hemophilia A

What is Hemophilia A?

Hemophilia A, also known as factor VIII deficiency, is a condition that causes prolonged bleeding. It is caused by harmful changes (variants) in the F8 gene. Individuals with hemophilia A do not have enough of an important protein called factor VIII (eight). This protein helps to form blood clots after an injury. Individuals with the condition may experience life-threatening blood loss after an injury or medical procedures. Hemophilia A is an X-linked disease. This means the condition is typically more severe in individuals assigned male at birth (XY). However, individuals assigned female at birth (XX) may also have symptoms of the condition.

Hemophilia A has different levels of severity: severe, moderate, and mild. The symptoms of each level of severity are described below.

Severe hemophilia A

People with this form of the condition typically show symptoms by age two. Without ongoing treatment, they can experience excess bleeding after injury and episodes of spontaneous bleeding into muscles and joints. These episodes can lead to joint pain, swelling, and permanent damage.

Moderate hemophilia A

Individuals with a moderate form of the condition often show symptoms in the first five to six years of life. Individuals with the moderate form also experience prolonged bleeding after injury, but they have less spontaneous bleeding than individuals with the severe form.

Mild hemophilia A

Individuals with mild hemophilia A often only experience prolonged bleeding after severe injury or surgery. These individuals may not be identified as having the condition until late childhood or adulthood. Individuals with the mild form may go years between prolonged bleeding episodes.

Additional considerations for carriers

Most XX individuals (who are typically assigned female at birth) are carriers of hemophilia A. About 30% of carriers will exhibit symptoms. Most symptomatic carriers will have mild hemophilia A, although more severe symptoms are possible.

How common is Hemophilia A?

The incidence of hemophilia A is 1 in 4,000 to 1 in 5,000 in individuals assigned male at birth (XY). Up to one third of individuals with hemophilia A do not inherit a harmful variant (de novo).

How is Hemophilia A treated?

There is no cure for hemophilia A. Treatment for the condition is directed at replacing the missing factor VIII protein in situations where the individuals would need it. This is usually after an injury and before surgery or dental work. Individuals with severe disease may receive factor VIII through an IV more regularly to prevent spontaneous bleeding episodes. People with hemophilia A may be advised to avoid activities that can easily result in injury, such as contact sports. Regular checkups with a physician specializing in treating hemophilia are recommended.

What is the prognosis for an individual with Hemophilia A?

Individuals with hemophilia A can live near-normal life with early detection and treatment. If left untreated, the disease can cause life-threatening complications and increase the risk for chronic joint disease.