[Factor IX inhibitor in hemophilia B presented with anaphylactoid symptoms: report of 3 cases].

Three patient with hemophilia B who developed anti-factor IX antibodies were reported. All 3 had allergic and/or anaphylactoid symptoms when the antibodies were found. The antibodies were noted between 4 and 17 days after exposure to factor IX. It was suggested that the anaphylactoid symptoms were closely related to the occurrence of anti-factor IX antibodies.