Lymphoproliferative disorders in Japanese patients with Sjögren's syndrome.

Fourteen Sjögren's syndrome (SS) patients with monoclonal gammopathy (MG), 4 SS patients with malignant lymphoma (ML) and one with pseudolymphoma (PL) were described. Among the 14 MG patients, the IgG class was found in 3, IgA in 6, IgM in 3, and 2 M proteins (IgM/IgG and IgA/IgG) were found in 2 patients. The monoclonal rheumatoid factor (RF) was found in 4 patients (3 IgA and one IgM). Idiotypes (Id) of M proteins were studied in 11 out of 14 patients. The histology of ML showed the diffuse, large cell, medium-sized cell and follicular, mixed cell type. The monoclonal surface membrane Ig (SmIg) and/or cytoplasmic Ig (CIg) were identified (3 IgM and one IgG). A review of the Japanese literature on lymphoproliferative disorders (LPD) in SS patients disclosed additional 15 MG patients (3 IgG, 5 IgA, 6 IgM and one Bence Jones protein) and 22 LPD patients (14 non-Hodgkin's ML, 4 PL, 2 plasmacytomas and 2 thymomas). The literature was also reviewed on LPD in non-Japanese SS patients; 26 patients with MG (4 IgG, 2 IgA, 19 IgM and one Bence Jones protein) and 104 patients with LPD (59 non-Hodgkin's ML, 4 Hodgkin's lymphomas, 23 PL, 5 thymomas, 4 immunoblastic lymphadenopathies (IBL), 2 Lennert's lymphomas and 7 others) were found. These results indicate that non-IgM class MG was more dominant in Japanese than in non-Japanese SS patients and that there was a higher incidence of MG in primary than in secondary SS patients, and also that B cell lymphomas (9 in Japanese and 11 in non-Japanese) were more common in SS patients.