A 64 year old women without any previous history of bleeding diathesis presented with bone pain and gastrointestinal bleeding. An isolated severe factor X deficiency (factor X activity 0.5%, factor X antigen less than 12.5%) was found. No inhibitor that inactivated factor X in vitro or interfered with factor X assay could be demonstrated. Substitution therapy with a prothrombin complex preparation containing factor X (PPSB Biotest) was given. Factor X recovery in the first 2 days was lower than expected (below 20%) and half life of factor X was shortened (150 minutes). Subsequently, a diagnosis of multiple myeloma (light chain myeloma, type kappa) was made. Amyloidosis was excluded by electronmicroscopic examination of rectum biopsies. Chemotherapy according to the M2 protocol (Case et al) was initiated. Factor X recovery improved dramatically within 2 weeks and there was a continuous increase of factor X activity and antigen during chemotherapy. After 6 courses a complete haematological remission (less than 5% plasma cells in the bone marrow, disappearance of light chains) was obtained and factor X activity and antigen returned to normal.Isolated factor X deficiency is a wellknown complication of amyloidosis. To our knowledge, this is the first case of factor X deficiency in multiple myeloma without amyloidosis. The complete normalization of factor X after successful chemotherapy indicates that plasma cell proliferation may have been the cause of the factor X deficiency. Binding of factor X to plasma cells containing light chains could be a possible explanation, and we are currently examining this hypothesis.
A Case Report of Acquired Factor X Deficiency in a Patient With Multiple Myeloma