factor.
Hemophilia type C
Hemophilia C is a genetic disorder caused by missing or defective Factor XI clotting protein. The disease was first recognized in 1953 in patients who experienced severe bleeding after dental extractions.
The incidence of hemophilia C is estimated at one in every 100,000 people in the general population. In Israel, Factor XI deficiency occurs in up to 8 percent of Ashkenazi Jews due to intermarriage. This is because a Factor XI deficiency is inherited in an autosomal recessive pattern, meaning both parents must carry the gene to pass it on to their children. Unlike hemophilia A and B, men and women are affected equally.
Factor XI plays an important role in the clotting cascade, which leads to clotting. It helps generate more thrombin, a protein that converts fibrinogen to fibrin, which traps platelets and helps hold a clot in place.
Unlike hemophilia A and B, symptoms don’t correlate with Factor XI levels in the blood. People with lower levels may bleed less than those with higher levels of Factor XI. Patients often experience nosebleeds or soft tissue bleeds, as well as hemorrhaging after tooth extraction.
Many women may not know they’re deficient in Factor XI until they experience menorrhagia (heavy menstrual periods) or postpartum bleeding. In hemophilia C, joint and muscle bleeds are uncommon.
To diagnose hemophilia C, doctors will order a bleeding time test, platelet function tests, and prothrombin time (PT) and activated partial thromboplastin time (aPTT) tests.
Factor XI concentrates are unavailable in the United States as yet, so doctors normally treat hemophilia C with fresh frozen plasma. But because Factor XI is not concentrated in this treatment, large amounts may be necessary, which can lead to blood clots. This treatment must be administered carefully.
Fibrin glue is also used to maintain clots after mouth bleeds. When combined with fresh frozen plasma, it arrests bleeding after circumcision and hernia repair. Antifibrinolytics are used to control nose bleeds or bleeding after tooth extraction.