Key Takeaways

✅ An elevated activated partial thromboplastin time (aPTT) and normal prothrombin time (PT) suggests a deficiency of or inhibitor against one or more clotting factors in the intrinsic pathway.

✅ Correction of a prolonged aPTT with normal plasma (mixing study) suggests a deficiency in a clotting factor(s) rather than an inhibitor.

✅ Deficiency in factor VIII (FVIII) (as distinct from inhibitor against FVIII) may be congenital (hemophilia A or von Willebrand disease) or acquired (typically acquired von Willebrand syndrome [AVWS]).

✅ von Willebrand disease – whether congenital or acquired – is confirmed by demonstrating reduced von Willebrand factor (vWF) activity.

✅ vWF activity that is disproportionately low relative to reduction in vWF antigen suggests loss of high molecular weight vWF, as seen in von Willebrand disease, type 2 or AVWS.

✅ AVWS is almost always associated with an identifiable medical condition such as a plasma cell dyscrasia, cardiac condition, medication effect, or autoimmune disorder.

✅ Treatment of AVWS involves treating bleeding (using DDAVP and/or vWF/FVIII concentrates) and treating the underlying medical condition.