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Editor,—Idiopathic sclerosing inflammation of the orbit (ISIO) is a rare but well described condition.1-4There is controversy as to whether it is a condition at one end of the spectrum of non-specific orbital inflammatory syndrome (pseudotumour)2 5 6 or whether it is a disease entity in its own right.1 Its aetiology is not known, although its association with systemic disease and multifocal fibrosclerotic conditions such as Reidel's thyroiditis, retroperitoneal fibrosis, mediastinal fibrosis, and idiopathic pachymeningitis suggests an immunological mechanism.2 4 5 7 An autosomal recessive inheritance is suggested by the pedigree of two offspring of a consanguineous marriage, who developed multifocal fibrosclerosis.8 Diagnosis is complicated by a wide variety of clinical features ranging from mild grittiness to a painful, fixed, blind eye.9 Often there are no features of active inflammation, and there may be aggressive local destruction of bone with invasion of adjacent structures including brain, meninges, and sinuses.4 6 Reliable differentiation from lymphoma is only possible with immunohistochemical studies. Management is difficult because of poor response to both steroids and radiotherapy.4-7 Kennerdell recommends early, aggressive treatment with surgery, steroids, radiotherapy, or a combination.10 Results of the use of systemic chemotherapeutic agents such as azathioprine and cyclophosphamide, in addition to the above modalities, have been reported by Rootmanet al.1
A 75 year old woman with bilateral proptosis, marked photophobia, and severe ocular discomfort was referred to the ophthalmology service for an orbital biopsy. She was being investigated for an IgM paraproteinaemia, and the proptosis combined with a haematological disorder suggested orbital lymphoma. There was a history of hypertension and, at presentation, she also had a lower respiratory tract infection.
She had a history of dry eyes, treated with hypromellose eye drops. On examination proptosis measured 23 mm on the right and 21 mm on the left. She had marked restriction of extraocular movement in all directions of gaze in both eyes (Fig 1). Visual acuity with pinhole was 6/9–1 right and 6/12+3 left. There was no relative afferent pupillary defect. Lacrimal glands were not palpable and the globes were tender. Palpebral apertures were 6 mm right and 7 mm left. Levator function was moderate (11 mm) in both eyes. Skin creases were absent bilaterally. The right lower lid was retracted 3 mm with entropion. There was no lid lag or lagophthalmos. The globes were resistant to ballotment. Slit lamp examination revealed bilateral chemosis, asymmetric sectoral vascular pannus containing telangiectatic lumps at the limbus, and extensive punctate corneal epithelial erosions. It was not possible to evert the upper lids. Fundal examination revealed pale optic discs and posterior pole drusen. There was no head or neck lymphadenopathy.
One mm computed tomography with coronal and sagittal reconstructions revealed a bilateral orbital homogeneous infiltrate of soft tissue density, extending preseptally. Calcification was seen bilaterally in the region of the lacrimal fossae and in the central orbit (Fig 2).
Under general anaesthetic, six biopsies were taken from the right lacrimal gland and the left limbal conjunctival mass. Intraoperative forced duction testing was positive in all directions. Histopathology showed monomorphic lymphoid aggregates and fibrous tissue foci entrapping small nerves, consistent with sclerosing lymphoma (Fig 3). The differential diagnosis was of sclerosing inflammation. Immunohistochemistry differentiated between these two entities, and the final diagnosis was confirmed to be idiopathic sclerosing inflammation of the orbit. Postoperatively, a short course of topical steroids was given for scleritis localised to a biopsy site. The histopathological changes showed minimal active inflammatory changes, and the disease process was so far advanced that anti-inflammatory treatment was not considered helpful in this patient. Symptomatic relief was provided with topical lubricants.
Calcification of the orbit has not previously been described in idiopathic sclerosing inflammation of the orbit. The presence of calcification would be consistent with lymphoma, and idiopathic sclerosing inflammation of the orbit may be missed on histopathological examination if the diagnosis is not considered. This case demonstrates the difficulties associated with the diagnosis of idiopathic sclerosing inflammation of the orbit. It also demonstrates and confirms orbital calcification as part of the disease process, and we recommend that idiopathic sclerosing inflammation should be considered in the differential diagnosis of calcification within the orbit.