Key Takeaways

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.