Spinocerebellar ataxia type 7 with RP1L1-negative occult macular dystrophy as retinal manifestation

Background: Spinocerebellar ataxia Type 7 (SCA7) is an autosomal dominant, progressive neurodegenerative disorder, primarily characterized by cerebellar ataxia. The disease is caused by the expansion of a CAG trinucleotide repeat within the ataxin-7 gene when its CAG repeat sequences are extended beyond 38. The degree of retinopathy can vary from pigment change in the fovea to foveal atrophy and is correlated with the number of CAG repeats. The present study describes a case of SCA7 with a retinal presentation similar to occult macular dystrophy (OMD) which is an inherited macular dystrophy characterized by presenting with a normal fundus and fluorescein angiography but with progressive central visual loss. Materials and Methods: Report of a case. Results: In this case, no specific abnormality was found on fundus examination, fluorescein angiography, full-field electroretinography and infrared autofluorescence. Spectral-domain optical coherence tomography showed foveal thinning, focal disruption of the ellipsoid zone, and central loss of the outer segment-retinal pigment epithelium interdigitation zone that were well matched with the multifocal electroretinography finding. Thirty-nine CAG repeats in ataxin-7 gene were identified through genetic testing. Conclusions: SCA7 can present with a very mild form of retinal degeneration similar to the classic phenotype of RP1L1-negative OMD in case of the lower number of CAG repeats.