Bone Marrow Failure Disorders

At the ISTH 2021 Congress, held virtually from July 17–21, investigators from Johns Hopkins University reported results of their study (abstract PB1242) comparing the risk of recurrent thromboembolism in patients with PNH on C5 inhibition therapy who did or did not receive anticoagulation treatment. They reviewed the electronic medical records of patients at Johns Hopkins Hospital between January 2005 and October 2020 with documented PNH clones treated with eculizumab or ravulizumab longer than 6 months, selecting patients with a history of thromboembolism as determined by imaging or based on high clinical suspicion. Of 21 patients who had a history of thromboembolism, 11 discontinued anticoagulation, 6 never received or could not tolerate anticoagulation, and 4 continued anticoagulation after initiation of C5 inhibition. The thrombosis rate was 26.3 events/100 patient-years prior to C5 inhibition, 1.5 events/100 patient-years with anti-C5 monotherapy (P < .001), and 5.4 events/100 patient-years on combined anticoagulation and C5 inhibition (P = .016). Thrombosis rates between the anti-C5 monotherapy group and anti-C5 plus anticoagulation group were not significantly different (P = .4). Given these findings, the investigators concluded that “[d]iscontinuation of anticoagulation for secondary prevention of thromboembolism in PNH patients well-controlled on terminal complement inhibition appears safe.”