IgG Monoclonal Immunoglobulin (M-protein) as Factor V Inhibitor in Multiple Myeloma Patient: Case Report and Discussion

Abstract

We present a case of a 53-year-old male with a symptomatic relapse of IgGλ multiple myeloma who was readmitted to the hospital with clinical symptoms of retroperitoneal hematoma. Laboratory tests revealed high concentration of monoclonal immunoglobulin G (32 g/l, 91.6% of total IgG) in the serum, prolongation of activated partial thromboplastin time (aPTT), prothrombin time (PT), and thrombin time (TT), significantly decreased factor V procoagulant activity and the presence of factor V inhibitor. After successful retreatment with the use of six cycles of bortezomib, adriamycin and dexamethasone, the monoclonal IgG concentration in the patient's serum significantly decreased (up to 1.3 g/l). At that time, also the normalization of the results of aPTT, PT and TT was stated. Therefore, the presence of factor V inhibitor in monoclonal immunoglobulin fraction was suspected. To confirm this, the monoclonal immunoglobulin G from the patient's initial blood sample was isolated, a series of dilutions of it in standard human plasma was prepared and the activity of factor II, factor V and aPTT, PT and TT in the prepared plasma samples were measured. The results of ex vivo studies matched those obtained in vivo, proving that the monoclonal immunoglobulin G produced by multiple myeloma cells acted as a factor V inhibitor.