Anaphylactic Reaction After Replacement Therapy In Haemophilia B Patient with Inhibitor to Factor IX

Abstract 4662

Replacement therapy is a very hard challenge in haemophilia B with inhibitor. We describe the case of a child with severe haemophilia B and with a family history positive for development of inhibitor to factor IX (FIX) and for occurrence of allergic reaction after replacement therapy. Genetic analysis demonstrated an almost complete deletion of FIX gene. The child received replacement therapy first in his life when he was 5 years old because of the occurrence of a large haematoma of the left thigh. He was treated with recombinant FIX concentrate at the dosage of 30 IU/kg daily for three days and no inhibitor to FIX was evidenced after this therapy. Two months later the patient was treated with a single dose of recombinant FIX concentrate at the same dosage for the occurrence of a post-traumatic joint bleeding of the right knee. An inhibitor towards FIX (1.7 B.U.) was detected two weeks after this treatment and confirmed in a subsequent analysis performed after ten days (1.4 B.U.). One month later the patient was hospitalized for a post traumatic hemarthrosis of the right shoulder. In this occasion it was planned to treat the patient with recombinant FIX under careful monitoring in intensive care unit considering of the inhibitor. After the slow endovenous infusion of 200 IU of recombinant FIX concentrate we stopped immediately the administration because the child presented cough, mild respiratory failure, tachycardia, tongue and lips oedema, lips cyanosis, diffuse vasodilatation, psychomotor agitation. He received also hydrocortisone, antihistaminic by intramuscular injection and oxygen by facial mask. The presence of inhibitor towards FIX and anaphylactic reaction occurrence preclude forever any replacement therapy with FIX both recombinant and plasmatic (PCC and/or aPCC). After this episode the patient needed another hospitalization for a tonsil bleeding with severe anaemization. We treat him with recombinant activated FVII (rFVIIa) first at the dosage of 270 mcg/kg in bolus, and after at the dosage of 90 mcg/kg every three hours for one day with complete bleeding remission. We encourage the careful monitoring of inhibitor towards FIX in haemophilic B patients especially with large FIX gene deletion. It could prevent severe anaphylactic reaction during replacement therapy. Considering the previous anaphylactic reaction, in this child rFVIIa represents the only therapeutic option for bleeding management.