Orbital Granulomatosis With Polyangiitis Mimicking IgG4-Related Disease in a 12-Year-Old Male

Granulomatosis with polyangiitis is rare in children. We report a case of a 12-year-old male who presented with new symptoms of left eyelid swelling and ptosis. Magnetic resonance imaging showed an enhancing orbital mass suspicious for a neoplasm. Excisional biopsy was performed. Microscopic examination revealed fibrovascular tissue with dense collagenous fibrosis and mixed inflammatory infiltrate that included many plasma cells. Many small and medium-sized blood vessels showed granulomatous and necrotizing vasculitis with disruption of the vessel walls and fibrinoid necrosis. Immunostain for IgG highlighted the numerous plasma cells, approximately 50% of which were positive for IgG4 immunostain. A diagnosis of granulomatosis with polyangiitis was suggested, with recommendation of serologic testing for anti-neutrophil cytoplasmic antibodies. Serum anti-neutrophil cytoplasmic antibodies were borderline high with a cytoplasmic staining pattern. The patient improved with steroid and methotrexate therapy. Gra...