Immune tolerance induction in a severe hemophilia B child with low titer inhibitors

Hemophilia B is an X-linked inherited bleeding disorder caused by either the absence or reduced biosynthesis of clotting factor IX (FIX). This disorder affects approximately 1 in 30,000 male individuals worldwide. Patients with severe form (FIX <1%) account for 30%-45% of hemophilia B cases and usually report of spontaneous bleeds. Treatment includes FIX replacement prophylactically to prevent complications. However, the patient may develop inhibitors against FIX, which is rare and a serious complication, reported to occur in 1.5%-3% of hemophilia B patients. Immune tolerance induction is a therapeutic strategy to eliminate inhibitors. We report a 14-month-old-male child with severe hemophilia B on primary prophylaxis, presented with right knee swelling. He developed anaphylactic reaction while receiving recombinant FIX concentrate. Investigation revealed that FIX inhibitor titers were 1.0 Bethesda Units. He was managed with immune tolerance induction successfully.