This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
A 13-year old girl with Menorrhagia having Von Willebrands disease will show : 
Select and explain. 
A. Isolated prolonged PT with a normal PTT, B. Prolongation of both PT and PTT, C. Prolongation of thrombin time, D. Isolated prolonged PTT with a normal PT
D: Isolated prolonged PTT with a normal PT
Answer: D: Isolated prolonged PTT with a normal PT 
Explanation: Von Willebrand's factor acts as a plasma carrier of factor VIII and circulates in the blood as factor VIII-VWF complex. Its deficiency therefore impairs the intrinsic pathway of coagulation and prolongs the GPTT as the intrinsic pathway of coagulation. Ref:Kligman, Behrman, Jenson, Stanton (2008), Chapter 477, "VON WILLEBRAND DISEASE", In the book, "Nelson's Textbook of Pediatrics", Volume 2, 18th Edition, New Delhi, Page 2073