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Background: In the pathogenesis of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), neutrophils play a crucial role, serving as both the target cells attacked by ANCA and the main participating cells in regulating the inflammatory process. 1 Autoimmune and chronic inflammatory diseases can lead to abnormalities in leukocytes, particularly in polymorphonuclear cells (PMN), with neutrophils comprising the majority. Abnormal PMN morphologies may encompass hypo- and hyper-segmentation as well as immature forms. 2 There is a gap in the current literature regarding abnormalities in circulating leukocytes in patients in sustained remission. Objectives: The aim of this study is to investigate the different neutrophil phenotypes within three groups: granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and eosinophilic granulomatosis with polyangiitis (EGPA). Methods: We collected blood samples from adult patients affected by GPA, MPA and EGPA, classified according to the EULAR/ACR criteria 2022, who attended the outpatients Vasculitis Clinic of our University. All patients were no longer taking steroid therapy and were in the remission stage, as per the EULAR/ACR definition. A age- and sex- matched control group of healthy subjects was enrolled. May-Graunwald-Giemsa (MGG) staining of peripheral blood smears was used for studying cellular morphology. Results: Between may 2023 and November 2023, we enrolled 45 patients: 16 GPA patients, 13 MPA patients and 28 EGPA patients, of which 19 ANCA positive EGPA and 9 ANCA negative EGPA. Hence, we enrolled 28 matched healthy controls (HCs). No differences were observed among the three groups of AAV patients with respect to female sex (GPA=50%, MPA=46.2%, EGPA=46.4%, p=0.969), age at sampling (median and IQR, GPA=54 40-67, MPA=67 52-78, EGPA=62 55-71, p=0.172), disease duration at sampling (median and IQR, GPA=58 43-143, MPA=90 61-108, EGPA=78 36-124, p=0.818), time from steroid discontinuation (median and IQR, GPA=36 6-52, MPA=38 14-53, EGPA=18 9-48, p=0.567), and ongoing immunosuppressive therapy at sampling (n and %, GPA=12 75, MPA=9 69, EGPA=18 64, p=0.7611). A statistically significant increase in total PMN numbers was observed in AAV when compared to HC (median and IQR, HC 57.2 53.8 -64.0, GPA 69.3 57.7-79.60}, MPA 61.3 [52.6-67.3, and EGPA 62.3 53.2-73.1, p=0.0501). Hence, there was a statistically significant increase in the number of hypo-segmented in AAV patients (PMN: HC 7.5 6.3-8.7, GPA 18.7 14.9-20.8, MPA 12.7 9.6-18.5, and EGPA 9.2 5.5-13.0, pConclusion: Patients with AAV exhibit statistically significant increase in the number of PMNs, particularly in the count of hypo-segmented PMNs. Further prospective studies involving larger cohorts are needed to confirm these differences and explore whether distinctions exist between active and inactive patients. REFERENCES: 1 Ge S et al. Front Pharmacol. 2022;13:957660. 2 Baggio C et al. Int J Mol Sci. 2023;24(6):5450. Acknowledgements: NIL. Disclosure of Interests: None declared.
Iorio et al. (Sat,) studied this question.