A case of type 2 diabetes mellitus complicated with IgG4-related retroperitoneal fibrosis and a literature review.

IgG4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory disorder that can affect multiple organs throughout the body, predominantly in middle-aged and elderly males, with a male-to-female ratio of 2꞉1 to 3꞉1. IgG4-related retroperitoneal fibrosis (IgG4-RPF), a rare subtype of IgG4-RD, has an unclear etiology, and its comorbidity with type 2 diabetes mellitus is also uncommon. A lack of awareness of this condition in clinical practice can easily lead to misdiagnosis. On July 14, 2016, the Third Xiangya Hospital of Central South University admitted a patient with type 2 diabetes mellitus complicated by IgG4-RPF. Following comprehensive treatment, including blood glucose and blood pressure control, kidney protection, circulation improvement, and the use of prednisone, the patient's condition significantly improved. The retroperitoneal fibrotic mass decreased in size, renal function improved, and serum IgG4 levels decreased. After 8 years of follow-up, the condition did not recur. Analyzing this case in conjunction with a literature review suggests that the development of IgG4-RPF in diabetic patients may be related to chronic inflammation from metabolic syndrome and atherosclerotic plaques associated with long-standing diabetes. This provides valuable clinical ideas for clinicians in diagnosing and treating this rare comorbidity.