Clinical Characteristics and Outcomes of Pediatric Patients with ANCA-Associated Vasculitis: Single-Center Inception Cohort

Background: Anti-neutrophil cytoplasmic autoantibody (ANCA)-vasculitis (AV) is a chronic autoimmune disorder characterized by small vessel inflammation and necrosis. Autoantigens include myeloperoxidase (MPO) and proteinase 3 (PR3) and mounting evidence suggests ANCA specificity better predicts prognosis than clinical phenotype. Pediatric AV is extremely rare, and treatment and prognosis are often based on adult data. We aimed to describe the clinical characteristics and outcomes by ANCA specificity. Methods: Patients ≤18-years at AV diagnosis from the Glomerular Disease Collaborative Network were included. Key outcomes were end-stage kidney disease (ESKD), death, relapse, and remission. Baseline characteristics and treatment were analyzed in relation to outcomes. Continuous variables and categorical variables were compared using Mann-Whitney and Fisher’s exact test. Results: We identified 88 pediatric AV patients, 36 (41%) with MPO-ANCA and 31 (35%) with PR3-ANCA. MPO-ANCA patients were younger at diagnosis (13.5 years) compared to PR3-ANCA patients (15 years). Microscopy polyangiitis (MPA) was most common (67%) among MPO-ANCA patients, and granulomatosis with polyangiitis was most common (62%) among PR3-ANCA patients (p < 0.05). All renal-limited patients were MPO-ANCA positive. A higher proportion of MPO-ANCA patients had renal involvement (97%, p <0.05), while PR3-ANCA patients had more sinus manifestations (71%, p <0.05). 33% of pediatric AV patients reached ESKD, and MPO-ANCA positivity was associated with worse kidney outcomes within 5 years of diagnosis. (Figure 1) Conclusion: In this large, single-center cohort of pediatric AV patients, MPO-ANCA positivity was associated with younger age, MPA phenotype, and renal-limited disease. Like previously published cohorts, a significant proportion of pediatric AV patients reached ESKD, and MPO-ANCA positivity was associated with worse kidney outcomes within 5 years of diagnosis.