Disparities between IgG4-related disease with and without kidney involvement: a case-control study based on 450 patients

Abstract Background We aimed to compare the demographic, clinical and laboratory characteristics between IgG4-related kidney disease (IgG4-RKD+) and extrarenal IgG4-related disease (IgG4-RKD-) in a large Chinese cohort, as well as describing the radiological and pathological features of IgG4-RKD+.Methods We retrospectively analyzed the medical records of 450 IgG4-RD patients at Peking University People’s Hospital from January 2004 to January 2020.Results Among the 450 IgG4-RD patients, 66 were diagnosed with IgG4-RKD+. Compared with IgG4-RKD- patients, IgG4-RKD+ patients had older age at onset and at diagnosis (59 vs 54, P=0.007; 61 vs 56, P=0.002, respectively). Male to female ratio of IgG4-RKD+ patients is significantly higher (2.5:1 vs 1.2:1, P=0.015). In the IgG4-RKD+ group, the most commonly involved organs were salivary gland (54.6%), lymph nodes (47.0%) and pancreas (40.9%). More than three organs involved (OR=6.212), retroperitoneal fibrosis involvement (RPF) (OR=12.460) and low serum C3 level (OR=0.202) were risk factors for the kidney disease in IgG4-RD patients. It was found that renal function was impaired in more than 50% of IgG4-RKD+ patients. The most common imaging finding is multiple, often bilateral, hypodense lesions, followed by ureteric obstruction and hydronephrosis related to RPF, and thickening of the renal pelvic wall. Conclusions Involvement of three or more organs, retroperitoneal fibrosis and low serum C3 level were risk factors for the kidney disease in IgG4-RD patients. These findings indicate potential differences in pathogenesis of these two phenotypes.