Hemophilia A (factor VIII deficiency) and Hemophilia B (factor IX deficiency) are rare inherited bleeding disorders, with different severities that mostly affects males. Severe hemophilia affects women too, although this is rare.

Let’s first explore the genetics of hemophilia and how it affects families regarding women with bleeding disorders. A female who inherits one affected X chromosome becomes a “carrier” of Hemophilia.  It is important to remember that Hemophilia affects families: If you are a man that has Hemophilia, all your daughters will be obligate carriers. If you are a woman (obligate or non-obligate carrier), you have a 50 /50 chance that your male children have Hemophilia and a 50/50 chance that your female children are carriers/mild Hemophiliacs. If you have a son with Hemophilia you have a similar chance to have a daughter with Mild Hemophilia, what used to be and sometimes still is called a symptomatic carrier. Similarly, there are chances that you might be affected and have low factor levels and bleeding symptoms yourself, and so have mild Hemophilia yourself. 

Carriers of Hemophilia might have bleeding disorders themselves and they are not aware of it, as they usually do not experience severe bleeding symptoms. Carrier level factor tends to have broad range. In her paper “Women and bleeding disorders: diagnostic challenges” Dr. Paula James introduced a proposal to the Women’s Issues in Thrombosis and Hemostasis ISTH Scientific and Standardization Committee, that hemophilia carrier with factor levels >5% to 40% should be referred to as a woman or girl with mild hemophilia. Carriers with factor levels >40% should be referred to as symptomatic or asymptomatic, depending on their bleeding phenotype. We will update you more on these possible recommendations for nomenclature for carriers once more data is available.