An additional patient with W.M. and a serum 1gM A had been followed and
treated for several years when a second serum monoclonal Ig (IgG K) appeared.
In the bone marrow, two populations of plasma cells containing either p. and
A or y and K chains were found by intracytoplasmic staining. Surface immunofluorescence
demonstrated two distinct lymphocyte clones in bone marrow
and blood characterized by p.A and 7K S.Ig markers, respectively.