A10: Younger Age and Severity of Renal Presentation Distinguishes Microscopic Polyangiitis From Granulomatosis With Polyangiitis in Children: An ARChiVe Study

Background/Purpose: Comparisons of pediatric ANCA-associated vasculitis subtypes (AAV) are limited by the paucity of reported cases, standardized definitions, and overlapping classification criteria. Published work from ARChiVe (A Registry for Childhood Vasculitis) demonstrated modifications of validated classification algorithms applied to pediatric patients with AAV can classify each patient to mutually exclusive diagnostic categories. We compared presenting features of children with microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA) classified according to this methodology. Methods: A pediatric modification of the European Medicines Agency (EMA) algorithm for classifying AAV and polyarteritis nodosa (incorporating the EULAR/PRINTO/PRES pediatric classification criteria for GPA) was applied to patients in ARChiVe censored to April 2012. We compared characteristics of patients classified as having MPA and GPA. STATA (Statcorp, 2013) was used to calculate frequencies, percentages, and chi-squared with fisher's exact for categorical variables and means, standard deviations, and t-tests for continuous variables. Results: One hundred fifty-two of 227 children in ARChiVe met criteria for diagnosis of MPA (n = 22) or GPA (n = 130). Characteristics and presenting features are shown in Table 1. Children with MPA were younger at diagnosis (mean diff. 2.7y, p = 25% lower limit of normal 8 (89) 18 (36)