Clinical Characteristics of Patients With IgG4-Related Disease Complicated by Hypocomplementemia
Yuya Fujita, Shoichi Fukui, Masataka Umeda, Sosuke Tsuji, Naoki Iwamoto, Yoshikazu Nakashima, Yoshiro Horai, Takahisa Suzuki, Akitomo Okada, Toshiyuki Aramaki, Yukitaka Ueki, Akinari Mizokami, Tomoki Origuchi, Hiroshi Watanabe, Kiyoshi Migita, Atsushi Kawakami
Abstract
Background: A proportion of patients with immunogloblin G (IgG) 4-related disease (IgG4-RD) have hypocomplementemia. We aimed to identify characteristics of such patients. Methods: We analyzed the demographic and clinical data and complement levels of 85 patients with IgG4-RD. We defined hypocomplementemia as serum C3 and/or C4 levels below the lower limit of normal at diagnosis. We also compared the characteristics of patients with and without IgG4-RD. Results: Thirty-two (38%) patients had hypocomplementemia at diagnosis. Patients with hypocomplementemia had more lymph node (p < 0.01), lung (p < 0.01), and kidney (p = 0.02) involvement and a higher IgG4-RD responder index than those without (p = 0.05). Additionally, patients with hypocomplementemia had significantly higher IgG (p < 0.01), IgG4 (p < 0.01), and soluble interleukin 2-receptor (sIL-2R) (p < 0.01) levels and total IgG minus IgG4 (p < 0.01). C3 and C4 levels negatively correlated with IgG, IgG4, and sIL-2R levels, total IgG minus IgG4, and number of IgG4-RD responder index: a measure of the disease activity in IgG4-RD. Patients with hypocomplementemia at diagnosis had a significantly higher frequency of relapse (p = 0.024), as determined using the log-rank test. A multivariate logistic regression analysis showed the presence of hypocomplementemia was independently associated with relapse (OR, 6.842; 95% confidence interval [95%CI], 1.684-27.79; p = 0.007). Conclusions: Patients with IgG4-RD with hypocomplementemia have a more active clinical phenotype, suggesting contributions of the complement system in the pathophysiology of IgG4-RD.