Researchers found that half of adolescents and adults with nonsevere hemophilia had experienced at least 1 bleed in the past, and that baseline factor (FVIII)/IX levels were inversely associated with the rate of joint bleeds, as published in Blood Advances.

“In this international multicenter study among people with non‐severe hemophilia A and B the age at diagnosis, the first bleed and the first joint bleed occurred at a later age in mild hemophilia compared to moderate hemophilia,” the authors wrote.

“Overall low bleeding rates were observed. The bleeding rates decreased with increasing baseline FVIII/IX levels, yet the bleeding rates varied considerably within similar baseline FVIII/IX levels.”

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A total of 304 male patients from 12 to 55 years of age with nonsevere hemophilia A and B from the DYNAMO study, an international multicenter study performed in hemophilia treatment centers were included. The outcomes assessed were characteristics reflective of bleeding phenotypes, such as age at diagnosis, age at first joint bleed requiring factor concentrate, and annual bleeding rates requiring treatment.

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In general, low bleeding rates were observed in this patient cohort, and the rates decreased with increasing baseline factor concentrate levels. Interestingly, the bleeding rates varied significantly even within similar levels of baseline FVIII/IX.

Given that even those with low bleeding rates can still develop joint disorders, the authors recommend patient education of those with nonsevere hemophilia on how to prevent and recognize joint bleeds. Patients with a moderate bleeding phenotype should discuss the possibility of prophylaxis with their health care provider.


Kloosertman FR, Zwagemaker AF, Bago C, et al. The bleeding phenotype in people with non-severe hemophilia. Blood Adv. Published online May 11, 2022. doi:10.1182/bloodadvances.2022007620