Retinitis pigmentosa

Published on 02/04/2015 by admin

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Last modified 22/04/2025

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207 Retinitis pigmentosa

Instruction

Examine this patient’s fundus.

Examine this patient’s eyes.

Salient features

History

• Family history of blindness (can be autosomal recessive, which is more severe, or autosomal dominant, which is more benign)

• Decreased nocturnal vision

• Altered colour vision

• Loss of peripheral vision

• Blurry vision.

Examination

• Peripheral retina shows perivascular ‘bone spicule pigmentation’ and arteriolar narrowing (Fig. 207.1). The retinal veins (never the arteries) often have a sheath of pigmentation for part of their course. The pigment spots that lie near the retinal veins are seen to be anterior to them, and so they hide the course of the vessel. (In this respect, they differ from the pigment around the spots of choroidal atrophy in which the retinal vessels can be traced over the spots.)

• Optic disc is pale

• Maculopathy which is atrophic or cystoid.

Fig. 207.1 Retinitis pigmentosa.

Proceed as follows:

• Look for polydactyly in the hands and feet (Laurence–Moon–Biedl syndrome)

• Comment on the white walking aid (if any) used by the registered blind

• Tell the examiner that you would like to check visual fields.

Diagnosis

This patient is obese, has polydactyly and retinitis pigmentosa (lesion) caused by Laurence–Moon–Biedl syndrome (aetiology) and is registered blind (functional status).

Questions

What is the prognosis in retinitis pigmentosa?

Most patients are registered blind by the age of 40 years, with central field <20 degrees in diameter. Almost all patients lose central vision by the seventh decade.

What do you know about retinitis pigmentosa?

Retinitis pigmentosa is a slow degenerative disease of the retina. It occurs in both eyes, begins in early childhood, and often results in the loss of sight by middle or advanced age. The degeneration primarily affects the rods and cones, in particular the rods. Rods mediate achromatic vision in starlight or moonlight whereas cones are important for colour vision and fine acuity in daylight.

How may retinitis pigmentosa present?

It may present with defective vision at dusk (night blindness), which may occur several years before the pigment is visible in the retina.

Advanced-level questions

Mention a few systemic disorders associated with retinitis pigmentosa

• Laurence–Moon–Biedl–Bardet syndrome, which is a recessively inherited disorder characterized by mental disability, polydactyly, syndactyly, hypogonadism, obesity and renal disease (structural abnormalities such as calyceal cysts or calyceal clubbing and blunting).

• Bassen–Konzweig syndrome (abetalipoproteinaemia), characterized by fat malabsorption, abetalipoproteinaemia, acanthocytosis and spinocerebellar ataxia (Ophthalmology 1984;91:991).

• Refsum’s disease (phytanic acid storage disease), an autosomal recessive disorder characterized by hypertrophic peripheral neuropathy, deafness, ichthyosis, cerebellar ataxia, raised CSF protein levels in the absence of pleocytosis.

• Kearns–Sayre syndrome, a triad of retinitis pigmentosa, progressive external ophthalmoplegia and heart block (Br J Ophthalmol 1985;69:63).

• Usher’s disease, a recessively inherited disorder characterized by congenital, non-progressive, sensorineural deafness (Arch Ophthalmol 1983;101:1367).

• Friedreich’s ataxia (p. 267).

What do you know about the genetics of retinitis pigmentosa?

More than 45 genes for retinitis pigmentosa have been described. These genes account for only about 60% of all patients; the remainder have defects in as yet unidentified genes. Exceptions being the:

• RHO, gene for rhodopsin gene, which leads to about 25% of dominant retinitis pigmentosa

• USH2A, which might cause about 20% of recessive disease (including many with Usher syndrome type II)

• RPGR, which accounts for about 70% of X-linked retinitis pigmentosa.

Mutations in RHO, USH2A, and RPGR cause about 30% of all cases of retinitis pigmentosa in aggregrate.

Which ocular conditions are associated with retinitis pigmentosa?

• Open-angle glaucoma

• Posterior subcapsular cataracts

• Keratoconus.

What is secondary retinitis pigmentosa?

Secondary retinitis pigmentosa is a sequela to inflammatory retinitis. It is often ophthalmoscopically indistinguishable from the primary condition, the electroretinographic and electro-oculographic responses are slightly subnormal unless the condition is far advanced. (In the primary type, the electroretinograph and electro-oculograph responses are markedly subnormal.)

What is retinitis pigmentosa sine pigmento?

A variety of retinitis pigmentosa but without visible pigmentation of the retina.

What is inverse retinitis pigmentosa?

Bone corpuscles are visible in the perifoveal area, whereas the retinal periphery is normal.

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