Prevalence Estimates for Hemophilia in the U.S.
Estimates for the number of people with hemophilia in the United States are largely based on data from federally funded Hemophilia Treatment Centers (HTCs). The CDC, using data from 2012–2018, estimated up to 33,000 males in the U.S. had hemophilia. These surveillance programs are the most reliable source for available figures.
Hemophilia A is the most prevalent type of hemophilia, accounting for roughly 80% of cases and being about four times more common than hemophilia B. Applying this percentage to the overall estimate of 33,000 males suggests approximately 26,400 males have hemophilia A. The CDC also provides a prevalence rate specifically for hemophilia A, estimating 12 cases per 100,000 U.S. males.
Historically, data collection has focused on males due to the X-linked nature of the disorder, leading to an underestimation of the total affected population, particularly females. While hemophilia A is rare, thousands of individuals and families are impacted.
Gender Differences and Diagnostic Challenges
Hemophilia A is an X-linked recessive disorder. Males, with one X chromosome, are more likely to show symptoms. Females, with two X chromosomes, are usually carriers but can still experience bleeding symptoms, often classified as mild hemophilia, due to random X chromosome inactivation. Many females with hemophilia remain undiagnosed until later in life. A 2021 study of HTC data identified around 1,700 women and girls with hemophilia, but this is likely an undercount as many do not use these specialized centers.
Challenges in counting the total population include:
- Underdiagnosis in females: Mild or moderate symptoms are often overlooked.
- Mild cases: Some individuals with mild hemophilia may not be diagnosed without a major medical event.
- Reliance on HTC data: Data from HTCs doesn't capture everyone receiving care elsewhere.
- Historical factors: Higher mortality rates in the past due to contaminated blood products have influenced current population demographics.
A Comparison of Hemophilia A and Hemophilia B
| Feature | Hemophilia A | Hemophilia B |
|---|---|---|
| Cause | Deficiency in clotting factor VIII | Deficiency in clotting factor IX |
| Prevalence | Roughly 80% of all hemophilia cases; ~12 cases per 100,000 males | Roughly 20% of all hemophilia cases; ~3.7 cases per 100,000 males |
| Frequency | About 4 times more common | About 4 times less common |
| Inheritance | X-linked recessive, located on the F8 gene | X-linked recessive, located on the F9 gene |
| Incidence | ~1 in 5,617 male births | ~1 in 19,283 male births |
The Path to More Precise Estimates
Efforts like the CDC's Community Counts program and the national HTC network are working to collect more complete data on the hemophilia population. Advances in genetic testing and increased awareness among healthcare providers are also helping to diagnose more individuals, including females with mild forms. The National Bleeding Disorders Foundation is a valuable resource for information on bleeding disorders.
Conclusion
While determining the exact number of people with hemophilia A in the United States is complex, current estimates derived from specialized treatment centers suggest approximately 26,000 diagnosed males. This figure likely underestimates the true total, particularly when considering underdiagnosed females and mild cases. Ongoing surveillance and increased clinical awareness are crucial for a more accurate understanding of hemophilia A's impact on the U.S. population.
