Galactose-deficient immunoglobulin A1 (Gd-IgA1) was recently identified as a critical effector molecule in the pathogenesis of IgA nephropathy (IgAN). Gd-IgA1 is produced by the mucosal immune system. IgAN is thought to develop because of the deposition of a circulating immune-complex containing Gd-IgA1 in the kidney. Multicentric Castleman's disease (MCD) is a rare non-neoplastic lymphoproliferative disorder. As an etiology model, hypercytokinemia, including increased levels of interleukin-6, is the primary pathogenesis of many MCD cases. Here, we present two cases of mesangial proliferative glomerulonephritis with MCD. According to renal biopsy findings, one was diagnosed with non-IgAN and the other with IgAN. Surprisingly, in both cases, Gd-IgA1 was produced by plasma cells in the lymph nodes, suggesting that Gd-IgA1 production alone does not cause IgAN; rather, it may be produced without induction by mucosal immunity. Our findings demonstrate the diversity of the development of IgAN and help to reconsider the onset mechanism of IgAN.
Keywords: Anti-galactose-deficient IgA1 antibody; Castleman's disease; IgA nephropathy; Mucosal immunity.
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