Spinocerebellar Ataxia-Type 7
Spinocerebellar ataxia-type 7 (SCA7) is a progressive autosomal dominant neurodegenerative disorder characterized by cerebellar ataxia associated with progressive macular dystrophy. The disease primarily affects the cerebellum and retina and is caused by expansion of an unstable trinucleotide CAG repeat on chromosome 3 which encodes a polyglutamine tract in the corresponding protein, ataxin-7. Pathological alleles contain from 36 to 306 CAG repeats. The clinical hallmark of SCA7 is the association of hereditary ataxia together with progressive visual loss caused by pigmentary macular degeneration. This association represents a distinct disease entity originally classified as an autosomal dominant cerebellar ataxia type II by Anita Harding.
KeywordsCerebellar Ataxia Polyglutamine Tract Clinical Hallmark Hereditary Ataxia Distinct Disease Entity
Clip 1: examination of the index patient shows mild cerebellar dysfunction with slight finger-nose ataxia, normal rapid alternating movements, a mildly wide-based gait, and difficulty with tandem gait. Clip 2: examination of the index patient’s nearly blind son shows ophthalmoplegia in all directions of gaze with difficulty generating saccadic and pursuit eye movements. Rapid alternating hand movements are slow, and severe finger-nose ataxia is present which appears at least in part due to poor vision. There was severe truncal and gait ataxia requiring assistance with walking.
SCA type 7.mp4 (MP4 65,548KB)