Almost 1 in 5 mild hemophilia patients are female, according to a study published in Haemophilia. This finding indicates the need for specialized care based on the levels of clotting factors and history in female patients affected by the disease.

Female patients may have the same levels of factor VIII or factor IX as male patients affected by hemophilia. To estimate how many female patients are receiving care at hemophilia treatment centers in the United States and compare their characteristics with male patients with the disease, a team of researchers led by Christopher J. Bean, PhD, collected data at a hemophilia treatment center from January 2012 to September 2020. They evaluated patients with hemophilia A and B by sex for clinical and demographic characteristics.

They found that almost all (97.8%) male patients with the disease had clotting factor levels lower than 40%, whereas less than half of female patients (47.6%) attending the center had factor levels lower than 40%. Of patients who had severe hemophilia, 0.48% were female. Of those who had moderate disease, 1.4% were female, and of those with mild hemophilia, 17.9% were female.

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Female patients with the disease were older, more often white, and less often non-Hispanic than male patients. They were also less likely to have a history of human immunodeficiency virus (HIV) or hepatitis C infection. However, they were twice as likely to have an unknown infection status. Finally, female patients with mild hemophilia more often had no health insurance than male patients with the disease.  

The researchers concluded, “Designation of women and girls with low factor activity levels as having hemophilia like their male counterparts rather than as carriers, which has been the practice historically, would help them to receive appropriate treatment and reimbursement for care.” They added that this may “decrease their reported negative experiences with the health care system.”

Hemophilia A and B are both caused by a mutation in a gene located on the X chromosome, so they mainly affect male patients. However, some female individuals with the mutation can also have symptoms that, in some rare cases, are severe.


Miller CH, Soucie JM, Byams VR, et al. Women and girls with haemophilia receiving care at specialized haemophilia treatment centres in the United States. Haemophilia. Published online September 4, 2021. doi:10.1111/hae.14403