Hemophilia

Hemophilia is passed down from parents to children.

Yes, hemophilia is a sex-linked disorder. The X and Y sex chromosomes help determine hemophilia inheritance patterns. The gene for hemophilia is carried on the X chromosome.

Hemophilia is inherited in an X-linked recessive manner. Females inherit two X chromosomes, one from their mother and one from their father (XX). Males inherit an X chromosome from their mother and a Y chromosome from their father (XY). That means if a son inherits an X chromosome carrying hemophilia from his mother, he will have hemophilia. It also means that fathers cannot pass hemophilia on to their sons. But because daughters have two X chromosomes, even if they inherit the hemophilia gene from their mother, most likely they will inherit a healthy X chromosome from their father and not have hemophilia. A daughter who inherits an X chromosome that contains the gene for hemophilia is called a carrier. She can pass the gene on to her children. Many women who carry the hemophilia gene also have low factor expression, which can result in heavy menstrual bleeding, easy bruising, and joint bleeds.

Some women who have the hemophilia gene have factor expression low enough to be diagnosed with hemophilia.

Severe (factor levels less than 1%)

Moderate (factor levels of 1-5%)

Mild (factor levels of 6%-30%)

People with hemophilia bleed longer than other people. Bleeds can occur internally, into joints and muscles, or externally, from minor cuts, dental procedures, or injuries. How often a person bleeds, and the severity of those bleeds depends on how much factor a person produces naturally.

Normal levels of factor range from 50% to 150%. Levels below 50% – or half of what is needed to form a clot – determine a person’s symptoms.

Doctors will perform tests that evaluate how long it takes for the blood to clot to determine if someone has hemophilia. A clotting factor test, called an assay, will show the type of hemophilia and the severity, or how much clotting factor the person produces on their own.

Because of our understanding of hemophilia genetics, most people who have a family history of hemophilia will ask that their baby boys be tested soon after birth to see if they have hemophilia. If there is no family history of hemophilia, people often notice bleeding that takes longer to stop or lots of bruising. Many babies born with severe hemophilia are diagnosed if there is prolonged bleeding after circumcision.

For girls, it often takes seeing worsening of symptoms for the diagnosis process to begin. Most girls are not tested for hemophilia before puberty. Heavy periods are a symptom of a bleeding disorder in women and girls. If there is a known family history, it is important to monitor for symptoms. It is recommended that women who have a family history of hemophilia get tested before getting pregnant, to help prevent complications during childbirth.

The best place for patients with hemophilia to be diagnosed and treated is at one of the federally funded hemophilia treatment centers (HTCs) that are spread throughout the country. HTCs provide comprehensive care from skilled hematologists and other professional staff, including nurses, physical therapists, social workers and sometimes dentists, dietitians and other healthcare providers, including specialized labs for more accurate lab testing.

Most treatments for hemophilia focus on replacing the missing protein, so a person can form a clot, to reduce or eliminate the bleeds associated with the disorder. Treatments that work to prevent bleeding through new mechanisms have recently come to the market or are undergoing evaluation in research studies. People with hemophilia have several different medication options for treatment.