INDUCTION OF IMMUNE TOLERANCE IN A 7-YEAR-OLD HEMOPHILIAC WITH AN ANAPHYLACTOID INHIBITOR

Background: Anaphylactic reactions were a rare complication of low pur ity WT concentrates, but not with high purity VIII concentrates. Case: 7 y/o WM with severe hemophilia A, received only cryoprecipitate and monoclonally purified VIII concentrates; developed postinfusional urti caria. A 2-Bethesda-unit inhibitor was detected. Generalized urticaria and bronchospasm following factor developed as the titer increased. S kin tests demonstrated reactivity to plasma derived VIII, but not reco mbinant VIII (rhVIII). Attempts at desensitization using rhVIII failed . ELISA revealed an anti-VIII IgE antibody. He was treated with a modi fied tolerance regimen using rhVIII starting at 500 U/day with aggress ive premedication. The dosage increased by 200 U weekly as tolerated t o a maximum of 100 U/kg/d without symptoms. Results: His antibody tite r decreased rapidly once he started 100 U/kg/d. Six months later, the inhibitor was <1 Bethesda unit. Conclusion: Immune tolerance induction using a graduated dosage of rhVIII was successful.