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MBBS QUESTION #10226
Question 1
Hemophilia A results from deficiency of which clotting factor, producing an isolated prolongation of the activated partial thromboplastin time (aPTT) with a normal prothrombin time (PT)?
  • Factor VII
  • Factor VIII✔️
  • Factor IX
  • Factor XI
Correct Answer Explanation
Factor VIII deficiency (Hemophilia A) selectively prolongs the aPTT (intrinsic pathway) while the PT (extrinsic pathway, factor VII-dependent) remains normal. Factor IX deficiency causes the clinically similar Hemophilia B, with an identical aPTT/PT pattern, distinguished only by specific factor assays.