Diffuse large B cell lymphoma in a preceding IgG4-related disease with kidney restricted lambda light chain expression: case report and literature review

IgG4-related disease (IgG4-RD) is a newly classified but poorly understood immune-medicated systemic disease. It causes potential fibroinflammation in one or more organs, characterized by tumescent organs and marked IgG4-positive plasma cells infiltration in the affected tissues. There have been a few cases revealing close relationship between IgG4-RD and formation of B cell lymphoma. Diffuse large B cell lymphoma (DLBCL) and extranodal marginal zone lymphoma (EMZL) of mucosa-associated lymphoid tissue are the most common sub-types ever described, whereas the exact mechanism remain unclear. We report a 64-year old Chinese male who presented chronic kidney disease and was initially diagnosed typical IgG4-RD. Pathological findings revealed there was restricted expression of lambda light chain in the kidney. There was also elevated uptake abnormality observed in 18F-FDG-PET/CT. Prednisone combined with oral cyclophosphamide helped the patient to get a partial remission of renal function and an obvious decrease of IgG4 level. However, he developed DLBCL 16 months after IgG4-RD diagnosis. The DLBCL is speculated to transform from a pre-existing but possible missed diagnosed EMZL. Concurrent IgG4-RD with kidney-origin EMZL developing DLBCL has never been reported in the literature. Clinicians should keep in mind that lymphoma may occur in IgG4-RD. The mechanism of lymphomagenesis potential in IgG4-RD needs further study.