Hemophilia is a blood clotting disorder that can be inherited. Caused by changes in the X chromosome, hemophilia is an autosomal recessive genetic disorder.
Hemophilia is a genetic disorder that affects the clotting factors in the blood. If you have hemophilia, your blood does not clot as it typically would. You may experience significant bleeding with surgery or trauma.
Here’s how hemophilia is inherited, who is more likely to have the disorder, and what tests may help with diagnosis.
Hemophilia A, also called factor VIII deficiency, and hemophilia B, also called factor IX deficiency, are inherited on the X chromosome in an autosomal recessive pattern. This means that you must inherit one affected X chromosome to have the condition — in this case, hemophilia.
Generally, individuals have either two X chromosomes or one X and one Y chromosome. These chromosomes determine sex characteristics, such as if you produce eggs or sperm, have a penis or a vagina, and many other traits.
If you have a Y chromosome, you are
If you have two X chromosomes, you may be hemophilia carriers. If you inherit one affected gene, you may be a carrier but may not have the disorder. You must inherit two affected X chromosomes to develop it, making hemophilia
There are three scenarios for how a person may inherit affected genes.
Parent with XX chromosomes carries an affected gene
If the parent with XX chromosomes is the carrier of the affected gene and the parent with XY chromosomes does not, their children with XY chromosomes have a
Parent with XY chromosomes has hemophilia
If the XY parent has hemophilia and passes on the affected gene, each of their XY children has a
Both parents have affected genes
If both parents carry affected genes, each of their XY chromosome children has a
Your doctor may suggest genetic testing if you or your partner have a family history of hemophilia. Before becoming pregnant, this can be done with a blood test. Your doctor will take a blood sample and send it to a laboratory to analyze the clotting factors.
During pregnancy, your levels of factor VIII will
Symptoms may appear soon after birth or within the
Additional symptoms over time:
- swelling or tightness in and around joints from bleeding into the joints
- bruising (hematoma) from bleeding into the skin or other soft tissues
- bleeding inside the mouth and gums or after losing teeth
- bleeding after vaccinations or other tests and injections performed with needles
- bleeding into the stool (may look red, tarry, or black) or urine (may be tinged red)
- bleeding from the nose (nosebleeds) that happens
Blood tests are the primary means of diagnosis if a person is experiencing symptoms of hemophilia.
Hemophilia is treated by replacing the blood clotting factor, a protein that is missing from the blood. Treatments include injecting clotting factor concentrates into a person’s blood through their veins.
These treatments can be used episodically to help specific bleeding episodes or prophylactically to prevent future bleeding episodes.
Other treatment options:
People with hemophilia may need treatment throughout life to prevent bleeding episodes. They may also need additional monitoring as they age.
That said, life expectancy for people with hemophilia may be similar to that of the general population. In one
How common is hemophilia?
Hemophilia A is
Why do people with XY chromosomes not pass hemophilia onto their offspring with XY chromosomes?
People with XY chromosomes do not inherit an X chromosome from their XY parent. Instead, they inherit the Y chromosome, which does not carry the disorder.
Is hemophilia always genetically inherited?
Hemophilia is inherited on the X chromosome. Having this disorder or carrying it does not guarantee that your child will inherit the affected genes.
If you have a family history of this disorder, make an appointment with your doctor. You may be referred to a genetic counselor so you can better understand the potential risks.