Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is associated with thrombotic complications in adults, but the incidence of COVID-19 related thrombosis in children and adolescents is unclear. Most children with acute COVID-19 have mild disease, but coagulopathy has been associated with multisystem inflammatory syndrome in children (MIS-C), a post-infectious complication. We conducted a multicenter retrospective cohort study to determine the incidence of thrombosis in children hospitalized with COVID-19 or MIS-C and to evaluate associated risk factors. We classified patients into one of three groups for analysis: COVID-19, MIS-C, or asymptomatic SARS-CoV-2. Among a total of 853 admissions (426 COVID-19, 138 MIS-C, and 289 asymptomatic SARS-CoV-2) in 814 patients, there were 20 patients with thrombotic events (TE) (including 1 stroke). Patients with MIS-C had the highest incidence (6.5%, 9/138) versus COVID-19 (2.1%, 9/426) or asymptomatic SARS-CoV-2 (0.7%, 2/289). In patients with COVID-19 or MIS-C, the majority of thrombotic events (89%) occurred in patients ≥12 years. Patients > 12 years with MIS-C had the highest rate of thrombosis at 19% (9/48). Notably, 71% of TE that were not present on admission occurred despite thromboprophylaxis. Multivariable analysis identified the following as significantly associated with thrombosis: age ≥12 years, cancer, presence of a central venous catheter, and MIS-C. In patients with COVID-19 or MIS-C, hospital mortality was 2.3% (13/564), but was 28% (5/18) in patients with thrombotic events. Our findings may help inform pediatric thromboprophylaxis strategies.

Introduction: Emicizumab is a recombinant humanized bispecific antibody that bridges factor IXa and factor X to mimic the cofactor function of factor VIII. It is approved to prevent bleeding in patients with haemophilia A (HA). Outside of clinical trials, there is limited data on outcomes of patients treated with emicizumab, particularly in children without inhibitors. Aim: To report our experience treating patients with emicizumab, including (a) bleeding rates pre and postemicizumab, (b) peri-procedural management and outcomes and (c) serious drug-related adverse events. Methods: Multicentre observational study in patients with HA who started emicizumab prior to 15 May 2019. Data collection continued until 15 October 2019 and included demographics, disease history, bleeding events, invasive procedures, thrombotic events and death. Annualized bleeding rates (ABR) prior to emicizumab were compared to postemicizumab. Results: Ninety-three patients (including three females) met inclusion criteria, 19 with an active inhibitor. Median age was 8.6 years; patients <12 years without inhibitors (n = 49) accounted for the majority. ABR dropped from 4.4 (inhibitors) and 1.6 (non-inhibitors) to 0.4 (both groups) on emicizumab, P = .0012 and .0025, respectively. There were 28 minor (21 port removals) and two major procedures. Three patients received 1-2 doses of unplanned factor postoperatively to treat minor bleeding events. No patient discontinued therapy, and there were no thrombotic events or deaths.