Which are the causes of Haemophilia?

TL;DR: Haemophilia is an inherited bleeding disorder caused by mutations in specific genes that prevent the body from producing enough clotting factors, which are proteins essential for blood coagulation. While the genetic basis of Haemophilia is well-understood, approximately 30% of new cases arise from spontaneous mutations, meaning they occur without a prior family history of the condition.

What causes Haemophilia at a genetic level?

Haemophilia is primarily caused by a genetic mutation on the X chromosome. Because males have only one X chromosome (XY), they are significantly more likely to manifest the disease if they inherit a mutated gene. Females (XX) typically act as carriers; because they have a second, healthy X chromosome, they usually produce enough clotting factor to prevent severe bleeding, though they may still experience mild symptoms. In Haemophilia A, the mutation occurs in the F8 gene, which is responsible for producing Factor VIII. In Haemophilia B, the mutation affects the F9 gene, which creates Factor IX. Think of these clotting factors as "molecular glue"—without them, the body struggles to form a stable plug to stop bleeding after an injury.

Is the cause of Haemophilia always hereditary?

While Haemophilia is classified as a hereditary condition, it is not always passed down from a parent. In about one-third of diagnosed cases, there is no family history of the disorder. This is due to a de novo (spontaneous) mutation that occurs during the formation of the egg or sperm, or during early embryonic development. Once this mutation exists, it can then be passed on to future generations, starting a new family lineage of the condition. Currently, 334 people with Haemophilia have joined the DiseaseMaps.org community, sharing diverse experiences that reflect both familial and spontaneous origins of the disease.

Are there other factors that contribute to the condition?

It is important to distinguish between the primary genetic cause and secondary factors. While the genetic mutation is the definitive cause of congenital Haemophilia, other factors can influence the severity of the disease or the patient's clinical experience:

• Type of mutation: The specific location and nature of the genetic error determine how much functional clotting factor the body can produce, which directly correlates to the severity (mild, moderate, or severe).


• Inhibitor development: Approximately 20-30% of individuals with severe Haemophilia A develop "inhibitors," which are antibodies that mistakenly attack the infused clotting factor medication, making treatment more complex.


• Acquired Haemophilia: This is a rare, non-hereditary form where the body’s immune system creates autoantibodies that target and destroy its own clotting factors, often occurring in older adults or during pregnancy.

What is the current state of research into the etiology of Haemophilia?

Medical researchers continue to study the underlying mechanisms of Haemophilia to develop more effective therapies. Current research is heavily focused on gene therapy, which aims to introduce a functional copy of the F8 or F9 gene into the patient's cells to "fix" the root cause of the disorder. Scientists are also investigating why some patients develop inhibitors while others do not, exploring the complex interplay between genetics, the immune system, and environmental exposures to better tailor treatment plans for every person living with Haemophilia.

Next steps

• Consult a hematologist specializing in coagulation disorders to review your specific genetic profile or family history.


• Consider genetic counseling if you are planning a family to understand the inheritance patterns of Haemophilia.


• Join the DiseaseMaps.org community to connect with other families and share experiences regarding diagnosis and long-term management.


• Monitor for clinical trials through the NIH or local hemophilia treatment centers (HTCs) to stay informed on the latest gene therapy advancements.

Medical disclaimer: This information is for educational purposes only and should not replace professional medical advice, diagnosis, or treatment; always seek the guidance of your physician with any questions regarding a medical condition.

References

• World Federation of Hemophilia (WFH) - Guidelines for the Management of Hemophilia.


• NIH Genetic and Rare Diseases Information Center (GARD) - Haemophilia A and B overviews.


• Orphanet - Rare disease database for Hemophilia A (ORPHA:399) and Hemophilia B (ORPHA:400).


• OMIM (Online Mendelian Inheritance in Man) - Detailed genetic mapping for the F8 and F9 genes.