Understanding Hemophilia: How Rare is Hemophilia and What Are the Facts?

October 1, 2025 •

3 min read

While often considered a rare genetic disorder, hemophilia A affects approximately 1 in 5,000 live male births, while hemophilia B affects about 1 in 20,000 live male births globally. Understanding how rare is hemophilia involves examining different types and severity levels of this bleeding disorder, with global estimates suggesting over a million people may be affected worldwide.

Quick Summary

Hemophilia is a rare genetic bleeding disorder affecting different numbers of individuals depending on the type and sex. Hemophilia A is more common than hemophilia B, but both are considered rare. Prevalence varies globally, often impacted by diagnosis rates, especially in lower-income regions.

Key Points

A Rare Genetic Disorder: Hemophilia is a rare genetic bleeding disorder, though prevalence differs significantly between its types and geography.
Hemophilia A vs. B: Hemophilia A is roughly four times more common than Hemophilia B, with specific incidence rates tied to male births.
X-Linked Inheritance: The most common forms are X-linked recessive, explaining why males are predominantly affected, while females are more often carriers.
Severity Levels Vary: The severity of hemophilia (mild, moderate, or severe) is determined by the level of clotting factor activity in the blood.
Diagnosis Varies by Income: There is a stark difference in age of diagnosis and access to care between low- and high-income countries, as documented by the World Federation of Hemophilia.
Spontaneous Mutations Occur: About one-third of cases are due to a new, spontaneous genetic mutation with no prior family history.
Underdiagnosis Exists: Global estimates suggest many people with hemophilia, especially in low-resource settings, remain undiagnosed.
Improved Care Improves Outcomes: Access to specialized treatment centers and regular prophylactic care significantly improves the prognosis for people with hemophilia.

Hemophilia is a group of rare, inherited bleeding disorders characterized by the blood's inability to clot properly due to a deficiency or defect in clotting factors. The severity is determined by the amount of clotting factor present, classifying individuals as having mild, moderate, or severe hemophilia. The most common types, hemophilia A and hemophilia B, are caused by deficiencies in factor VIII and factor IX, respectively, and are inherited in an X-linked recessive pattern. While considered rare, recent data indicates that the number of people affected globally is likely higher than previously believed.

Breaking Down the Rarity: Hemophilia by the Numbers

Prevalence statistics for hemophilia vary geographically and by type, with underdiagnosis being a significant factor, particularly in lower-income countries.

A 2019 study estimated the global hemophilia population to be over 1.1 million, a substantial increase from older estimates, attributed to improved data collection. The World Federation of Hemophilia (WFH) works to enhance diagnosis rates, which differ considerably between countries. In the U.S., the CDC estimates that 30,000 to 33,000 males live with hemophilia. The incidence among U.S. male births is 1 in 5,617 for hemophilia A and 1 in 19,283 for hemophilia B. Hemophilia C, caused by factor XI deficiency, is much rarer, with an incidence of about 1 in 100,000 people, and affects both sexes equally, being more common in people of Ashkenazi Jewish descent.

The Difference Between Types of Hemophilia


Feature	Hemophilia A	Hemophilia B
Missing Clotting Factor	Factor VIII	Factor IX
Nickname	Classic hemophilia	Christmas disease
Incidence in Male Births (U.S.)	~1 in 5,617	~1 in 19,283
Relative Rarity	About four times more common than Hemophilia B	Four times less common than Hemophilia A
Inhibitor Risk	Higher risk (approx. 20% of severe cases)	Lower risk (less than 3% of cases)

The Role of Genetics in Hemophilia

Most hemophilia cases are inherited, although some result from new spontaneous mutations. Hemophilia A and B follow an X-linked recessive inheritance pattern. This means the affected gene is on the X chromosome. Males, having one X chromosome, develop the condition if they inherit the altered gene from their mother. Females, with two X chromosomes, are typically carriers and less likely to be symptomatic unless they inherit two altered genes or have significantly skewed X-chromosome inactivation. Notably, about one-third of individuals with hemophilia lack a family history, indicating a new genetic mutation.

Understanding Hemophilia Severity Levels

Hemophilia severity is categorized based on the percentage of normal clotting factor activity:

Severe Hemophilia: Less than 1% clotting factor, leading to frequent spontaneous bleeding.
Moderate Hemophilia: 1% to 5% clotting factor, causing bleeding after minor injuries or sometimes spontaneously.
Mild Hemophilia: 6% to 49% clotting factor, with bleeding typically occurring only after significant injury or surgery. Mild cases can sometimes be diagnosed later in life.

Access to Care and Diagnosis Disparities

Data from the World Bleeding Disorders Registry highlights significant global disparities in hemophilia care and diagnosis, largely influenced by economic factors. In lower-income countries, the median age of diagnosis for severe hemophilia is higher than in high-income countries, although it has improved in recent years. Delayed diagnosis and limited access to preventive treatment in these regions contribute to increased bleeding, disability, and reduced life expectancy. Specialized Hemophilia Treatment Centers (HTCs) provide comprehensive care and are associated with better patient outcomes. The WFH offers humanitarian aid to improve access to diagnosis and treatment in areas with limited resources.

Conclusion

Addressing how rare is hemophilia, it is indeed a rare genetic disorder, though recent global data suggests a higher prevalence than previously estimated due to improved diagnosis. Prevalence varies by type, with Hemophilia A being more common than B, and both primarily affecting males due to their X-linked inheritance. Significant global disparities exist in diagnosis and access to care, which organizations like the WFH are working to address to ensure timely and effective treatment for all individuals with hemophilia. Advancements in treatment and increased access to care have significantly improved the outlook for those living with this condition.

Frequently Asked Questions

In the United States, the Centers for Disease Control and Prevention (CDC) estimates the incidence of Hemophilia A is approximately 1 in 5,617 live male births, while Hemophilia B occurs in about 1 in 19,283 live male births.

The most common types of hemophilia (A and B) are X-linked recessive disorders, meaning the gene is on the X chromosome. Since males have only one X chromosome, a single altered gene is enough to cause the condition. Females, with two X chromosomes, would need two altered genes or have significant skewed X-inactivation to show symptoms.

Yes, although it is much rarer. Females can inherit hemophilia by inheriting an altered gene from both parents or through a process called skewed X-inactivation, where the X chromosome with the normal gene is turned off in more than half of the body's cells.

Yes, Hemophilia C is extremely rare, affecting about 1 in 100,000 people globally. It is distinct from hemophilia A and B because it is autosomal recessive, meaning it affects males and females equally.

Diagnosis rates significantly impact our understanding of rarity. In low- and lower-middle-income countries, diagnosis is often delayed or missed entirely due to limited resources, meaning the reported prevalence is lower than the actual number of people affected.

Hemophilia A, also known as classic hemophilia, is the most common type and is caused by a deficiency of clotting factor VIII. It is about four times more common than Hemophilia B.

No, severity does not affect population rarity, but it can affect diagnosis rates. Milder forms of hemophilia may go undiagnosed for many years or even until adulthood because bleeding episodes only occur after serious injury or surgery.

Based on a CDC study using data from 2012–2018, it is estimated that between 30,000 and 33,000 males are living with hemophilia in the United States.