Cone Rod Dystrophy

This 22YO male medical student gave a history of relatively rapid bilateral central vision loss 6 years earlier. His symptoms have been stable since, and he continues to function well visually, personally, and academically.

Color imaging shows a bullseye of pigmentary loss around each fovea. The area of pigment loss is hypo-autofluorescent. OCT scanning shows central outer retinal atrophy, particularly in the perifovea. The changes are markedly symmetrical between the eyes.

Genetic testing revealed two pathogenic ABCA4 mutations.

Learning Points:
Cone-rod dystrophy is a group of inherited retinal disorders characterized by loss of cone photoreceptors followed by rod photoreceptors. Symptoms include decreased visual acuity, central vision loss, color vision abnormalities, and photophobia.

Several genes have been implicated, including ABCA4, CRX, GUCY2D, and RPGR. ABCA4 mutations are found in autosomal recessive cone-rod dystrophy and Stargardt disease.

For an excellent review of the complex clinical and genetic spectrum of ABCA4 disorders, see Cremers et al, Progress Retinal Eye Research 2020;79;100861.

This 42YO female presented with counting fingers vision OD and 20-25 vision OS. There was no family history of vision loss.

A bull’s-eye pattern of perifoveal atrophy was noted on Optos color and fundus autofluorescence imaging, with loss of photoreceptors on OCT. The outer retinal atrophy extended through the macular center in her right eye, accounting for the counting-fingers vision.

Learning Points:
Cone-rod dystrophy is a group of inherited retinal disorders characterized by loss of cone photoreceptors followed by rod photoreceptors. Symptoms include decreased visual acuity, central vision loss, color vision abnormalities, and photophobia.

Several genes have been implicated, including ABCA4, CRX, GUCY2D, and RPGR. ABCA4 mutations are found in autosomal recessive cone-rod dystrophy as well as Stargardt Disease.