A Curious Case of Pediatric Granulomatosis and Polyangiitis

Granulomatosis with polyangiitis (GPA), formerly known as Wegener's granulomatosis, is a rare, systemic autoimmune disease characterized by granulomatous inflammation and necrotizing vasculitis. While most cases occur in adults, pediatric presentations are becoming more recognized, often with atypical symptoms. We present the case of a 9-year-old girl who presented with a 3-week history of unilateral proptosis, a persistent cough, and mild fatigue. Her presentation and findings varied between infection and the inflammatory process. Histopathology of an orbital and ethmoid sinus biopsy revealed caseating and non-caseating granulomas, which further complicated the differential diagnosis. The patient also had an infection with <i>Streptococcus viridans, </i>methicillin-resistant <i>Staphylococcus aureus </i>(MRSA), and <i>Staphylococcus epidermidis</i>. Laboratory findings showed elevated inflammatory markers and a positive antineutrophil cytoplasmic antibody (ANCA) at a later stage. This case highlights the challenges in diagnosing GPA in children, particularly with an unusual presentation, and emphasizes the importance of a multi-disciplinary approach and early immunosuppressive treatment to help reduce complications from this disease.