[PERIOPERATIVE MANAGEMENT OF AN ADOLESCENT GIRL WITH SEVERE FACTOR XI DEFICIENCY AND INHIBITORS].

INTRODUCTION: Factor XI (FXI) deficiency is an autosomal bleeding disorder characterized by injury-related hemorrhage, mostly associated with surgical procedures at sites noted for high fibrinolytic activity. Severe FXI deficiency is defined when the FXI level is lower than 15-20 IU/dL. Perioperative prophylactic treatment for high-bleeding-risk surgery in patients with severe FXI deficiency is based on fresh frozen plasma (FFP) transfusions or FXI concentrate (where available). Exposure to FFP and to FXI concentrate may lead to the development of inhibitory antibodies against FXI. This phenomenon occurs mostly in patients with very severe FXI deficiency (baseline FXI <1IU/dL) and is associated with an increased risk of substantial perioperative bleeding, unresponsive to FXI replacement. Thus, in individuals with severe FXI deficiency, routine testing for the presence of inhibitory antibodies against FXI is recommended. We present a 17-year-old adolescent patient with very severe FXI deficiency, who developed an inhibitor to FXI following FFP exposure associated with neurosurgery for medulloblastoma. Prophylactic treatment for subsequent invasive procedures consisted of single low dose (10 mcg/kg) recombinant activated factor VII (rFVIIa) and tranexamic acid (Hexakapron). The procedures were performed uneventfully, with no hemorrhagic or thrombotic complications. In patients with very severe FXI deficiency, the development of inhibitory antibodies following plasma replacement therapy comprises a rare and challenging occurrence. The formulation of a safe and effective evidence-based protocol for hemostatic support in these patients requires multi-center collaboration.

Pediatric severe factor XI deficiency: A multicenter study.

BACKGROUND: Factor XI (FXI) deficiency is a rare autosomal recessive bleeding disorder. Only scarce publications address its clinical features in children. The increased prevalence of FXI deficiency in Israel enabled data collection for this large multicenter cohort study. OBJECTIVE: Some hemostatic challenges may be unique or more common in children, such as bleeding in the neonatal period or trauma-related injury. The current study was designed to explore the potential impact of these differences in children with severe FXI deficiency. METHODS: Medical files of all children with FXI level under 15% followed at five tertiary centers were evaluated. The retrieved data comprised demographic and clinical characteristics, including bleeding episodes, surgical interventions, treatment strategies, as well as laboratory features. RESULTS: Sixty children, whose median age at diagnosis was 4.2 years and their median FXI level was 4%, were included. Three children experienced triggered intracranial hemorrhage (ICH) and two children had major bleeds. No bleeding complications occurred in surgeries in which hemostatic treatment consisting mostly of tranexamic acid or fresh frozen plasma was applied (n = 45). In contrast, excessive bleeding was noted in 25% of surgical procedures performed without hemostatic preparation (p = .002). CONCLUSION: This study's findings confirm the generally favorable outcome of this rare bleeding disorder, with no spontaneous bleeds or cases of perinatal ICH. Nonetheless, proper diagnosis and adequate hemostasis in the surgical setting are imperative. Unlike previous studies in adults, our pediatric study suggests an association between the severity of FXI deficiency and bleeding tendency.