Polyclonal plasma cell proliferation with marked hypergammaglobulinemia and multiple autoantibodies.

A 77-yr-old man presented with marked peripheral blood and bone marrow plasmacytosis, marked hypergammaglobulinemia, and multiple autoantibodies. Serum protein immunofixation and immunophenotyping of bone marrow plasma cells by flow cytometry and immunohistochemistry disclosed polyclonal proliferation of plasma cells at various stages of differentiation. The presence of multiple autoantibodies in the patient's serum suggests that an autoimmune disease underlies the polyclonal proliferation of plasma cells.