<prompt> In von Willebrands disease there is:Isolated prolonged PTT with normal PTNormal PTT with normal PTProlongation of both PT and PTTProlongation of thrombin time  <response>: Von Willebrand disease VWD - - Autosomal dominant disorder - The main source of plasma von-Willebrand factor is endothelial cells. - vWF circulates in the plasma in association with factor VIII. - Patients with VWD have defects in platelet function despite a normal platelet count - Deficiency of von willebrand factor VWF -promote platelet adherence and activation causes platelet adhesion BT and Intrinsic pathway activity aPTT . - von willebrand factor can also be found in : Platelet granules Subendothelium Endothelial cells within cytoplasmic vesicles called Weibel-Palade bodies CF Spontaneous mucosal bleeding - Petechiae purpura epistaxis melena excessive bleeding from wounds menorrhagia Lab findings - Platelet count - Normal Prothrombin time - Normal Bleeding time - Increased Activated paial thromboplastin time aPTT-Increased Rx - Desmopressin for mild form - Cryoprecipitate for severe form 