#813 Clinical and laboratory manifestations of kidney damage in various types of ANCA-associated vasculitis

Abstract Background and Aims The kidneys are one of the most vulnerable organs in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis. Kidney damage can significantly worsen the prognosis and quality of life of patients. Clinical and laboratory manifestations of renal dysfunction vary depending on the subtype of disease and the degree of vascular damage. The aim of this study is to analyze the clinical and laboratory manifestations of renal pathology in patients with various types of ANCA-associated vasculitis. Method The study included 45 patients diagnosed with ANCA-associated vasculitis (60.0% (n = 27) women and 40.0% (n = 18) men), who were observed at the Minsk Scientific and Practical Center for Surgery, Transplantology and Hematology from 2017 to 2024. The average age was 59.1 ± 12.3 years. 57.8% (n = 26) patients had granulomatosis with polyangiitis (GPA), 24.4% (n = 11)—microscopic polyangiitis (MPA), 17.8% (n=8)—eosinophilic granulomatosis with polyangiitis (EGPA). We analyzed blood creatinine levels, estimated glomerular filtration rate (eGFR), hematuria, leukocyturia, cylindruria and daily proteinuria at the time of disease onset to assess the type and severity of renal damage. In addition to clinical and laboratory examination, the diagnosis of ANCA-associated vasculitis and secondary glomerulonephritis was confirmed by the results of immunological tests (ANCA, antibodies to myeloperoxidase and proteinase-3) and nephrobiopsies. Results A higher level of serum creatinine (237 (103; 463) μmol/l) and low eGFR (18.1 (12.3; 76.2) mL/min/1.73 m²) were diagnosed in the group of patients with MPA compared with the GPA and EGPA groups (P < 0.005). Proteinuria was diagnosed in 75.6% (n = 34), most often—in patients with MPA (90.9%). The level of proteinuria ranged from mild to nephrotic. It exceeded 1 g/day in 66.7% (n = 30). Nephrotic syndrome was found in 8.9% (n = 4) patients and was not observed in EGPA group. In 9 cases (20.0%) isolated urinary syndrome was diagnosed, but without significant decrease in renal function and arterial hypertension. In 42.2% (n = 19) cases kidney damage was accompanied by arterial hypertension, its highest frequency was recorded in the MPA group: 7 out of 11 patients (63.6%). eGFR <90 ml/min/1.73 m² was found in 82.2% (n = 37) patients, 20.0% (n = 9) showed the most pronounced decrease (eGFR <15 ml/min/1.73 m²), mainly in MPA group (n = 7), P < 0.05. The clinical picture of rapidly progressive glomerulonephritis developed in 63.6% (n = 11) of patients with MPA, while in the GPA and EGPA groups this figure was 23.1% (n = 6) and 12.5% (n = 1), P < 0.05, respectively. Conclusion Variants of ANCA-associated vasculitis exhibit a wide range of clinical and laboratory manifestations, with the most severe forms of renal damage reported in patients with MPA. Proteinuria is detected in a significant number of patients, especially with MPA. Nephrotic syndrome developed in 8.9% of patients and was absent in the EGPA group. Kidney damage is often accompanied by arterial hypertension, which is most pronounced among patients with MPA. The incidence of rapidly progressive glomerulonephritis supports the fatal role of renal damage in ANCA-associated vasculitis.