IgG4-related kidney diseases and conditions: Renal pelvic and ureteral diseases

Abstract

In the literature on IgG4-related urinary tract diseases, reports of cases with involvement of the renal pelvis and ureters are increasing. IgG4-related renal pelvic and ureteral lesions accompany extra-renal organ involvement, including IgG4-related type 1 autoimmune pancreatitis, sialadenitis, and orbital disease, and are characterized by the common pathological features of IgG4-related disease (IgG4-RD), including substantial numbers of IgG4-positive plasma cells, storiform fibrosis, and stenosis in the affected organs. Similar to other mucosal organs affected in IgG4-RD, these inflammatory findings are observed within the fibroadipose tissue in the renal hilum and around the ureters. The urothelial epithelium covering the renal pelvis and ureter is preserved. Nodular lesions such as pseudotumors can also form and it is important to differentiate these from malignant tumors. At present, comprehensive diagnostic criteria that include pathological parameters have been proposed for IgG4-RD; however, obtaining diagnostic findings in small biopsy specimens is often challenging. Therefore, the diagnosis can only be rendered following careful consideration of the patient’s clinical, serologic, radiologic, and pathologic features, including the possibility of involvement in other organs.