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Editor,—Usher’s syndrome is an autosomal recessive condition characterised by retinitis pigmentosa and hearing loss. It is the most common cause of combined blindness and deafness in the USA. Usher’s syndrome has two well defined subtypes including type I and type II.1 Type I has more severe and early onset findings.
A 59 year old woman with retinitis pigmentosa and type I Usher’s syndrome developed blurred vision in the left eye over a 4 month period. The best corrected visual acuity was 20/50 in the right eye and 20/80 in the left eye. Anterior segment examination and intraocular pressures (16 mm Hg) were normal bilaterally. Ophthalmoscopic examination showed mild optic disc pallor, marked vascular attenuation, and retinal pigmentary changes in both eyes. Inferotemporally in the left eye, there was a 15 × 10 mm dome-shaped choroidal melanoma with a secondary retinal detachment affecting the inferior half of the fundus (Fig 1). There was no evidence of retinal invasion or seeding. A-scan and B-scan ultrasonography demonstrated a 5.0 mm thick choroidal mass with low to medium internal reflectivity, acoustic hollowness, and a secondary retinal detachment (Fig 2). Goldmann perimetry showed marked constriction of visual fields with only 5 degrees of central field remaining in both eyes. Electroretinographic testing under photopic and scotopic conditions revealed that the b-wave was isoelectric.
The patient was treated with iodine-125 plaque radiotherapy with tumour apex dose of 9000 cGy, base dose of 43 000 cGy, and optic disc dose of 3700 cGy. The tumour showed a satisfactory response to radiation. At 10 months’ follow up, the subretinal fluid dried up completely but radiation papillopathy developed. The papillopathy resolved over 5 months, leaving more optic disc pallor. At 22 months’ follow up, the patient underwent cataract surgery with posterior chamber lens implantation in both eyes because of advanced posterior subcapsular cataract. At 40 months’ follow up, the vision was hand movements in the right eye and tumour thickness was 2.8 mm. There was no radiation retinopathy or metastatic disease.
Abnormalities involving chromosomes 1 (type II), 11, and 14 (type I) have been observed in patients with Usher’s syndrome.1Reported chromosome alterations in uveal melanoma involve chromosomes 3, 6, 8, and 92; therefore, the simultaneous occurrence of these two conditions, as in our patient, is probably coincidental.
The development of retinal detachment in a patient with retinitis pigmentosa is rare because of adhesions between the retinal pigment and sensory epithelium. Only a few cases of retinitis pigmentosa with retinal detachment have been reported.3 Our patient illustrates a non-rhegmatogenous retinal detachment with retinitis pigmentosa.
Our patient developed radiation papillopathy with an optic disc dose less than 5000 cGy, which is unusual.4 The atrophy/gliosis of the optic disc in retinitis pigmentosa might increase the susceptibility of the disc to irradiation. On the other hand, she did not develop radiation retinopathy despite a high dose of radiation to the retina. Perhaps the atrophic retina in retinitis pigmentosa was unable to elicit a radiation response.
Choroidal melanoma can rarely lead to a pseudoretinitis pigmentosa picture secondary to retinal invasion and dispersion of melanoma cells on the retina.5 Retinal invasion was not present in our patient and retinal pigmentary changes were noted in both eyes, ruling out pseudoretinitis pigmentosa.
Retinitis pigmentosa can be associated with several fundus tumours including giant drusen resembling astrocytoma and acquired vasoproliferative tumours.6 To our knowledge, this is the first report of choroidal melanoma in a patient with retinitis pigmentosa.
Supported by the Paul Kayser International Award of Merit in Retina Research, Houston, TX (J Shields) and Eye Tumor Research Foundation, Philadelphia, PA, USA
The authors wish to thank Dr Andy Hay for referring the patient.
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