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enhanced S-cone syndrome
Enhanced S-cone syndrome, sometimes called Goldman-Favre syndrome, is a retinal disorder characterized by increased sensitivity to blue light, night blindness from an early age, and decreased vision. Additional features include an optically empty liquefied vitreous, progressive foveal or peripheral retinoschisis, macular cysts, chorioretinal atrophy and pigmentary retinopathy as well as posterior subcapsular cataract formation. Enhanced S-cone syndrome is the only retinal disorder that has a gain of a subtype of photoreceptors, in this case the S-cones (short wave length) that detect blue light are increased in number. Rod photoreceptors and red and green cone receptors are degenerated to a variable degree. Electroretinography shows an extinct rod photoreceptor response and hypersensitivity to shorter wavelengths.
There is considerable variation in the clinical features of NR2E3 mutations which has led to some confusion in the nosology. Some cases are called juvenile retinoschisis, others are called retinitis pigmentosa, or clumped pigment retinopathy. Central acuity ranges from near normal (20/40) in young people to 20/200 or worse especially in older adults. Visual field constriction likewise varies from patient to patient. Retinal pigmentary changes and the amount of cystic changes in the macula are somewhat age dependent.
No general systemic manifestations are associated with enhanced S-cone syndrome and Goldman-Favre syndrome.
This is an autosomal recessive retinal disorder caused by mutations in NR2E3, also called the photoreceptor-specific nuclear receptor, PNR, located on chromosome 15q23. It is a part of a transcription factor complex necessary for the development of photoreceptors. Mutations in NR2E3 cause degeneration of rod photoreceptors and an increased number of S-cone photoreceptors resulting in an increased ratio of blue to red-green cone photoreceptors. Mutations in the NR2E3 gene can also cause a clinical picture resembling simple autosomal recessive retinitis pigmentosa.
Two brothers with an enhanced S-cone phenotype and normal rod function have been reported. Scotopic b-wave ERG amplitudes were normal but OCT showed flattening of the mcaular area and thinning of the photoreceptor layer. This may be the result of a different mutation in this family but no molecular defect was found.
There is presently no effective treatment for the disorder, but visual function can be improved with low vision aids. Cataract surgery may be beneficial.