Sir,

We report a rare case of orbital xanthoma in a 38-year-old man presenting as droopy eyelid and proptosis. The only clue to the diagnosis was the presence of eyelid xanthelasma.

Introduction

Case report

A previously well 38-year-old Bangladeshi labourer presented with a 2-month history of worsening right ptosis, proptosis, and dull ache over the forehead (Figure 1). Examination revealed a right non-axial proptosis which measured 23 mm on Hertel's exophthalmometer (compared with 21 mm on the left). The right palpebral fissure measured 5 mm (compared with 7 mm on the left). The right upper eyelid had an area of xanthelasma in the nasal aspect; otherwise, it is not erythematous or tender to palpation. The ocular movement was normal except for dull ache and slight restriction on upgaze. The vision was normal in both eyes. An urgent CT scan revealed a mass which appeared to involve the superior rectus and levator superioris complex (Figure 2). A possible diagnosis of myositis was made and he was started on oral 100 mg diclofenac b.d. The blood tests for autoimmune antibodies, ESR, and thyroid function tests were normal. The only abnormal result was raised cholesterol level of 6.2 mmol/l. There was no clinical improvement after 2 weeks. A MRI scan was performed to elucidate the lesion. This showed the mass to be distinct from the superior rectus and appeared to involve only the levator superioris (Figure 3). An open biopsy through the skin crease revealed an uncapsulated orange coloured lesion between the orbicularis oculi and the orbital septum with infiltration of the levator aponeurosis (Figure 4). The lesion had a rubbery consistency and extended posteriorly beneath the orbital roof. The mass was removed en bloc. It had a uniform yellow surface measuring 2.1 × 1.5 × 1.1 cm. Postoperatively, there was a marked improvement of the proptosis. Histological report revealed a fibroadipose lesion made up of large number of macrophages with foamy cytoplasm and eccentric nuclei. There were no Touton's giant cells seen to suggest the diagnosis of xanthogranuloma. The final pathology diagnosis was orbital xanthoma (Figure 5).

Figure 1
figure 1

A 38-year-old Bangladeshi labourer with right eye ptosis and proptosis.

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Figure 2
figure 2

A CT coronal scan of the orbit revealed a mass at the right eye superior rectus and levator superioris complex.

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Figure 3
figure 3

A MRI coronal scan of the orbit showed the mass to be distinct from the right superior rectus and appear to involve only the right levator superioris.

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Figure 4
figure 4

An open biopsy through the skin crease of the right eye revealed an uncapsulated orange coloured lesion between the orbicularis oculi and the orbital septum with infiltration of the levator aponeurosis.

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Figure 5
figure 5

Histology slide showing orbital xanthoma.

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Comment

Xanthoma occurring within the orbit is extremely rare. There have been only a few reports in the literature.1, 2, 3 They are typically found in the subcutaneous tissues usually along the Achilles tendon and extensor tendons of the hand of patients with hyperlipidaemia. They are believed to develop as a result of leakage of lipids from the blood vessels into the surrounding tissue. The lipids were subsequently phagocytosed by macrophages. As the cholesterol is not degraded, the macrophages have foamy cytoplasm. Extracellular cholesterol can induce chronic inflammatory reaction which may account for the dull ache experienced by our patient. Giant cells similar to that seen in chalazion may occur in response to the inflammation and fibrosis may develop. The condition needs to be differentiated from two other conditions: xanthogranuloma and necrobiosis xanthoma. In the former, Touton's cells are found histologically and in the later the blood tests show dysproteinaemia.

On the CT and MRI scans, xanthoma could not be differentiated from other orbital benign tumours such as frontal mucocele, epidermoid cyst, dermoid cyst, haemangioma, meningioma, Langerhans cell histiocytoma, and fibrous dysplasia.4 In cases of chronic inflammation, the clinical features may be confused with pseudotumour leading to unnecessary investigations for autoimmune diseases. Biopsy is the only certain mean of diagnosing orbital xanthoma.

In summary, as orbital xanthoma cannot be diagnosed with certainty either clinically or by radiological imaginations, this unusual condition should be included in the differential diagnosis of proptosis in patients with eyelid xanthelasma or hyperlipidaemia.