Unilateral orbital mass as the initial presentation of pediatric antineutrophil cytoplasmic antibody associated vasculitis: eosinophilic granulomatosis with polyangiitis versus granulomatosis with polyangiitis

Isolated orbital inflammation may represent an initial manifestation of ANCA-associated vasculitis in pediatric patients. Although eosinophil-rich granulomatous inflammation and MPO-ANCA positivity may suggest eosinophilic granulomatosis with polyangiitis, predominant orbital and ENT involvement in the absence of asthma or other atopic features may be more consistent with localized granulomatosis with polyangiitis. This case underscores the importance of early orbital biopsy, comprehensive serological evaluation, and cautious interpretation of residual orbital lesions within a multidisciplinary, longitudinal diagnostic approach.