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Joshua Levinson, Suma P Shankar, Scott R Lambert, Jiong Yan; Retinal Findings in a Family with Spinocerebellar Ataxia Type 7. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3836. doi: https://doi.org/.
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Spinocerebellar ataxia type 7 (SCA7) is an autosomal dominant cerebellar ataxia (ADCA) due to polyglutamine-expansion in Ataxin-7. It is unique among the ADCAs for its association with retinal degeneration and vision loss. We describe the spectrum of retinal pathology seen in a family with SCA7.
Retrospective chart review including fundus photography, optical coherence tomography, electroretinography, visual fields, and fundus autofluorescence of three family members with SCA7.
The proband, Patient 1 (Mother) presented at age 26 with Light Perception vision. Initial examination was significant for optic disc pallor, vascular attenuation and central macular atrophy. Two years later, her vision had declined to No Light Perception and fundus exam demonstrated marked progression of central macular atrophy and peripheral bone spicule formation. Seven years after the onset of vision loss, neurologic exam demonstrated ataxia, dysarthria, and slowed saccades. Family history revealed vision loss and ataxia in multiple relatives. Genetic testing of Ataxin-7 identified heterozygous 61 CAG trinucleotide repeat expansion confirming the diagnosis of SCA7. Patient 2 (Son) presented at age 11 with visual acuity of 20/300 bilaterally and decreased color vision. Fundoscopic exam was notable for optic nerve pallor, vascular attenuation and peripheral pigmentary changes. ERG testing demonstrated diminished rod and cone function, and Goldmann visual field testing showed paracentral scotoma. Patient 3 (Daughter) presented at age 14 with visual acuity of 20/50 bilaterally and minimal fundoscopic changes. Her neurologic exam was unremarkable. The only significant ophthalmic finding was thinning of the subfoveal ellipsoid zone bilaterally on OCT. Early cerebellar volume loss was noted on MRI. Image 2 contains clinical images for patients 1-3.
SCA7 is an autosomal dominant disorder associated with retinal and cerebellar degeneration. Vision loss is due to development of a progressive cone-rod dystrophy. Initial findings may be subtle, and ancillary testing can assist with early diagnosis.
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