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A case of orbital xanthogranuloma is presented. The radiological and clinicopathological feature of diffuse periosteal infiltration, to the authors’ knowledge, has never previously been reported.
A 64 year old woman was referred to the orbital clinic with a 2 year history of bilateral yellow cutaneous lesions on the upper and lower eyelids. She was otherwise well, under regular haematological review for a monoclonal gammopathy of uncertain significance. Examination revealed firm subcutaneous masses underlying the skin lesions, bilateral yellow episcleral infiltrates inferotemporally, and 2 mm bilateral proptosis (Hertel readings 24 mm each eye at 110 mm) (Fig 1). Eye movements were full, and the remaining ocular and systemic examinations were unremarkable. Investigations carried out by her haematologist included a bone scan, electrocardiogram, and liver and renal function tests, all of which were normal. Orbital computerised tomography (CT) demonstrated bilateral extraocular muscle enlargement and periosteal infiltration involving the entire periorbita, from the orbital margin to the apices. (Fig 2) Biopsies of the skin, episcleral, and periosteal lesions all confirmed xanthogranuloma with S100 negative, CD68 positive foamy histiocytes, and Touton giant cells. The collagenous stroma showed no foci of necrosis and Langerhans cells were not seen. Electron microscopy was not performed.
The patient has been observed for 12 months, and remains asymptomatic, with no change in the clinical findings.
Adult xanthogranulomatous disease is defined histopathologically, by S100 negative foamy histiocytes and Touton giant cells. Categories, based on systemic and histopathological findings, include adult onset xanthogranuloma, adult onset asthma with periocular xanthogranuloma, necrobiotic xanthogranuloma (NBX), and Erdheim-Chester Disease (ECD).1 They may also be classified as a form of non-Langerhans cell histiocytosis, involving soft tissues of the orbit rather than bone (bony involvement being a major feature of Langerhans cell histiocytosis).2
Miszkiel et al3 reported the radiological and clinicopathological features of orbital xanthogranuloma to include cutaneous periocular lesions and proptosis, largely due to an infiltrating soft tissue orbital mass. Local orbital involvement includes enlargement and infiltration of extraocular muscles, lacrimal gland, retrobulbar fat, and encasement of the optic nerve. Orbital involvement in ECD is rare, and usually bilateral.4,5 Local orbital bone destruction has been reported in juvenile xanthogranuloma.6,7
To the authors’ knowledge, the presence of diffuse periosteal infiltration, confirmed histologically to be xanthogranuloma in the above case, has never previously been reported.
There were no features of bony destruction, and the patient did not have any systemic involvement suggestive of ECD, confirmed by the normal investigations carried out by her haematologist. Necrosis of collagenous stroma, diagnostic of NBX, was also not seen histologically.
The prognostic importance of diffuse periosteal infiltration remains unknown, as our patient has no functional symptoms due to xanthogranuloma, or the monoclonal gammopathy, for which she remains under haematological review.