Waldenström's macroglobulinaemia with anti-IgG activity: a series of five cases.

Clinical, serological and cellular studies were carried out in five cases of Waldenström's macroglobulinaemia with cryoglobulinaemia of the mixed IgM–IgG type and extremely high serum levels of rheumatoid factor activity. Clinically, no joint involvement or other distinctive features were found in these patients, as compared with other cases of primary macroglobulinaemia without anti-γ-globulin activity. The isolation of the monoclonal IgM immunoglobulins, as well as absorption studies with IgG and immunocytological investigations demonstrated that the whole of the rheumatoid activity was associated with the Waldenström-type paraproteins. Such cases seem to represent instances of a rheumatoid factor monoclonal gammapathy, in fact a subgroup of Waldenström's macroglobulinaemia, in view of the presence of an IgM paraprotein, possessing anti-IgG activity, synthesized by the lymphocytoid cells infiltrating the bone marrow.