Use of oral anti-Xa inhibitor in prosthetic mechanical aortic valve with warfarin hypersensitivity due to the FIX p.(Ala37Thr) pro peptide variant: case report and literature review.

Bleeding is the most common side effect during treatment with vitamin K antagonists (VKAs). Sometimes, VKA use causes bleeding episodes due to rare variants in the factor IX (FIX) pro peptide that modify the affinity of FIX pro peptide to the binding of γ-glutamyl carboxylase. We report on a 51-year-old patient who presented with recurrent spontaneous and severe intramuscular and cutaneous bleedings during VKA (warfarin) treatment for the presence of prosthetic mechanical aortic valve.