This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Haematology, Subject name: Pathology
A 9 year old boy with elevation in both PT and A PTT. What is the diagnosis? - 
Select and explain. 
A. Defect in extrinsic pathway, B. Defect in intrinsic pathway, C. Platelet function defect, D. Defect in common pathway
D: Defect in common pathway
Answer: D: Defect in common pathway 
Explanation: APTT is used to measure the intrinsic system factors as well as factors common to both intrinsic and extrinsic system. PT measures extrinsic system factor as well as factors in common pathway. As both are affected defect is in common pathway. Reference : Harsh Mohan textbook of pathology, 7th edition.Pg no.307,308