LAUSR

Abstract Emicizumab has been widely used for prophylaxis in patients with hemophilia A (HA) of all ages, with or without factor VIII inhibitors. Data on emicizumab efficacy are certainly significant; however, protection against bleeding is not absolute, and the breakthrough bleeding risk can be approximately equivalent to that of patients with mild HA. This single-center retrospective review aimed to present the rate and management of breakthrough bleeding events in pediatric HA patients with and without inhibitors who are on emicizumab prophylaxis. Fifty-one pediatric patients on emicizumab prophylaxis that were followed up at Birmingham Children’s Hospital between March 1, 2018, and May 15, 2021, were included in the current study. Our results showed that 56.8% (29/51) experienced no bleeding events, and 80.3% (41/51) had no major treated bleeds during the follow-up period. A total of 29.4% (15/51) had minor bleeds that resolved spontaneously or with antifibrinolytics. Overall, 19.6% (10/51) of the patients received additional FVIII to prevent or treat breakthrough bleeding. One patient had a major bleeding event in the form of hematuria. However, it resolved without treatment. Both major and minor bleeding episodes occurred in 7.8% (4/51) of patients. None of the patients with inhibitors (5/51) developed breakthrough bleeding. Only a few, mostly minor, breakthrough bleeding episodes were reported in our cohort. The balance between bleeding control and the risk of inhibitor development after episodic factor administration should be considered. Therefore, careful decisions should be made in managing bleeding events. Supplemental data for this article is available online at