Orbital xanthogranulomatous disease: a rare presentation of adult-onset xanthogranuloma.

We describe the case of a young adult woman presenting with progressive bilateral proptosis, periorbital soft tissue swelling and eyelid skin lesions. Imaging showed thickened eyelids and enlarged lacrimal glands and extraocular muscles, and a biopsy of the eyelid disclosed a xanthogranulomatous lesion with increased IgG4+ plasma cells. Further investigation did not reveal any associated systemic findings, and the diagnosis of adult-onset xanthogranuloma was made. Periocular lesions and proptosis responded to oral steroids, but symptoms recurred on tapering. Sustained remission was achieved with low-dose corticotherapy. Adult orbital xanthogranulomatous disease comprises a group of rare histiocytic disorders, and pathology is the key to diagnosis. It can be classified into four syndromes with different systemic manifestations and prognoses, adult-onset xanthogranuloma being the least common. Definitive classification is often challenging and requires thorough pathological review and long-term clinical monitoring. Limited evidence is available for the treatment of these conditions, but a conservative approach with immunosuppression is usually considered the best option.