Genetics: Family History or Spontaneous Variant
Hemophilia is a genetic disease. It occurs when there is a change within the gene that makes factor VIII or factor IX. This gene contains the instructions your body uses to make certain blood clotting factors. For people with hemophilia diagnosis, these clotting factors aren't made in sufficient quantities, if at all.
In approximately 70% of cases, there is a known family history of hemophilia. In the other 30%, there may be no family history of hemophilia, or it may not be apparent. For these patients, hemophilia is often caused by a spontaneous variant.
Learn more about Inheritance Patterns