Proper clotting is critical for healing to take place after an injury. When you have an injury to a blood vessel, the first thing the body does is constricts the flow of blood. Then the body sends platelets to plug the hole in the blood vessel wall. These platelets stick together; once this platelet plug is formed, the body sends the clotting factor to the site. All of these blood components work together to make a blood clot. If you are missing or deficient in one of these proteins or platelets, or they do not function properly, a normal blood clot will not form. Uncontrolled bleeding can be painful and can cause long-term consequences. In many cases, there is reasonable treatment. The process that creates this healing clot is called the clotting cascade.

Causes of a Bleeding Disorder

Bleeding disorders are usually genetic. However, they can also be acquired. Bleeding disorders are not contagious. They cannot be caught from someone else or spread like a virus or an infection.

Genetic Causes and Genetics of Bleeding Disorders

Bleeding disorders are usually caused by a genetic mutation; they can be inherited in different ways (depending on the type of bleeding disorder):

X-Linked Heredity

Some bleeding disorders, such as hemophilia, are X-linked. This means that the genetic defect that causes hemophilia is on the X chromosome. (Chromosomes are genes.) Women have two X chromosomes, and men have an X and a Y chromosome. Because women have two X chromosomes, some women are asymptomatic carriers if the hemophilia gene is on one X chromosome, and the other X chromosome is healthy and takes over. Men, however, only receive one X chromosome, so if they receive the affected gene, they will have hemophilia.

Which chromosome the man provides determines the gender of a baby. (If he provides an X chromosome, the baby will be girl, and if he provides a Y chromosome, the baby will be a boy.) If a man with gives his X chromosome to the baby (she will get her second X from her mother), she will be a carrier of hemophilia. Therefore, all daughters of hemophiliac men are “obligate” carriers. Some carriers have a low factor level themselves and have mild hemophilia. Because a man with hemophilia provides a son with a Y chromosome, and the Y chromosome does not carry the hemophilia gene, sons of hemophiliacs do not have hemophilia. A female carrier of hemophilia has a 50% chance of passing the bleeding disorder on to a son or daughter. The son could have hemophilia, or the daughter could be carrier like her mother.

Autosomal Dominant

Autosomal dominant heredity means that if either biological parent has a genetic defect for a particular bleeding disorder, their child could be born with it.

Genetic Mutation

Some bleeding disorders are caused by spontaneous genetic mutations. (Hemophilia is approximately 30%.) This means that there is no family history. However, once the mutation occurs, it will be carried forward in future generations. The mutation may occur in the patient or in either biological parent.

Genetic Testing and Counseling

If you have an inherited bleeding disorder in your family, you might want to consider genetic testing and/or counseling. (Once a spontaneous mutation occurs, it will be inherited from then on.) You can find a genetic counselor through your HTC or at www.nsgc.org. Genetic counseling can help you plan better for the possibility of having a child with a bleeding disorder.

Non-Genetic Causes

Although bleeding disorders are usually genetic, there are some non-genetic things that can cause bleeding. For example, some medications can cause bleeding, and this would be considered side effects more than an actual bleeding disorder:

• Anticoagulants
• Long-term use of some antibiotics, including penicillin
• Medications such as aspirin, ibuprofen, other anti-inflammatory drugs
• Phenothiazines
• Long-term use of prednisone.

Other things that can cause bleeding and mimic congenital bleeding disorders include the following:

• Liver transplant: If you receive a liver from a donor who had hemophilia but didn’t know it.
• Illnesses: Illnesses that cause a vitamin K deficiency or severe liver disease.
• Vitamin K deficiency: Most common in babies and can be managed by a vitamin K shot at birth.
• If your body forms antibodies that fight against the blood’s natural clotting factors
• Renal failure.

As we look to the future of the bleeding disorders community, we must remember the past. Blood Roots, a powerful documentary tells the story of the advancements in treatment from the perspective of the dedicated staff at Hemophilia Treatment Centers.