Three patients showed a pleomorphic lymphoid proliferation in their bone
marrow quite similar to that seen in W.M. but had a serum monoclonal Ig
belonging to the IgG (two cases) or IgA (one case) class. The bone marrow
plasma cells and a small percentage of lymphocytes contained intracytoplasmic
IgG or IgA whereas 30%-60% of blood lymphocytes and most
bone marrow lymphocytes carried the corresponding monoclonal 5.1g. The
findings thus differed from W.M. only by the heavy chain class of the Ig
and by the absence of S.Ig on plasma cells.