Date: Monday, November 6, 2017
Session Title: Miscellaneous Rheumatic and Inflammatory Diseases Poster I
Session Type: ACR Poster Session B
Session Time: 9:00AM-11:00AM
Background/Purpose: Hypocomplementemia frequently occurs in IgG4-related disease (IgG4-RD), especially IgG4-related kidney disease (IgG4-RKD). This study aimed to investigate the clinical features of IgG4-RD patients (pts) with hypocomplementemia using a large-scale cohort of 328 IgG4-RD pts, in order to clarify the clinical significance and mechanisms of hypocomplementemia.
Methods: We retrospectively evaluated the clinical features at diagnosis of 328 pts diagnosed with IgG4-RD according to the comprehensive diagnostic criteria or each organ-specific diagnostic criteria; the features we evaluated included age; sex; serum IgG4, IgE, CH50, C3, C4, and CRP levels; gaps between serum IgG and IgG4 levels (IgG-IgG4 levels); the serum IgG4/IgG ratio; and the affected organs. These data were longitudinally analyzed over the clinical course for patients whose data were available. Hypocomplementemia was defined as a decrease below the normal range for the serum CH50, C3, or C4 level. We applied multivariate logistic regression analysis to the variables with P<0.05 in univariate analysis to search for factors related to hypocomplementemia in the group of all pts, pts with IgG4-RKD, and pts without IgG4-RKD.
Results: The pts comprised 201 men and 127 women (average age 63.9 years). At diagnosis, the average serum IgG4 level was 750 mg/dL (range: 18 to 3,510). Hypocomplementemia was observed in 138 pts (42.1%). The salivary glands were involved in 241 pts, lacrimal glands in 188, pancreas in 85, retroperitoneum/arteries in 82, kidneys in 80, and lungs in 76. Compared with pts without hypocomplementemia, pts with it had significantly higher age (65.0 vs. 63.0 years, P=0.044), serum IgG4 (947 vs. 608 mg/dL, P<0.001) and IgG-IgG4 levels (1,976 vs. 1,428 mg/dL, P<0.001), IgG4/IgG ratio (31.0% vs. 27.2%, P=0.028), and number of involved organs (3.5 vs. 3.0 organs, P=0.007). They also had a higher incidence of renal (34.8% vs. 16.8%, P<0.001), pancreatic (34.1% vs. 20.0%, P=0.005), and lung (29.7% vs 18.4%, P=0.024) involvement. Multivariate logistic regression analysis for all pts indicated that the elevation of IgG-IgG4 levels [per 100 mg/dL, odds ratio (OR) 1.102, 95% confidence interval (CI) 1.036-1.173, P=0.002] and the presence of pancreatic lesions (OR 1.909, 95% CI 1.063-3.428, P=0.031) were independent factors related to hypocomplementemia. Of note, the same analysis in pts with IgG4-RKD showed that only the elevation of IgG-IgG4 levels (per 100 mg/dL, OR 1.227, 95% CI 1.094-1.375, P<0.001) was an independent factor, whereas the presence of pancreatic lesions (OR 1.963, 95% CI 1.048-3.676, P=0.035), but not the elevation of IgG-IgG4 levels (OR 1.046, 95% CI 0.984-1.111, P=0.153), was an independent factor in pts without IgG4-RKD. In IgG4-RKD, both pts with and without hypocomplementemia showed serum IgG4 re-elevation upon relapse of renal lesions. Notably, the pts with hypocomplementemia showed exacerbation of hypocomplementemia and re-elevation of IgG-IgG4 levels, while the pts without it did not.
Conclusion: The present study shows that hypocomplementemia is related to the elevation of IgG subclasses other than IgG4 in IgG4-RD, especially IgG4-RKD.
To cite this abstract in AMA style:Mizushima I, Yamada K, Yamamoto M, Saeki T, Matsui S, Hara S, Takahashi H, Nomura H, Kawa S, Kawano M. Hypocomplementemia Is Closely Related to IgG Subclasses Other Than IgG4 in IgG4-Related Disease [abstract]. Arthritis Rheumatol. 2017; 69 (suppl 10). https://acrabstracts.org/abstract/hypocomplementemia-is-closely-related-to-igg-subclasses-other-than-igg4-in-igg4-related-disease/. Accessed February 3, 2023.
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