Bilateral exudative retinopathy as the initial manifestation of retinitis pigmentosa

A Coats'-like retinopathy affects approximately 1–4% of cases of longstanding retinitis pigmentosa (RP).^1,2 As a presenting sign of RP, however, Coats'-like retinopathy is extremely rare.³ We present a case of bilateral exudative retinopathy suggestive of Coats' disease in a 12 year old boy in whom investigation revealed previously undiagnosed RP.

Case report

A 12 year old male presented with a 3 week history of blurred vision in both eyes. There was no significant medical or family history. Visual acuities were 6/120 in the right eye and 6/15 in the left eye. Anterior segment examination was normal. The posterior segment of both eyes showed extensive subretinal exudation, serous retinal detachment, and overlying retinal telangiectasia (Fig 1A). There was cystoid macular oedema with a lamellar macular hole in the left eye. The optic discs appeared normal. Additionally, mottled granularity of the retinal pigment epithelium (RPE) was noted in the mid-periphery of both retinas (Fig 1B). Upon further questioning, he admitted to night blindness.

Figure 1.

(A) Fundus photograph of the right eye showing subretinal exudation, serous retinal detachment, and telangiectatic retinal vessels. (B) Fundus photograph of the left eye showing mottled granularity of the retinal pigment epithelium.

A fluorescein angiogram confirmed retinal telangiectasia, serous retinal detachment, and macular oedema (Fig 2A). An electroretinogram (ERG) showed an isoelectric response under both scotopic and photopic conditions (Fig 2B). Visual field testing revealed marked constriction in both eyes.

Figure 2.

(A) Fluorescein angiogram of the right eye showing retinal ischaemia with adjacent telangiectasia. (B) Scotopic electroretinogram showing isoelectric response in both eyes.

A diagnosis of retinal telangiectasia, exudative retinopathy, and retinitis pigmentosa was made and the areas of most severe telangiectasia were treated with retinal cryotherapy. One year later the retinal telangiectasia had mostly resolved, the exudation was slightly less extensive and the visual acuity was unchanged.

Comment

The association between retinitis pigmentosa and exudative retinopathy was first described in 1956⁴ and has been termed a “Coats'-like RP.”⁵ Various studies have suggested that 1–4% of RP cases will show such a response.^1,2 This entity differs from true Coats' disease in that Coats'-like RP often occurs bilaterally, has no sex predisposition, and shows diffuse pigmented alterations in both fundi.^5,6 The cause is unknown but it may represent a vasodilatory response to toxic products of photoreceptor/RPE degeneration.² Our case is unusual in that almost all previous reported cases have occurred in the setting of longstanding RP.^2,3 Our patient had never consulted an ophthalmologist despite being night blind and having markedly constricted visual fields. We recommend that ophthalmologists consider an underlying diagnosis of retinitis pigmentosa in any patient presenting a picture of bilateral exudative retinopathy.