Background: IgG4-related disease (RD) is a systemic condition that can affect nearly all organs. Renal involvement encompasses interstitial nephritis, membranous nephropathy, and renal infiltrative lesions. Symptomatic IgG4-related kidney disease (RKD) without extrarenal organ manifestations is an exceptionally rare occurrence.

Case Report: The authors present a case of 48-year-old male with isolated renal IgG4-RD presented with abdominal pain. Laboratory investigations revealed acute kidney injury, proteinuria, and hypoalbuminemia. Whole abdominal computed tomography (CT) scan disclosed infiltrative lesions in both kidneys and ureters, accompanied by hydronephrosis. Kidney biopsy demonstrated lymphocytic and plasma cell infiltration, with 82 plasma cells per high power field (HPF), storiform fibrosis, and the absence of obliterative phlebitis. After receiving corticosteroid treatment, the patient’s renal function improved, and the infiltrative lesions went into remission.

Conclusion: Isolated renal IgG4-RD is a rare and challenging diagnosis. The disease can manifest as acute interstitial nephritis, glomerular disease, retroperitoneal fibrosis, or, rarely, as mass or infiltrative lesions. Corticosteroid therapy is likely to yield favorable responses, hence, prompt diagnosis is crucial. Delayed diagnosis may result in organ fibrosis and dysfunction.

Keywords: IgG4-related disease; IgG4-related kidney disease; Infiltrative renal disease

DOI: 10.35755/jmedassocthai.2024.2.13940

Received 16 October 2023 | Revised 12 January 2024 | Accepted 12 January 2024