✅ An elevated PT and aPTT indicate a deficiency of or inhibitor against a clotting factor in the common pathway (factor X [FX] or factor V [FV]) or combined deficiencies/inhibitors in the intrinsic and extrinsic pathways.
✅ Correction of a prolonged PT and aPTT with normal plasma (mixing study) normally suggests a deficiency in a clotting factor(s) rather than an inhibitor.
✅ Acquired FX deficiency is most often associated with systemic AL amyloidosis, a hematological disorder characterized by a monoclonal gammopathy leading to misfolding and tissue deposition of immunoglobulin light chain proteins. Deposited amyloid fibrils adsorb FX from the circulation, leading to a reduction in FX half-life and subsequently FX levels.
✅ There is a FX concentrate that can be used in patients who have FX deficiency and are bleeding. If the product is not available, the treatment of choice is prothrombin complex concentrates (PCC).
✅ Other treatment for acquired FX deficiency include eradication of inhibitor if present and treatment of underlying medical condition, e.g. amyloidosis.