Understanding Hemophilia -- the Basics

What Is Hemophilia?

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

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

  • Hemophilia A -- also called classic hemophilia -- is most common and occurs in about 80% of people with hemophilia.
  • Hemophilia B -- also called Christmas disease -- is less common and occurs in about 20% of people with hemophilia.

Hemophilia A

Hemophilia A results from too little of a plasma protein called factor VIII, which helps blood clot. The greater the deficiency, the more severe the symptoms.

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

Most people who have hemophilia A have moderate or severe symptoms.

Hemophilia B

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 greater the deficiency, the more severe the symptoms.

Recognizing Hemophilia

If there is no family history of hemophilia, an infant would not be tested for the condition. However, if there is a family history of hemophilia, specific tests can be done from an umbilical cord blood sample to see if a newborn infant has hemophilia. In fact, if the family desires, such testing can be done before a child is born.

For moderate or severe hemophilia, doctors and caregivers usually don't see any signs of the condition at birth or even for some time afterward. Symptoms in children may include:

  • Heavy bleeding in a male baby after circumcision
  • Excessive bruising or unusual bleeding during teething
  • Swollen, bruised joints or muscles when learning to walk
  • Frequent falls and bumps

For mild hemophilia, you may not have any noticeable symptoms until you undergo 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.

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Problems Caused by Hemophilia

Internal bleeding resulting 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 occur. Bleeding in a joint can cause scarring in the joint. With repeated bleeds, the joint may lose mobility and becomes susceptible to further bleeding. 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: Blood in the urine may occur on occasion, due to bleeding within the kidneys.
  • Problems breathing: Breathing problems can occur as a result of bleeding into the throat. If not promptly treated, bleeding in the throat can interfere with breathing so much that a patient 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.

What Causes Hemophilia?

Hemophilia is a genetic disease linked to a defective gene on the X chromosome. Chromosomes come in pairs -- women have two X chromosomes while men have one X and one Y chromosome.

A woman who has the defective gene is called a "carrier" -- she carries the disease and can pass it to her children. In most cases, though, the woman has no symptoms of hemophilia. When a woman who is a carrier has a son, the son receives one X chromosome from his mother, so he has a 50% chance of receiving the defective gene (and a 50% chance of receiving a normal copy of the gene). Boys who receive the defective gene have hemophilia. Likewise, when a woman who is a carrier has a daughter, the daughter has a 50% chance of receiving the defective gene and, thus, being a carrier herself.

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Men who have hemophilia do not pass the disease to their sons because boys inherit only a Y chromosome from their father. However, 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 or change has occurred in one of the genes that tells the body how to make factor VIII or factor IX From the time of the mutation, the affected person can transmit the defective gene to his or her children.

WebMD Medical Reference Reviewed by Melinda Ratini, DO, MS on March 28, 2014

Sources

SOURCES:

U.S. Library of Medicine Genetics Home Reference.

National Heart, Lung and Blood Institute.

National Hemophilia Organization.

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