Successful Treatment of Life-threatening Bleeding Caused by Acquired Factor X Deficiency Associated with Respiratory Infection.

Acquired factor X deficiency (AFXD) is a very rare coagulation disorder. A 40-year-old man with no comorbidities suffering from a fever, malaise, and severe hemorrhagic symptoms, including massive hematuria, was emergently admitted. His platelet count was normal, but his prothrombin time and activated partial thromboplastin time were markedly prolonged, which was thought to be due to autoantibody against a coagulation factor in the common pathway. Despite severe massive hematuria resulting in transient renal failure, he was successfully treated with urgent immunosuppressive therapy. Computed tomography revealed bronchopneumonia, which improved with antibiotic administration. AFXD without evidence of amyloidosis was subsequently diagnosed.