A 6-year-old boy presents with recurrent epistaxis and easy bruising since infancy. Vital signs: BP 105/68, HR 98, RR 22, Temp 37°C, SpO2 98%. Laboratory studies reveal platelet count 140,000/μL, prolonged bleeding time at 12 minutes, and peripheral smear showing giant platelets. Platelet aggregation studies fail to improve with ristocetin despite normal von Willebrand factor level. He denies recent infections or medication use. Which of the following represents the most likely underlying defect?

1. A)Deficient GpIIb/IIIa causing impaired platelet aggregation
2. B)Absent ADAMTS13 causing large vWF multimers
3. C)Autoantibodies against platelets causing splenic destruction
4. D)Deficient GpIb causing impaired platelet adhesion to von Willebrand factorGABARITO
5. E)Deficient factor VIII causing impaired intrinsic coagulation