Case of the Month I February 2020

Case of the Month
February 27, 2020

The Case

The patient was a 61-year-old white woman with longstanding decreased vision in both eyes and no recent significant change in vision. Her visual acuity was 20/50 OD and 20/80 OS. Her anterior segment examination was remarkable for a mild cataract in each eye. The posterior segment examination was remarkable for large areas of atrophy in the maculas and peripheries of both eyes and pigment mottling elsewhere. The vitreous was quiet and there was no significant macular edema in either eye. What is the most likely diagnosis? What treatment, if any, would you recommend?

The fundus photographs show severe atrophic changes and some pigment mottling in areas of intact retina in both eyes. The fluorescein angiogram shows corresponding areas of severe atrophy of the retina, retinal pigment epithelium, and choriocapillaris of both eyes. There is no disc or macular leakage. Autofluorescence shows hypoautofluorescence of the atrophic areas and there is mild hyperautofluorescence at the borders of the atrophic areas, indicating stressed RPE. The OCTs show retinal atrophy, and the areas that are not totally atrophic have loss of the ellipsoid zones and disruption of the interdigitation zones with intact outer limiting membranes.

Genetic testing was ordered, and she was found to be heterozygous with a c.654del mutation of the PRPH2 gene (previously known as RDS). This gene codes for peripherin 2, which is found in rods and cones and is an adhesion molecule involved in stabilization and compaction of the outer segment discs. There was no edema contributing to visual loss that might have responded to carbonic anhydrase inhibitor treatment (e.g., acetazolamide). No genetic treatment is currently available, but it is possible that in the future Cas9-mediated allelic exchange repair might prevent transmission of this and other heterozygous conditions to offspring
(see https://www.ncbi.nlm.nih.gov/pubmed/30102296).

Case Photos

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The fundus photographs show severe atrophic changes and some pigment mottling in areas of intact retina in both eyes. The fluorescein angiogram shows corresponding areas of severe atrophy of the retina, retinal pigment epithelium, and choriocapillaris of both eyes. There is no disc or macular leakage. Autofluorescence shows hypoautofluorescence of the atrophic areas and there is mild hyperautofluorescence at the borders of the atrophic areas, indicating stressed RPE. The OCTs show retinal atrophy, and the areas that are not totally atrophic have loss of the ellipsoid zones and disruption of the interdigitation zones with intact outer limiting membranes.

Genetic testing was ordered, and she was found to be heterozygous with a c.654del mutation of the PRPH2 gene (previously known as RDS). This gene codes for peripherin 2, which is found in rods and cones and is an adhesion molecule involved in stabilization and compaction of the outer segment discs. There was no edema contributing to visual loss that might have responded to carbonic anhydrase inhibitor treatment (e.g., acetazolamide). No genetic treatment is currently available, but it is possible that in the future Cas9-mediated allelic exchange repair might prevent transmission of this and other heterozygous conditions to offspring
(see https://www.ncbi.nlm.nih.gov/pubmed/30102296).

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