AB0125 CLINICAL CHARACTERISTICS OF RHEUMATOID ARTHRITIS PATIENTS WITH IGG4-RELATED SYNOVITIS
Authors: L. F. Chen, X. Zhang, C. Chen, J. D. Ma, Y. Mo, J. Lin, Y. Y. Zou, D. H. Zheng, L. Dai
Journal: Annals of the Rheumatic Diseases (2021)

Background: Elevated serum IgG4 (sIgG4) and IgG4+ plasma cell tissue infiltration are outstanding features of IgG4-related disease (IgG4-RD). However, elevated IgG4 is not specific for IgG4-RD. Our previous study reported elevated sIgG4 in 46% of rheumatoid arthritis (RA) patients ( Mediators Inflamm 2014 ). Whether synovium from RA patients show similar characteristics of IgG4-RD and how about the clinical characteristics of RA patients with IgG4-related synovitis have not been reported yet. Objectives: To explore the serum and synovial IgG4 level and their correlation with disease indicators in RA. Methods: Active RA patients who underwent needle synovial biopsy with qualified synovium tissue were recruited. Demographic and clinical data were collected simultaneously. Synovium tissue were stained with H&amp;E for Krenn synovitis score and immunohistochemistry for positive cell densities of CD20, CD38, IgG and IgG4. Serum IgG4 level was detected by immunonephelometry. Results: Among 96 RA patients recruited, 74 (77.1%) were female, the median age was 55.0 (46.0~61.0) years, disease duration was 42.0 (12.0~120.0) months and SDAI was 31.2 (22.1~42.8). The median sIgG4 was 1.38 (0.86~2.42) g/L and 49(51.0%) patients had elevated sIgG4. Compared with those with normal sIgG4, RA patients with elevated sIgG4 had significantly higher levels of PrGA [7 (5~8) vs. 6 (4~7)], ESR [90 (64~116) mm/h vs. 61 (38~75) mm/h], CRP [46.20 (17.20~74.20) mg/L vs. 18.90 (9.46~49.20) mg/L], DAS28-ESR [6.3 (5.6~7.4) vs. 5.7 (4.7~6.4)], SDAI [34.2 (25.3~48.8) vs. 27.8 (18.9~35.9)] and HAQ-DI [1.70 (0.61~2.28) vs. 0.88 (0.40~1.75), all P &lt;0.05]. Meanwhile, they also showed significantly higher synovial counts of CD38+ plasma cells [1240(559~2290) /mm 2 vs. 1020(354~1777) /mm 2 ], IgG4+ plasma cells [106 (39~249) /mm 2 vs. 68 (3~123) /mm 2 ], and higher ratio of IgG4+/IgG+ plasma cells [26.3 (15.5~38.0) % vs. 15.2 (0.9~24.7) %, all P &lt;0.05]. The median IgG4+ plasma cells count was 83 (10~192) /mm 2 and median ratio of IgG4+/IgG+ plasma cells was 19.1 (8.4~31.5)%. Both of them correlated positively with ESR, CRP and sIgG4 (r=0.216~0.394, all P &lt;0.05). There were 46 (47.9%) patients with IgG4+ plasma cells &gt;10/HPF, who had significant higher ESR [86 (50~109) mm/h vs. 65 (40~84) mm/h] and CRP [43.35 (16.93~77.85) mg/L vs. 26.15 (9.54~52.53) mg/L, both P &lt;0.05] than those with IgG4+ plasma cells ≤10/HPF. There were 13 (13.5%) patients with the ratio of IgG4+/IgG+ plasma cells &gt;40%, and 11 (11.5%) patients with both IgG4+ plasma cells &gt;10/HPF and IgG4+/IgG+ plasma cells ratio &gt;40% (IgG4-related synovitis). RA patients with IgG4-related synovitis had significant higher ESR than the others [106 (53~125) mm/h vs. 69 (41~91) mm/h, P &lt;0.05]. There were 10 (10.4%) patients showing elevated sIgG4 and IgG4-related synovitis. Four patients completed 1-year follow-up and all of them achieved remission at 6 th month (SDAI≤3.3, Figure 1). Only one patient had radiographic progression at 12 th month. Figure 1. Dynamic disease activity of 4 RA patients with elevated sIgG4 and IgG4-related synovitis during 1-year follow-up. Conclusion: IgG4-related synovitis can be found in RA patients. Their clinical significance in disease characteristics and outcomes are worth further study. Acknowledgements: This work was supported by National Natural Science Foundation of China (no. 81971527, 81801606 and 81801605), Guangdong Natural Science Foundation (no. 2018A030313541 and 2018A030313690), Guangdong Medical Scientific Research Foundation (no. A2018062), Guangdong Basic and Applied Basic Research Foundation (no. 2019A1515011928 and 2020A1515110061), and Science and Technology Program of Guangzhou (no. 201904010088). Disclosure of Interests: None declared