Factor X Deficiency Caused by Nonsecretory Myeloma Successfully Corrected with Bortezomib: A Case Report and Review of the Literature. 
A 62-year-old female presenting with anemia and extensive hemorrhages is reported.  Coagulation tests showed significantly prolonged prothrombin time (PT) and activated partial thromboplastin time.  Decreased levels of clotting factor X activity were determined (5.4%).  Bone marrow biopsy revealed neoplastic plasma cells.  Serum and urine protein electrophoresis were both negative for monoclonal gammopathy, and both bone marrow and abdominal fat biopsies were negative for amyloid deposition.  The patient was diagnosed as suffering from nonsecretory multiple myeloma (MM) complicated by acquired factor X deficiency.  A complete response (CR) of the myeloma and recovery of factor X activity (56.6%) were achieved after the administration of treatment, including chemotherapy and bortezomib.  We suggest that patients with nonsecretory MM might present with factor X deficiency and should be carefully screened for light chain amyloidosis.  Novel agents such as bortezomib should be highly considered as treatment in these patients.