Clinical, Serologic, and Histologic Characteristics of Pauci-Immune Renal Vasculitis and Its Response to Treatment in a Mexican Population

Background: Small-vessel vasculitis presents an adverse renal prognosis that can be life-threatening, so it is relevant to know its characteristics and response to treatment Methods: Retrospective cohort study, conducted between April 2018 and April 2024. The objective was to analyze the characteristics of pauci-immune renal vasculitis and its response to treatment in a third level hospital in Mexico. Patients older than 18 years with a biopsy-proven diagnosis, who had a follow-up of at least 12 months were included Results: 19 patients were evaluated, with average age 54 years, 13 (68.42%) women. 14 (73.68%) had extra-renal manifestations. In the histological classification 6 (34.58%) were mixed, 5 (26.32%) focal, 4 (21.05%) sclerotic, 3 (15.79%) crescentic and 1 not classified. 9 (47.37%) were associated with MPO, 7 (36.84%) with PR3, and 3 (15.79%) seronegative. 7 (36.84%) had decreased Complement C3 (< 90 mg/dl). At diagnosis, 16 (84.21%) patients had deterioration of the glomerular filtration rate (eGFR < 60 ml/min/1.73m2) and 9 (47.37%) required renal replacement therapy (RRT). As induction treatment all patients received steroids, 6 (31.58%) cyclophosphamide (CYC), 6 (31.58%) rituximab (RTX), 5 (26.32%) CYC + RTX and one mycophenolic acid (Table 1). Until April 2024, patients were followed up for a mean of 31 months, 14 (73.68%) are free of RRT and one (5.26%) died Conclusion: Deterioration of the GFR was the main renal manifestation. The most common serology was associated with MPO (47.37%). Although not frequently reported, we found C3 hypocomplementemia in 7 (36.84%) patients. The survival of the patients (94.74%) and their renal prognosis (78.95% without RRT) were better than those reported in other populations. The efficacy of the treatments is similar among the regimens we evaluated