Intracranial hemorrhage in an infant leads to the diagnosis and treatment of severe hemophilia B: a case report

Hemophilia B is a rare bleeding disorder in males, characterized by a deficiency in coagulation factor IX (FIX). Replacement of FIX with a recombinant FIX (rFIX) fusion protein, to sustain therapeutic plasma levels, is recommended as both treatment and prophylaxis to prevent bleeding episodes, particularly intracranial hemorrhage (ICH).

This case report outlines the management of ICH in a 7-month-old infant with severe hemophilia B, following an accidental trauma-related event, resulting in a thin compound fracture of the left occiput. FIX levels were extremely low (˂1.0%) and large deletions of the coagulation F9 gene (including exons 1–6) were identified. Intensive treatment with a rFIX fusion protein conjugated to the immunoglobulin Fc fragment (rFIXFc) continued for 18 days before hospital discharge. A continuous regimen of weekly rFIXFc infusions was implemented. Thirty days after initiating rFIXFc therapy, neutralizing antibodies or FIX inhibitors (common in patients with large F9 gene deletions) were observed, causing a diffuse skin rash. Such allergic reactions typically indicate progression to potentially serious nephrotic syndrome. A unique immunotolerance regimen of oral oxatomide and intravenous hydrocortisone was started to proactively prevent allergic reactions in this patient during rFIXFc prophylaxis. Even though low titers of the inhibitor (0.6–1.0 Bethesda units) were observed occasionally during subsequent follow-up, there were no signs of further allergies or development of nephrotic syndrome.

This is an uncommon case in which rFIXFc was continued despite the appearance of an allergic reaction and the development of FIX inhibitors. Subsequent allergic reactions were prevented with a combination of oral oxatomide and intravenous hydrocortisone given prior to prophylactic rFIXFc. Further studies are recommended to determine the usefulness of this combination with rFIX therapy.