Primary nonfamilial ocular amyloidosis

Main

Sir,

Ocular amyloidosis is a rare cause of vitreous haze1,2 and should be included in the differential diagnosis of vitreous opacification. The ophthalmologist should be aware that ocular amyloidosis may occur sporadically and that vitreous biopsy with specific staining with Congo red dye may be indicated.

Case history

A 62-year-old female presented with a 2-year history of floaters in her left eye. Visual acuity was ‘counting fingers’ in the left eye and 6/6 in the right. Anterior segment examination and pupil reactions were both normal. In the left vitreous there were dense opacities obscuring the retina (Figure 1a), while in the right eye the only abnormality noted was a patch of vitreous condensation overlying the inferior arcuate vessels (Figure 1b). Medical history and examination was unremarkable and there was no significant family history. Serum angiotensin converting enzyme levels, syphilis serology and immunological investigations for HLA B27 markers and autoantibodies were normal. An ultrasound scan of the left eye showed that the retina was flat and there were no intraocular masses. A vitrectomy with vitreous biopsy was performed. The specimen was stained with haematoxylin and eosin and reported to show no signs of malignancy or infection. Postoperatively the left retina appeared to be normal and the visual acuity improved to 6/6.

Figure 1
figure1

(a) Dense vitreous opacities in the left eye. (b) Vitreous condensations overlying inferior arcuate vessels. (c) Characteristic apple-green fluorescence of the vitreous when viewed through crossed polarising lenses (magnification ×200). (d) Apple-green fluorescence of amyloid deposits in the iris specimen (magnification ×100).

A year after surgery the visual acuity had deteriorated to 6/18 in both eyes. Vitreous opacities had recurred in the left eye and similar opacities were apparent in the right. A right vitrectomy and vitreous biopsy were performed, with the cytology specimen being specifically stained with Congo red dye for amyloid (Figure 1c). A diagnosis of amyloidosis of the vitreous was confirmed. A full history and examination failed to identify any evidence of systemic amyloidosis. There was no family history of amyloidosis.

The original vitreous sample from the left eye was re-examined using immunohistochemistry techniques and stained with Congo red dye; these confirmed the presence of amyloid.

At a routine check-up 3 years later, the right eye was found to have an intraocular pressure of 50 mmHg. It was unresponsive to medical therapy and a trabeculectomy was carried out. Amyloid deposits were found in the biopsy specimens of conjunctiva and iris (Figure 1d).

Comment

Amyloid is the name given to a group of proteins that have a characteristic beta-pleated structure and emit an apple-green fluorescence in polarised light when stained with Congo red dye.1,2 Amyloidosis is the term used to cover a group of disorders characterised by the extracellular deposition of amyloid in the tissues of the body,2 in sufficient quantity to compromise function.1 It may affect multiple organs (systemic) and can have a family pedigree (familial).1 The underlying cause may be unknown (primary) although amyloid can develop as a consequence of chronic inflammatory or neoplastic conditions (secondary amyloidosis).1,2,3

Amyloid deposits in the vitreous are known to occur in the systemic familial amyloidoses; however, isolated vitreous deposits in the absence of a family history (primary nonfamilial amyloidosis of the vitreous) are extremely rare.3,4 It may mimic a wide range of ocular conditions including vitritis, lymphoma, endophthalmitis and an old vitreous haemorrhage.5,6

Diagnosis relies upon clinical suspicion and the specific staining of biopsy specimens with Congo red dye (Figure 1c, d.

The earliest changes seen in ocular amyloidosis are small pinpoint opacities overlying retinal blood vessels (Figure 1b), which are easily overlooked or dismissed as vitreous condensations. Over time these enlarge and infiltrate the vitreous, producing characteristic glass-wool-like sheets and globular opacities (Figure 1).5,6

Glaucoma occurring in association with vitreous amyloidosis is thought to result from transport of amyloid by the aqueous fluid and deposition in the trabecular meshwork.2,3,7,8

At present there is no medical therapy for ocular amyloidosis, and vitrectomy is the treatment of choice for the vitreous opacification.2,3,4,7 However, as we have demonstrated, even after vitrectomy, amyloid may infiltrate the trabecular meshwork and iris, resulting in secondary glaucoma.

The ophthalmologist should be aware that ocular amyloidosis may present with a vitreous haze and should be included in the differential diagnosis of vitreous opacification. A full medical and family history is mandatory but may be negative in the case of sporadic ocular amyloidosis. When a vitreous biopsy is considered the sample should be stained specifically for amyloid. Long-term follow-up of patients with proven ocular amyloidosis is mandatory as glaucoma may develop insidiously as a late complication.

References

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Correspondence to C M Knapp.

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