Indeed, the presence of the monoclonal IgM/kappa gammopathy on initial electrophoresis, later findings of a B-cell infiltrate with monoclonal IgM/kappa (without classification) on bone marrow biopsy, and finally the diagnosis of DLBCL with similar IgM/kappa expression, all support this hypothesis which triggered a renal impairment (MGRS) before transforming to DLBCL. Here, CD40LG is linked to diffuse large B-cell lymphoma.