What is the difference between Hemophilia A and Hemophilia B?

Hemophilia is a rare inherited bleeding disorder that prevents blood from clotting properly. There are two main, common types of hemophilia: Hemophilia A and Hemophilia B, and the primary difference between them lies in the specific clotting factor that the body is missing or has low levels of.

In Hemophilia A, the deficiency or defect is in clotting factor VIII (Factor VIII), while in Hemophilia B, the deficiency or defect is in clotting factor IX (Factor IX) [1]. Both factors are essential for the normal blood clotting process, and any deficiency in them leads to excessive bleeding after injuries or surgery, and spontaneous bleeding may occur inside the body, especially in joints, muscles, and organs [1].

Understanding Clotting Factors

Clotting factors are proteins in the blood that help form clots to stop bleeding. When an injury occurs, these factors work together in a series of reactions to form a stable blood clot [3]. People with hemophilia have low levels of one of these factors, either factor VIII or factor IX [1].

The severity of hemophilia is determined based on the amount of clotting factor present in the blood; the lower the amount, the more likely and more dangerous bleeding becomes [2]. Hemophilia A is three to four times more common than Hemophilia B [2].

Causes and Genetics

Most cases of hemophilia are inherited and result from a change (mutation) in one of the genes responsible for producing clotting factor proteins [1]. These genes are located on the X chromosome [2].

• Males: Have one X chromosome (from the mother) and one Y chromosome (from the father). They can develop hemophilia if their only X chromosome carries the genetic change [1].
• Females: Have two X chromosomes (one from the father and one from the mother). They typically only develop hemophilia if both X chromosomes carry the genetic change, or if one carries the change and the other is missing or inactive [1]. Females who carry the genetic change on one X chromosome are considered "carriers" of the disease, may exhibit some symptoms, and can pass the gene to their children [1].

In rare cases, hemophilia can develop later in life, known as acquired hemophilia, where the body produces antibodies that attack and disable the clotting factor [1].

Diagnosis

To diagnose hemophilia and determine its type and severity, doctors perform specific blood tests [2]. These tests include:

• Factor Assays: These tests measure the levels of clotting factors in the blood and show whether there is a deficiency or defect in factor VIII (for Hemophilia A) or factor IX (for Hemophilia B) [3].
• Medical and Family History: The doctor will ask about symptoms and the family history of the disease [1].
• Physical Examination: To look for signs of hemophilia such as bruising [1].

Genetic testing can be conducted to identify carriers or to diagnose a fetus during pregnancy or a newborn [1].

Treatment and Management

The primary goal of treating Hemophilia A and B is to replace the missing clotting factor to enable blood to clot properly [2]. This is usually done by injecting the replacement clotting factor into a vein [1]. The replacement clotting factor can be made from donated blood plasma or manufactured in a laboratory (recombinant factor) [1].

In severe cases, patients may receive the replacement factor regularly to prevent bleeding episodes (prophylactic treatment) [1]. Patients can learn how to inject the factor themselves at home [1].

Other treatments are available for Hemophilia A, such as non-factor products that mimic the function of factor VIII or prevent clots from breaking down [2]. Gene therapy is also an option for both Hemophilia A and B, where copies of the gene are injected to help the body produce more of the clotting factor [2].

If bleeding causes joint damage, physical therapy may help improve function [1]. It is recommended to obtain high-quality medical care from specialists at comprehensive hemophilia treatment centers (Hemophilia: Understanding the Inherited Bleeding Disorder and Managing Life With It (Arabic)) to prevent serious complications [2].

When to Seek Emergency Care?

Emergency care should be sought immediately if a brain hemorrhage is suspected, which can be life-threatening and cause brain damage [1]. Symptoms of a brain hemorrhage include severe headache, sudden weakness, vision problems, or changes in consciousness. Attention should also be paid to any bleeding that does not stop with direct pressure, bleeding in the joints causing severe swelling and pain, or the presence of blood in the urine or stool [1].

Medical references

• Hemophilia
• About Hemophilia
• Coagulation Factor Tests