Medically Reviewed by Carol DerSarkissian, MD on August 30, 2022
6 min read

Hemophilia refers to a group of inherited disorders that cause unusual bleeding. The bleeding happens because part of the blood -- the fluid part called plasma -- has too little of a protein that helps blood clot.

Symptoms of hemophilia range from more than usual bleeding after trauma, injury, or surgery to sudden bleeding with no apparent cause. There are two common types of hemophilia:

  • Hemophilia A -- also called classic hemophilia -- is most common. About 80% of people with hemophilia have this type. It happens when there’s too little of a plasma protein called factor VIII, which helps blood clot. The less of factor VIII you have, the more serious your symptoms. Most people who have hemophilia A have moderate or severe symptoms.
  • Hemophilia B -- also called Christmas disease -- is less common. It happens in about 20% of people with hemophilia. Hemophilia B results from too little of a plasma protein called factor IX, which helps blood clot. As in hemophilia A, hemophilia B can be mild, moderate, or severe. The less factor IX, the more serious the symptoms. The first person reported in medical books to have the condition had the last name Christmas. It’s also known as the royal disease because members of several European royal families inherited it from Britain’s Queen Victoria.

A rare form of hemophilia is known as hemophilia C, or factor XI deficiency. It’s caused by a lack of the plasma protein called factor XI. People of Ashkenazi Jewish descent are more likely to have it.

Symptoms of hemophilia range from increased bleeding after trauma, injury, or surgery to sudden bleeding with no apparent cause.

In moderate to severe hemophilia, most children have bleeding within their first 18 months of life. Symptoms in infants and children include:

  • Bleeding in the head during birth
  • Swollen, bruised joints or muscles when learning to walk
  • Bleeding into joints spontaneously or from just learning to walk
  • Bruising easily from minor bumps
  • Frequent nosebleeds or gum bleeds from teething or tooth brushing
  • Bloody urine or stools

With mild hemophilia, you may not have symptoms until you have a dental procedure, which may cause you to bleed heavily, or you may not have any unusual bleeding unless you are injured in an accident or have surgery.

Hemophilia is a genetic disease caused by inheritance of a mutated gene on the mother's X chromosome. Though hemophilia can be from a new genetic mutation, it most often runs in families. While women may carry the mutated gene, it is their sons who inherit their single X chromosome from their mothers and are at a 50% risk for hemophilia. Daughters have two X chromosomes, one from each biological parent, so even if a daughter inherits the hemophilia mutation and becomes a carrier, the other X chromosome can provide normal clotting factors.

Men who have hemophilia don’t pass the disease to their sons because boys inherit only a Y chromosome from their father. But men do pass their X chromosome, and thus a defective gene, to each of their daughters, so each of their daughters is a carrier.

If the father has hemophilia and the mother is a carrier, there is a chance the daughter will have hemophilia.

About 70% of people who have hemophilia can trace hemophilia back through their family for multiple generations. In about 30% of newly diagnosed infants with hemophilia, no other family member is known to have had hemophilia. In these cases, a mutation happened spontaneously in the factor VIII or IX gene. The affected person (or new carrier) can then transmit the defective gene to their children.

It’s rare, but some people who aren’t born with hemophilia can develop it as adults. Acquired hemophilia happens when your immune system attacks the proteins that make your blood clot. You may get it when you’re pregnant or if you have an autoimmune disorder or cancer.

Hemophilia is usually diagnosed soon after birth, either because of an unusual amount of bleeding or because there’s a family history of the disease. Tests can be done from an umbilical cord blood sample to see if a newborn infant has hemophilia. If the family desires, such testing can be done before a child is born.

With a mild form of the disease, there may be no reason to suspect you have it until an unusual bleeding episode as an older child or even an adult.

Doctors will test your blood to see how well and how quickly it clots. If there’s a problem, they’ll do a test called a factor assay. It shows which kind of hemophilia you have and how severe it is:

  • Mild hemophilia: 5% to 40% of the normal clotting factor level
  • Moderate hemophilia: 1% to 5% of the normal clotting factor level
  • Severe hemophilia: Less than 1% of the normal clotting factor level


Your doctor will give you medicine to help your blood clot. You may only need it when you have a bleeding episode. Or you may take it on a regular basis to prevent bleeding episodes.

  • Clotting factor replacement. The main treatment for severe hemophilia is an infusion through your vein of either clotting factor VIII for hemophilia A or clotting factor IX for hemophilia B. This may be done at a hospital, or you can learn to do it at home. The medication is either made from donated blood products or manufactured in a lab.
  • Hormone therapy. The drug desmopressin acetate works like a natural hormone that makes your body release more of its own clotting factor. It’s used for people with mild forms of hemophilia A. It can be injected into a vein or delivered as a nose spray.
  • Clot-preserving drugs. These slow the body’s natural process of breaking down clots as wounds heal. You may take them before a dental procedure or for bleeding in the nose and mouth.
  • Plasma infusion. People with hemophilia C may get donated plasma before surgery. In the U.S., there is no approved medicine with concentrated clotting factor XI.

When internal bleeding has damaged your joints, physical therapy may help regain function.

Because it’s a genetic disease, there’s nothing you can do to prevent hemophilia. But you can get genetic testing to see if you’re a carrier before you decide to have a baby. Some parents who have the gene choose in-vitro fertilization so that an embryo can be tested for the disease before it’s implanted.

Internal bleeding from hemophilia may lead to several health problems, including:

  • Joint deformity. People with severe hemophilia may suffer spontaneous bleeding in the joints. People with less severe hemophilia may have bleeding in a joint if they fall or are injured. If joint bleeds are not promptly and adequately treated, joint deformity can happen. Bleeding in a joint can cause scarring in the joint. With repeated bleeds, the joint may lose mobility and result in a permanent limp. The knee, ankle, and elbow joints are most commonly affected. Bleeding into the muscles of the legs can also be severely disabling.
  • Blood in urine. You may have blood in your urine on occasion due to bleeding from the kidneys or bladder. If the bleeding is heavy, you can get blood clots that obstruct urine flow.
  • Problems breathing.Breathing problems can happen from bleeding into the throat, nosebleeds, coughing, or vomiting. If not promptly treated, bleeding in the throat can interfere with breathing so much that you may need to be put onto a ventilator until the bleeding stops and swelling goes down.
  • Brain damage. Bleeding in the brain may cause permanent brain damage and disability or even death. While usually caused by trauma, in very severe cases of hemophilia, these areas may bleed without known injury.