Development and desensitization therapy of high-response factor VIII inhibitors with severe allergic reaction in a moderate hemophilia A patient

Neutralizing antibodies (inhibitors) against factor VIII/IX (FVIII/FIX) poses a serious and challenging complication in the hemophilia treatment. Allergic reaction is more common in hemophilia B and always companion with FIX inhibitors, but it is rare in hemophilia A (HA). So far only few cases demonstrated FVIII-specific allergic response in hemophilia A. Coexistence of allergic reactions with inhibitors was contraindicated for immune tolerance induction (ITI) regimen which is the only proven therapy to eliminate inhibitor. We report a rare case of a 11-year-old boy with moderate HA who developed high titer inhibitor and severe allergic reaction to both plasma derived and recombinant FVIII concentrates. Inhibitor was eliminated with the use of prednisone. Further desensitization protocol by administering rFVIII of increasing does from 0.01 IU/kg to 40 IU/kg with a pre-determined time schedule allowed patient tolerance to the normal dose and infusion time to FVIII.