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Background: Immunoglobin A (IgA) vasculitis (IgAV) and anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) are small vessel vasculitis. IgAV is characterized by IgA1-dominant immune complexes deposition at vessel walls (Type III hypersensitivity reaction). By contrast, AAV is mediated by ANCA (Type II hypersensitivity reaction). Therefore, immunological pathogenesis is very different. Renal involvement is a common and potentially severe manifestation in both diseases. Objectives: To compare a) immunological analytical findings and b) renal outcome in a series of patients with renal involvement due to IgAV and AAV. Methods: Observational study of patients with IgAV or AAV with kidney involvement from a single university hospital, from January 2021 to December 2023. At the time of diagnosis, serum immunological parameters (IgA for IgAV, ANCA for AAV and C3 and C4 for both) were collected. In addition, data of renal involvement (hematuria or proteinuria, renal insufficiency, nephritic or nephrotic syndrome), dialysis or transplant throughout the follow-up were recorded (Table 1). We defined: hematuria: presence of more than 2 red blood cells/field in urinary sediment; proteinuria >150 mg of protein in 24-hour urine; renal insufficiency: estimated glomerular filtration rate of less than 60 mL/min/1.73 m2; nephrotic syndrome: proteinuria > 3.5 g/24h/1.73 m2 and nephritic syndrome: edema, oliguria, proteinuria, hematuria (with blood casts and/or dysmorphic red blood cells in the urinary sediment), decreased glomerular filtration rate and arterial hypertension. A comparative study between groups was performed using Chi-square and Mann-Whitney U tests for qualitative and quantitative variables, respectively. PResults: We studied 49 IgAV (25 women/24 men); mean age 26±24.2 years (range 2-80 years) and 74 AAV (42 women/32 men); mean age 61.8±15.2 years (range 24-87 years) with kidney involvement. As expected, patients with IgAV are younger. Ten of 49 IgAV patients (20.4%) had elevated IgA levels at the time of diagnosis. In AAV group, ANCA were tested in 50 from tested positive for myeloperoxidase (67.57%), 22 for proteinase 3 (29.73%) and 2 for both (2.7%). C3 and C4 levels were in range in patients from both groups. There were significant differences in renal failure between the two groups of vasculitis patients (pConclusion: Compared to IgAV patients, patients with AAV are more susceptible to kidney failure and dialysis requirement, but it does not seem that complement levels can be a biomarker to determine which patients will present more severe kidney involvement. More research is needed to determine which immunological parameters may be useful in predicting a worse renal prognosis for both groups.REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests: Vanesa Calvo-Río Abbvie, Lilly, Grünenthal, AMGEN, MSD, Novartis, Galápagos, Vifor, GSK, Otsuka, Janssen, Mónica Renuncio García This work was partially supported by MTVAL22/01 from IDIVAL, Fabricio Benavides-Villanueva: None declared, Luis Martín-Penagos: None declared, Diana Prieto-Peña: None declared, Marcos López Hoyos: None declared, Ricardo Blanco Abbvie, Pfizer, Roche, Bristol-Myers-Squibb, Janssen, Lilly, Novartis, UCB, and MSD, Abbvie, MSD, Roche.
Calvo-Río et al. (Sat,) studied this question.