What Causes Hemophilia?

Hemophilia is a lifelong disease usually resulting from a genetic mutation that prevents blood from clotting due to missing or inadequate levels of clotting factor.  Roughly 70% of hemophilia cases are passed down from parents (inherited hemophilia) and 30% occur spontaneously (acquired hemophilia).

Inherited Hemophilia

Inherited hemophilia occurs when the genetic mutation that causes hemophilia is passed on from parent to child. The gene containing instructions for making clotting factor is located on the X chromosome, one of two sex-determining chromosomes. Since males have one X and one Y chromosome, they carry a higher chance of receiving an X chromosome genetic mutation.

Acquired Hemophilia

Acquired hemophilia is not passed on from parents but is an autoimmune disorder in which the body produces antibodies that mistakenly attack clotting factors. Symptoms of acquired hemophilia can be more severe than inherited hemophilia, including “spontaneous bleeding” (bleeding that occurs without cause).

Symptoms of Hemophilia

The primary symptom of hemophilia is excessive bleeding, whether external or internal. This may include frequent nosebleeds, heavy bleeding from an injury, bleeding from dental or surgical procedures, and unusual bleeding after a vaccination.

Symptoms of internal bleeding include blood in the urine or stool, large bruises, and joint pain or swelling. In cases of severe hemophilia, the brain may bleed spontaneously, resulting in symptoms such as double vision, fatigue, vomiting, and prolonged headache.

Severity of Hemophilia

The severity of hemophilia depends on the level or activity of clotting factor in the patient’s blood. Either a percentage of factor activity or the number of international units per milliliter of blood (IU/ml) is used to indicate this level. Normal clotting factor levels range from 50%-150% (0.50-1.5 IU/ml).

Mild Hemophilia

People with mild hemophilia have factor levels ranging from 5%-40% (0.05-0.40 IU/ml) and often do not experience symptoms. In fact, mild hemophilia may remain undiagnosed until a surgical or dental procedure is performed. Mild hemophilia accounts for about 25% of people who have the disease.

Moderate Hemophilia

Moderate hemophilia occurs when factor levels are between 1% and 5% (0.01-0.05 IU/ml). Patients with moderate hemophilia usually experience prolonged bleeding after an injury and may have infrequent spontaneous bleeding episodes. Roughly 15% of people with hemophilia experience moderate symptoms.

Severe Hemophilia

People with severe hemophilia have blood with less than 1% clotting factor activity (0.01 IU/ml). Frequent bleeding episodes (as often as 1-2 times a week) that occur spontaneously, especially in joints, are common in patients with severe hemophilia.

Preventing Disease Complications

A proactive approach to managing hemophilia is important for a patient’s long-term health. This includes making healthy choices and carefully adhering to treatment plans. Patients who take an active role in their treatment regimen can prevent disease complications and enjoy a better quality of life.

Learn more about how NCHS services support hemophilia patients and help them achieve the best possible treatment.