Is Haemophilia hereditary?

Haemophilia is a hereditary genetic disorder, meaning it is passed from parents to children through specific gene mutations located on the X chromosome. Because it follows an X-linked recessive inheritance pattern, it most commonly affects males, though females can be carriers who may also experience mild symptoms.

Is Haemophilia considered hereditary or genetic?

Haemophilia is both a genetic and a hereditary condition. It is "genetic" because it is caused by permanent changes (mutations) in the DNA sequences of genes responsible for producing clotting factors. It is "hereditary" because these mutations are passed down from parents to their biological children through the germline. In the context of Haemophilia, the mutations occur on the F8 gene (for Haemophilia A) or the F9 gene (for Haemophilia B), both of which are located on the X chromosome.

What is the inheritance pattern of Haemophilia?

Haemophilia follows an X-linked recessive inheritance pattern. Since males (XY) have only one X chromosome, a single mutation in their clotting factor gene will result in the disease. Females (XX) have two X chromosomes; if they inherit one mutated gene, they are typically "carriers" who usually have enough normal clotting factor to avoid severe symptoms, though they may experience mild bleeding issues. For a child of a carrier mother and an unaffected father, the risk profile is as follows:

• For sons: A 50% chance of inheriting the mutated gene and having Haemophilia.


• For daughters: A 50% chance of inheriting the mutated gene and becoming a carrier.

Are de novo (spontaneous) mutations common in Haemophilia?

While Haemophilia is typically inherited, it is not uncommon for it to appear in families with no prior history of the condition. Approximately 30% of new Haemophilia cases are the result of a de novo or spontaneous mutation. This means the genetic change occurs for the first time in the affected individual, rather than being inherited from the parents. Even in these cases, once the mutation is present, it can be passed on to future generations.

What is the role of genetic testing and counseling?

Genetic testing is highly recommended for families affected by Haemophilia to identify the specific mutation within the F8 or F9 gene. This information is vital for accurate diagnosis and for identifying female carriers in the family. Genetic counseling provides families with a clear understanding of inheritance risks, especially when planning pregnancies. Options for those at risk include:

• Carrier testing: Blood tests to check clotting factor levels or genetic analysis to identify the mutation.


• Prenatal diagnosis: Procedures like chorionic villus sampling (CVS) or amniocentesis can detect the condition in a fetus.


• Preimplantation Genetic Testing (PGT): Used in conjunction with IVF to select embryos that do not carry the Haemophilia mutation.

Next steps

• Schedule a consultation with a clinical geneticist to discuss your family history and potential carrier status.


• Connect with the 334 members of the Haemophilia community on DiseaseMaps.org to share experiences and find emotional support.


• Contact your local haemophilia treatment center (HTC) for specialized care and access to genetic counseling resources.


• Review your family tree with a genetic counselor to map potential inheritance patterns before family planning.

Medical disclaimer: This information is for educational purposes only and should not replace professional medical advice, diagnosis, or treatment from a qualified healthcare provider.

References

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


• Orphanet: Haemophilia A (ORPHA:399) and Haemophilia B (ORPHA:400).


• World Federation of Hemophilia (WFH): Genetics of Hemophilia.


• OMIM (Online Mendelian Inheritance in Man): Hemophilia A (#306700) and Hemophilia B (#306900).