Cryoglobulinemia in primary Sjögren's syndrome: a monoclonal process.

Patients with primary Sjögren's syndrome have in their sera and urine free light chains or monoclonal immunoglobulins. In addition, they have mixed monoclonal (IgM kappa) cryoglobulinemia, which is associated with extraglandular disease and greater incidence of autoantibodies. In the present study, it is demonstrated by a high resolution agarose gel electrophoresis, combined with immunofixation, that nine patients with primary Sjögren's syndrome have mixed monoclonal (IgM kappa) cryoglobulins, in contrast to those observed in five patients with secondary Sjögren's syndrome (Sjögren's syndrome and rheumatoid arthritis), 13 patients with rheumatoid arthritis and six patients with systemic lupus erythematosus, which were mixed polyclonal.