Which type of haemophilia is more common? An in-depth guide

September 27, 2025 •

2 min read

Globally, haemophilia A is approximately four times more prevalent than haemophilia B. This inherited bleeding disorder raises many questions for families, with 'Which type of haemophilia is more common?' being a frequent concern for those newly navigating the condition and seeking clarity.

Quick Summary

Haemophilia A, also known as classic haemophilia or factor VIII deficiency, is the most common form of this hereditary bleeding disorder. It affects significantly more people than haemophilia B, which is caused by a deficiency of factor IX.

Key Points

Prevalence: Haemophilia A is about four times more common than haemophilia B, affecting more males globally.
Missing Factor: Haemophilia A is caused by a deficiency of clotting factor VIII, while haemophilia B results from a deficiency of factor IX.
Genetics: Both are X-linked recessive disorders, but haemophilia A can have different genetic mutation profiles.
Inhibitor Risk: Inhibitor development is a more frequent complication in severe haemophilia A patients compared to those with haemophilia B.
Management: Despite the difference in prevalence, both types are treated with factor replacement therapy and are best managed by comprehensive care centers.

Understanding the Basics of Haemophilia

Haemophilia is a rare, inherited bleeding disorder where blood doesn't clot properly due to a lack of specific clotting factors. This can cause prolonged bleeding and, in severe cases, spontaneous bleeding into joints and organs. It mainly affects males, and while there's no cure, treatments allow for a full life.

There are several types of haemophilia, with A and B being the most common. They have similar symptoms but are caused by deficiencies in different clotting factors.

The Answer: Haemophilia A is More Common

Haemophilia A is significantly more common than Haemophilia B. Data shows that Haemophilia A is estimated at 12 cases per 100,000 U.S. males (factor VIII deficiency), while Haemophilia B is estimated at 3.7 cases per 100,000 U.S. males (factor IX deficiency). Worldwide, Haemophilia A accounts for about 80% to 85% of cases.

Delving Deeper: Comparing Haemophilia A and B

Both are inherited through an X-linked recessive pattern and share similar symptoms. However, key differences exist:

Genetic Variations

Mutations causing Haemophilia A and B are on the F8 and F9 genes on the X chromosome. The larger F8 gene might lead to more spontaneous mutations.

Clinical Severity

Some studies suggest severe Haemophilia B might be clinically less severe than severe Haemophilia A, with potentially fewer bleeding episodes and less factor concentrate needed in B cases.

Inhibitor Development

Inhibitor development, a complication neutralizing infused factor, is far more common in Haemophilia A (20-30% in severe cases) than in Haemophilia B (under 3%).

Comparison Table: Haemophilia A vs. Haemophilia B


Feature	Haemophilia A	Haemophilia B
Missing Factor	Clotting Factor VIII (FVIII)	Clotting Factor IX (FIX)
Common Name	Classic Haemophilia	Christmas Disease
Prevalence	Approximately 1 in 5,000 males	Approximately 1 in 25,000-30,000 males
Frequency	More common (3-4 times more frequent)	Less common
Genetic Locus	F8 gene (X chromosome)	F9 gene (X chromosome)
Inhibitor Risk	20-30% risk in severe cases	Less than 3% risk in severe cases
Clinical Severity	Potentially more severe in clinical outcome	May be clinically milder in severe cases
Treatment Factor	Recombinant Factor VIII	Recombinant Factor IX

Treatment and Management

Treatment aims to replace the missing factor, either preventatively or on-demand. Haemophilia A uses factor VIII replacement, including newer non-factor options like emicizumab. Haemophilia B uses factor IX replacement. Gene therapies are also emerging.

The Importance of Comprehensive Care

Care at a specialized Hemophilia Treatment Center (HTC) is crucial, involving a multidisciplinary team. For resources, the National Hemophilia Foundation is valuable.

Conclusion

Haemophilia A is significantly more common than Haemophilia B. Both are distinct inherited bleeding disorders with similar symptoms but different factor deficiencies and nuances like inhibitor risk. Lifelong management and advancements in treatment continue to improve lives for those affected.

Frequently Asked Questions

The main difference lies in the specific clotting factor that is deficient. Haemophilia A is caused by a deficiency of clotting factor VIII, whereas haemophilia B is caused by a deficiency of clotting factor IX.

The symptoms for both types are very similar, including prolonged bleeding, easy bruising, and internal joint and muscle bleeds. The severity of symptoms depends on the level of the deficient clotting factor, not the type.

While the severity of both haemophilia A and B is classified as mild, moderate, or severe based on factor levels, some research suggests that severe haemophilia B may be clinically milder than severe haemophilia A in terms of bleeding frequency.

Diagnosis is confirmed through specific factor assays that measure the level of factor VIII and factor IX in the blood, along with genetic testing.

Not necessarily. While haemophilia A is more common, the seriousness of the disease for an individual depends on the severity level (mild, moderate, or severe), which is determined by their specific factor levels, not the type itself.

Yes, the treatments are type-specific. Haemophilia A is treated with factor VIII replacement, while haemophilia B requires factor IX replacement. Other therapies like emicizumab or gene therapy may also be type-specific.

Knowing the prevalence helps with understanding the public health burden of each condition and aids in resource planning and targeted research. It is also a fundamental piece of information for education and awareness.