Prekallikrein deficiency is associated with which finding?

• A. Prolonged aPTT that does not correct with a mixing study
• B. Autosomal dominant inheritance
• C. Increased risk of thrombosis
• D. Delayed bleeding at the incision site following surgery

Answer: (C)

Prekallikrein deficiency alters the contact activation system of coagulation, which is part of the intrinsic pathway. In the lab, this deficiency can show up as a prolonged aPTT, but clinically these patients do not typically have a bleeding tendency. The notable and somewhat paradoxical clinical signal that has been reported in some individuals with this deficiency is an increased risk of thrombosis, rather than a tendency to bleed. That makes thrombotic risk the most fitting association among the options.

In terms of other choices, prekallikrein deficiency is not classically inherited in an autosomal dominant fashion (it’s generally considered autosomal recessive). Bleeding after surgery is not a typical feature. And mixing studies in true factor deficiencies or related contact-pathway deficiencies usually show correction, indicating the issue is a deficiency rather than an inhibitor; a non-correcting mixing result would suggest an inhibitor, which is not characteristic of prekallikrein deficiency.