A patient has normal PT and Platelet Count. The aPTT is increased and factor VIII levels are observed to be 60 lukIL (60%). There is no associated history of bleeding even after a surgical procedure. The most likely diagnosis is:
Factor IX deficiency
Factor VIII inhibitors
Lupus anticoagulant
Thalassemia
Answer is C (Lupus Anticoagulant) Isolated prolongation of aPTT with no clinical history of bleeding suggests the presence of Lupus anticoagulant or deficiency of contact factors (Factor XII, Prekallikrein or HMWK)