Organ-limited ANCA-associated orbital inflammatory disease: a diagnostic challenge.

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a group of autoimmune disorders that cause inflammation and necrosis of small- to medium-sized blood vessels. It most commonly affects the kidneys and lungs, leading to complications such as rapidly progressive glomerulonephritis and pulmonary haemorrhage. Ocular involvement occurs in up to 50% of patients with AAV, most commonly presenting as scleritis, episcleritis, or orbital inflammatory disease (also known as orbital pseudotumor). Other ocular findings may include keratitis, uveitis, or retinal vasculitis. Eyelid necrosis with destructive orbital inflammation, however, is extremely rare and poses a significant diagnostic challenge because its presentation can mimic infections, malignancies, or other inflammatory orbital conditions. Prompt recognition is critical to prevent irreversible tissue damage and vision loss. We report the case of a 74-year-old Hispanic woman with multiple vascular risk factors who presented with recurrent pustules of the right upper eyelid that progressed to full-thickness eyelid necrosis, medial orbital mass effect, and corneal compromise. Initial management was directed toward presumed orbital cellulitis; however, orbital imaging revealed a destructive extraconal mass with mass effect and associated venous stasis. Sequential biopsies demonstrated extensive necrosis with histiocytoid granulomatous inflammation and focal features of chronic vasculitis. Negative stains and cultures excluded infectious and neoplastic causes. After thorough evaluation and exclusion of alternative etiologies, the findings were most consistent with ANCA-negative ANCA-AAV. The patient was treated with high-dose intravenous corticosteroids and rituximab induction, resulting in stabilization of orbital disease and preservation of vision. This case highlights the potential for destructive orbital vasculitis to masquerade as infection or malignancy and underscores the importance of considering AAV in atypical orbital presentations. Prompt recognition and initiation of immunosuppressive therapy are critical to prevent irreversible morbidity.