A Rare Case of Waldenström Macroglobulinemia/Lymphoplasmacytic Lymphoma with Light Chain Discrepancy between B Lymphocyte Population and Serum Paraprotein.

Waldenström macroglobulinemia (WM) is a subset of lymphoplasmacytic lymphoma with bone marrow involvement, monotypic immunoglobulin (Ig) M and a light chain of neoplastic cells. A 68-year-old woman presented with fever, nausea, vomiting, and pancytopenia. Her serum albumin/globulin ratio was reversed, and monoclonal gammopathy of IgM, lambda type (23.20%, 1.58 g/dL) was detected. In her bone marrow, increased small lymphocytes were admixed with plasmacytoid lymphocytes and plasma cells. She was diagnosed as having lymphoplasmacytic variant of WM. Immunohistochemical stains and flow cytometic analysis revealed two distinct populations; monoclonal B cells (kappa+) and abnormal plasma cells (CD19-/CD56+/lambda+). She expired 19 days after admission due to septic shock. This is a rare case of WM exhibiting a light chain discrepancy between monoclonal B lymphocytes and paraprotein-secreting plasma cells. Light chain restriction may occur distinctly between lymphocyte and plasma cell populations in WM.