Background: Emicizumab, a subcutaneously administrated bispecific monoclonal antibody that bridges activated factor IX and factor X, was recently approved for the prophylactic treatment of patients with hemophilia A following demonstration of a reduced rate of bleeding events and improvement of health-related quality of life.

Aims: Describe the use of Emicizumab in a pediatric female with severe hemophilia A.

Methods: Here we report Emicizumab therapy in a 6-year-old female with severe haemophilia A, factor VIII activity < 1%, compound heterozygous (intron 22 inversion and missense variant c.6742T>C). The patient was initiated on intravenous prophylactic infusions (second generation standard half-life product) when 2 years-old after multiple soft tissue bleeds and epistaxis leading to iron deficiency anemia. Patient was eventually transitioned to prophylactic therapy with Emicizumab weekly due to persistence of multiple episodes of epistaxis, multiple emergency department (ED) visits for acute bleeding events, an annualized bleeding rate (ABR) higher than 10, poor adherence, and development of heamophilia target joint (3 or more joint bleeds in a period of 6 months) in her ankles (bilateral) and right knee.

Results: The patient received Emicizumab for approximately 2 years with abolition of joint bleeds, control of epistaxis, reduction of ABR to 2, and no ED visits. There was multimodal assessment using POCUS imaging and MRI and documented clinical improvement.

Conclusions: We believe this to be the first case describing a female with severe haemophilia A using Emicizumab, and the first pediatric patient with resolution of haemophilic arthropathy after 2 years on Emicizumab therapy. There is currently a lack of data supporting the safety of Emicizumab in female patients of reproductive age; but our experience suggests that Emicizumab may be considered in female patients before puberty, and particularly those with haemophilic arthropathy. Our experience highlights the need for further studies of Emicizumab.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/clinical-improvement-of-haemophilic-arthropathy-in-a-female-pediatric-patient-with-severe-hemophilia-a-following-treatment-with-emicizumab/