An IgE multiple myeloma: contradictory findings in clinical laboratory testing.

Abstract BACKGROUND: IgE multiple myeloma is a rare kind of plasma cell disorder, characterized by an aggressive clinical course, where laboratory testing plays a fundamental role for the correct diagnosis in order to start a targeted therapy. In the present paper it is described a case of IgE myeloma where contradictory findings between immunometric and separative techniques were found. MATERIALS AND METHODS: Serum and 24h urine samples were tested using electrophoresis and immunofixation electrophoresis employing IgE antiserum and IgE were quantified using an immunometric method. RESULTS: Serum immunofixation evidenced a monoclonal band ascribable to IgE lambda and IgE serum concentration was 1,364,00 kU/L. Urine electrophoresis evidenced a band compatible with IgE, and urine concentration was 2715 kU/L. On the contrary in the immunofixation of the urine sample no band reacting with IgE antiserum was found. CONCLUSIONS: Considering that the immunometric method measured IgE in urine sample and the electrophoresis of urine sample evidenced a band compatible with IgE, the explanation could be that during renal filtration or because of some characteristics related to urine matrix, the immunoglobulin IgE could had been modified in the site recognized by the antiserum used in immunofixation, and not in the one used in the immunometric method.