Inherited bleeding disorders mean that the disorder is passed from biological parents to their child. Each person inherits chromosomes from their biological parents. Chromosomes are made up of DNA and are the location of your genes. If a person inherits a gene that does not work the way it should, then depending on how the disorder is inherited, a person could be affected by the disorder or be a carrier of the disorder. If you want to find out whether you are the carrier of a specific inherited disorder, you can receive genetic testing. Genetic testing is important both for family planning purposes and for your personal health.
This section of Steps for Living covers:
Who Should Be Tested for Carrier Status?
How Do You Become a Carrier?
Bleeding disorders happen when a gene that tells your body to make the proteins and platelets needed to form a blood clot does not work the right way. Without a gene that works properly, the clotting proteins or platelets in your body may be missing, low, or not working well. Bleeding disorders can have an X-chromosome linked, autosomal recessive, or autosomal dominant inheritance pattern. Each of these inheritance patterns will have a different effect on how a person becomes a carrier. However, regardless of the disorder and your genetic status, if you have bleeding symptoms, you should seek and receive treatment.
If a biological parent carries the gene that causes the disorder, then there is a 1 in 4 chance that their child will be:
- A female assigned at birth who does not carry the gene for the disorder (25% chance)
- A female assigned at birth who carries the gene for the disorder (25% chance)
- A male assigned at birth without the disorder (25% chance)
- A male assigned at birth with the disorder (25% chance)
Female assigned at birth carriers have a 50% (1 in 2) chance of passing the disorder on to a child with each pregnancy. Males assigned at birth that have the defective gene, pass the condition on to all their children assigned female at birth but not to children assigned male at birth.
- If one parent is affected and one parent is not affected, 100% of their children will be carriers.
- If one parent is a carrier and one parent is unaffected, then each of their children has a 50% chance of being a carrier and a 50% chance of being unaffected.
- If both parents are carriers, then each of their children has a 25% chance of being affected, a 25% chance of being unaffected, and a 50% chance of being a carrier.
- If one parent is a carrier, and one parent is affected, then each of their children has 50% chance of being a carrier and a 50% chance of being affected.
Sometimes there is no family history of a bleeding disorder. In this case the parents did not pass an affected gene to their child, and the parent is not a carrier. Instead, the bleeding disorder is caused by a new change in a gene, called a spontaneous mutation. For some bleeding disorders, a person can also acquire the disorder throughout their life.
If you want more information about genetics and bleeding disorders, please go to How Does a Person Get a Bleeding Disorder.
Who Should Be Tested for Carrier Status?
The National Bleeding Disorder's Foundation Medical and Scientific Advisory Council (MASAC) recommends that people who are at risk of being a carrier be given diagnostic testing, pre- and post-test counseling, and reproductive options. Testing clotting factor levels can be a first step to find out if you are a carrier of a disorder. Someone who is a carrier may have low levels of factor.
There is no right age for genetic or other testing. Some people or families may delay testing. Other people or families might test a child early, especially if they have signs and symptoms of a bleeding disorder. Some people may not be tested until after puberty or when a child is old enough to make an informed decision. For people considering pregnancy, testing before pregnancy might be more reliable. Clotting factor levels rise during pregnancy, making tests results unreliable.
Genetic testing and counseling can provide valuable information for people and their families. These tests can help people manage their own health, make reproductive decisions, and talk with other family members who also may be affected and want to be tested. If you want more information about family planning, please go to Family Planning.
If you want more information about the recommendations on diagnosis and management of bleeding disorders for women, girls, and those with the potential to menstruate, please go to MASAC Guidelines #264.
What Are the Types of Tests?
There are many types of tests available, including DNA testing, testing for factor levels, and prenatal testing. Keep in mind that results from genetic tests may not be available for several weeks. If you have any questions about genetic or other testing, talk with your health care provider or Hemophilia Treatment Center (HTC).
Below is information on the types of tests and support available:
The most accurate way to tell the carrier status is to examine the DNA for genetic changes. There are 2 types of DNA testing available.
- Direct Mutation Testing
For some disorders, it is possible to look for mutations in the genes. This approach is called direct mutation testing and is the most accurate way for identifying carriers. A blood sample from a person with the bleeding disorder is checked first. In many cases, a mutation can be identified.
Next, a blood sample from the potential carrier is checked for the specific mutation. If the mutation is found than the person is a carrier. If the mutation is not found, then in most cases the person is not a carrier. In rare cases a person’s eggs but not their blood cells have the mutation. This testing is performed at specialized laboratories. Typically, results are available in a few weeks. - Linkage (Indirect Testing)
In some cases a gene mutation cannot be identified. Using indirect testing (called linkage testing) may help determine the gene carrier status by tracking the gene in the family. To perform this test, blood samples are taken from affected people and other family members. Patterns of linked DNA in the person with the bleeding disorder are compared to the DNA in other family members to check for the same pattern. Linkage testing is not as accurate as direct testing and does not provide information for all families. Talk with a genetic counselor if you have any questions about this type of test.
Coping With Being a Carrier
Learning that you or someone you care for is a carrier can be an emotional and challenging time. How you feel often depends on your experience with a bleeding disorder or if you are already connected to the bleeding disorders community. There is support available from genetic counselors and social workers at a Hemophilia Treatment Center (HTC). You can also join a local or virtual support group or talk with a mental health provider.
How a person deals with the possibility of passing a genetic disorder to a child depends on many factors. Genetic counselors can help with making decisions about parenthood, pregnancy, childbirth, and raising a child with a chronic health condition. You can talk with trusted family members, friends, and mental health providers about the personal and emotional aspects of testing and test results. Health care providers at an HTC can give you information on the health issues, financial matters, and caregiving for a child with a bleeding disorder. Genetic counselors can also help families better understand their emotions and address any concerns.