Unexpected test results in a patient with multiple myeloma.

Abstract

A 53-year-old male patient with an established diagnosis of IgG λ multiple myeloma was seen by a hematologist–oncologist in consultation from an outside hospital. He had previously received 1 cycle of chemotherapy treatment, but he was found to be intermittently noncompliant with his therapy. The patient reported occasional nosebleeds and fatigue. Except for a slightly cachectic appearance, the physical examination was unremarkable. Laboratory results are shown in Table 1. View this table: Table 1. Chemistry and hematology laboratory results. Serum protein electrophoresis revealed monoclonal paraproteinemia in high abundance marked by an intense band in the γ region. Immunofixation electrophoresis was not ordered at that time, but it was previously performed at another institution and was positive for IgG monoclonal protein. The attending pathologist noted the discrepancy between the presence of a monoclonal band by serum protein electrophoresis and the patient's quantitative immunoglobulin measurements. Several additional suspicious test results were also noted. Multiple myeloma is a hematologic malignancy characterized by proliferation of a neoplastic plasma cell population that usually leads to abundant production of a monoclonal immunoglobulin, also called paraprotein or M-protein, as well as decreased concentrations of normal polyclonal immunoglobulins. Overwhelming expansion of plasma cells in the bone marrow with concomitant suppression of other normal blood cell lineages often results in thrombocytopenia and anemia, which are classically manifested as symptoms of bleeding and fatigue. Renal insufficiency, as evidenced by increased blood creatinine and blood urea nitrogen concentrations, also may occur and is likely due to filtration of associated monoclonal free light chains, which can cause tubular damage. Serum protein electrophoresis typically yields a discrete band in the γ region, and immunofixation demonstrates the presence of IgG monoclonal protein in over 50% of cases (1). ### QUESTIONS TO CONSIDER 1. What are some expected laboratory results in a patient with multiple myeloma? 2. Which of the patient's laboratory test results are unexpected given his diagnosis …