一位1 歲男童因最近時常瘀青來就診,病童檢驗報告如下WBC:8,700/\mathrm{mm}^{3}、Hgb:12 gm/dL、PLT:320,000/\mathrm{mm}^{3}、prothrombin time(PT):11.7/10.8(patient/control)秒、activated partial thromboplastin time(aPTT):89.3/29.6(patient/control)秒、bleeding time(Ivy’s method):1.5 min、von Willebrand factor(vWF)antigen 72%,此病童最有可能是: