Abstract

Background: S100A8/A9 molecule or calprotectin has a significant role in innate immunity. This heterodimer of two S100 proteins has cytotoxic and proinflammatory properties, monitors cell proliferation and differentiation, and it is also an indicator of monocyte and neutrophil activity. Although it plays a significant role in many inflammatory rheumatic diseases, little is known about the significance of S100A8/A9 in patients with IgA vasculitis (IgAV) [1]. Objectives: We aimed to investigate S100A8/A9 in activity assessment and clinical monitoring of patients with IgA vasculitis. Methods: Patients were diagnosed with IgAV according to the EULAR/PRES/PRINTO criteria. In a prospective study, serum S100A8/A9 values were monitored in patients with IgAV at the beginning of the disease, after 3 and 6 months from the onset of the disease, and were compared with the values in the control group of patients who did not have acute or chronic inflammatory disease. They were also compared with the values of other inflammatory markers, as well as the clinical manifestations of the disease itself. Results: In patients with IgAV at the beginning of the disease, S100A8/A9 values were higher than in the control group (5740 ng/mL, CI 4982-6499; 1447 ng/mL, CI 1143-1751; p<0.0001). The values were also higher in patients with signs of active disease, regardless of the time of sample collection, compared to the control group (p<0.0001). Also, in patients who had an active disease after 3 months, higher values were observed compared to those in remission (4386±899.4 vs. 2294±1846; p=0.0260). Comparing the values of S100A8/A9 with other indicators of inflammation, a positive correlation was observed with the values of CRP (p=0.0076), ferritin (p=0.0077), C3 (p=0.0065) and fibrinogen (p=0.0019), while for the erythrocyte sedimentation rate we did not found statistically significant association, although it is possible that it exists (p=0.0725). It was also shown that the values of S100A8/A9 in the serum increase depending on the skin surface area covered by the rash (p=0.0376). Conclusion: So far, the few studies of S100A8/A9 values in the serum of patients with IgAV suggested that S100A8/A9 could be a predictor of disease severity in patients with IgAV. This study showed that S100A8/A9 values were significantly higher in patients with active disease compared to the control group and patients in remission. Therefore, this molecule could serve as an indicator of disease activity and be useful in the clinical monitoring of patients. SUPPORT: Croatian Science Foundation Project IP-2019-04-8822. REFERENCES: [1] Jelusic M, Sestan M, Giani T, Cimaz R. New Insights and Challenges Associated With IgA Vasculitis and IgA Vasculitis With Nephritis-Is It Time to Change the Paradigm of the Most Common Systemic Vasculitis in Childhood? Front Pediatr. 2022;10:853724. Acknowledgements: NIL. Disclosure of Interests: None declared.