Background: Factor XI (FXI) deficiency is a rare bleeding disorder in which bleeding usually occurs only following surgery or trauma. To date no studies examining the presentation and complications of this disorder in the pediatric population have been conducted.

Aims: To evaluate the presentation, hemostatic phenotype and complications in a cohort of children aged 0-18 years diagnosed with severe FXI deficiency

Methods: After IRB approval, electronic medical records were screened to identify children with severe FXI deficiency (defined as a FXI level=15%, compatible with homozygous or compound heterozygous mutations), followed at our tertiary center. Data regarding reasons for referral, bleeding symptoms, surgeries outcome and complications were evaluated.

Results: Twenty-two children whose median age at diagnosis was 7 years (range: 1 day- 16 years) comprised the study cohort. In 68% evaluation was performed either due to family history or preoperatively.
Seven patients presented with bleeding symptoms: triggered intracranial hemorrhage (ICH; 2/7), excessive bleeding following trauma or post-surgical procedures and gastrointestinal bleeding. Another ICH was encountered during follow up. Only one child presented with major bleeding following teeth extraction.
Four Major surgeries were safely performed among children in our cohort assisted by plasma transfusions and tranexamic acid. Sixteen male patients underwent circumcision as neonates. Excessive bleeding post circumcision was noted in two patients, one bled despite the administration of prophylactic tranexamic acid.
Interestingly, 2 children sustained triggered thrombotic complications, both resolved without anticoagulant therapy.

Conclusions: This study describes the bleeding phenotype associated with severe FXI deficiency in a pediatric cohort. The significant incidence of ICH as well as the occurrence of thrombosis in children with severe FXI deficiency warrants attention and should be further evaluated in prospective larger cohorts.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/severe-fxi-deficiency-a-pediatric-cohort/