A 67-year-old man has had increasing weakness, fatigue, and weight loss over the past 5 months. He now has decreasing vision in both eyes and has headaches and dizziness. His hands are sensitive to cold. On physical examination, he has generalized lymphadenopathy and hepatosplenomegaly. Laboratory studies indicate a serum protein level of 15.5 g/dL and albumin concentration of 3.2 g/dL. A bone marrow biopsy is performed, and microscopic examination of the specimen shows infiltration by numerous small plasmacytoid lymphoid cells with Russell bodies in the cytoplasm. Which of the following additional laboratory findings is most likely to be reported for this patient?

Hyperviscosity syndrome includes visual disturbances, dizziness, headache, and Raynaud phenomena. His bone marrow is infiltrated with plasmacytoid lymphocytes that have stored immunoglobulins in their cytoplasm (Russell bodies). All of these findings are consistent with lymphoplasmacytic lymphoma (Waldenstrom macroglobulinemia). In this disorder, neoplastic B cells differentiate to IgM-producing cells; there is a monoclonal IgM spike in the serum. These IgM molecules aggregate and produce hyperviscosity, and some of them agglutinate at low temperatures and produce cold agglutinin disease. Myeloma, which is typically accompanied by a monoclonal gammopathy, most often does not cause liver and spleen enlargement, and morphologically, the cells resemble plasma cells. Light chains in urine (Bence Jones proteins) also are a feature of multiple myeloma. Hypercalcemia occurs with myeloma because myeloma cells produce MIP1-a that up-regulates RANKL production and increased osteoclastic activity, so punched-out lytic bone lesions are typical of multiple myeloma. A t (14;18) translocation is characteristic of a follicular lymphoma. There is typically no leukemic phase to Waldenstrom macroglobulinemia.