IgG4-Related Kidney Disease Following Autologous Bone Marrow Transplant: A Case Report

Introduction: IgG4-related disease (IgG4-RD) is a chronic relapsing autoimmune disease characterized by increased production of IgG-4 and tissue infiltration of IgG4 positive plasma cells. It can co-exist with or contribute to the pathogenesis of several autoimmune diseases. A systematic review of literature reveals no established relationship between autologous bone marrow transplant (ABMT) and IgG-4 RD. Our case explores a potential link between IgG4-RD and ABMT. Recognizing this association is key due to the treatable nature of early stage IgG4-RD Case Description: A 76-year-old man with history of multiple myeloma status post ABMT in 2017 and off all treatment for myeloma presented with an AKI and sub-nephrotic range proteinuria (UPCR 679 mg/g). Initial creatinine was 4.0 mg/dl, up from a baseline of 0.9 six months prior, and peaked at 5.8 during the hospitalization. He had no systemic signs or infectious symptoms. Autoimmune workup was remarkable for a weakly positive ANA, borderline positive dsDNA, low C3/C4, elevated IgG4, and positive IgM/IgG cryoglobulins. Kidney biopsy showed: marked lymphoplasmacytic interstitial nephritis characterized by > 10/HPF IgG4-positive plasma cells, with mesangial immune complex glomerulonephritis. IF showed full-house staining. Bone marrow biopsy performed 10 days prior to hospitalization showed 7% plasma cells. He was treated with prednisone 60mg daily, with a slow taper over 3 months followed by reinitiation of myeloma treatment for 4 months. Creatinine improved to 4.8 at discharge and further declined to 1.7 by five months follow up. Proteinuria decreased to 286 mg/g, and autoimmune markers—normalized or became negative within two weeks post-discharge Discussion: This case suggests a possible link between IgG4-related disease (IgG4-RD) and autologous bone marrow transplant (ABMT). Early recognition and prompt treatment with steroids led to marked improvement in renal function. We suspect IgG4-RD in this patient based on biopsy findings consistent with the disease, elevated serum IgG4 levels, absence of clinical another autoimmune condition, and the typical steroid-responsive course. While ABMT is known to cause immune dysregulation and has been associated with various autoimmune conditions, to our knowledge, no prior reports have described a connection between ABMT and IgG4-RDLight microscopy showing significant interstitial inflammation