D2.345 - Successful Desensitization in a Pediatric Patient Who Developed an Immediate-Type Systemic Hypersensitivity Reaction to FVIII/vWF Concentrate

Successful Desensitization in a Pediatric Patient Who Developed an Immediate-Type Systemic Hypersensitivity Reaction to FVIII/vWF Concentrate

Introduction: Systemic hypersensitivity reactions may occur in response to plasma-derived vWF/FVIII replacement products used in the treatment of von Willebrand disease (vWD). Although these reactions are commonly attributed to non-IgE-mediated mechanisms such as immune complex formation or complement activation, recent evidence suggests that IgE-mediated pathways may also be involved.

Case Presentation: A 10-year-old girl with vWD had been receiving prophylactic vWF/FVIII (Haemate-P®) replacement therapy for five years without prior adverse reactions. In January 2026, she developed generalized urticaria and severe abdominal pain at the 10th minute of infusion. She was diagnosed with anaphylaxis and treated with 0.01 mg/kg intramuscular epinephrine, with rapid symptom resolution. Skin prick (1:1) and intradermal (1:10) testing with Haemate-P® were negative. As no alternative therapy was available, factor VIII inhibitor levels were negative, and treatment was life-saving, desensitization was planned. Following corticosteroid and antihistamine premedication, a three-solution (1/100, 1/10, 1/1) 12-step desensitization protocol was initiated. During step 10 (Solution III at 20 mL/hour), facial urticaria developed. The infusion was stopped and symptomatic treatment was administered. After complete resolution within 30 minutes, the protocol was resumed from step 9, and the target dose of 350 IU was successfully completed. No reactions were observed during the 2-hour post-procedure observation period.

Conclusion: Desensitization appears to be a safe and effective strategy for managing immediate-type systemic hypersensitivity reactions to plasma-derived factor concentrates. In hematologic conditions such as vWF deficiency, where therapy is life-saving and alternative options are unavailable, desensitization may represent a critical therapeutic approach.

Keywords:von Willebrand disease, desensitization, anaphylaxis, hypersensitivity reaction, pediatric