Clinical Guidance
Spinocerebellar ataxia type 7 (SCA7) comprises a phenotypic spectrum ranging from adolescent- or adult-onset progressive cerebellar ataxia and cone-rod retinal dystrophy with progressive central visual loss to infantile or early-childhood onset with multiorgan failure, an accelerated course, and early death . One important aspect of SCA7 clinical manifestations is their extreme variability with respect to age of onset and rate of progression. Affected individuals may present in infancy, childhood, adolescence, young adulthood, middle age, or old age. When onset is at or before adolescence, initial manifestations are typically impaired vision, ultimately progressing to blindness from retinal degeneration. Individuals with manifestations in their teens may be blind within a decade or less. In adults, the progressive cerebellar ataxia (i.e., dysmetria, dysdiadochokinesia, and poor coordination) usually precedes the onset of visual manifestations. The age of onset inversely correlates with rate of progression and extent of symptomatology, as onset in or after the fifth decade of life gives a predominant cerebellar ataxia without progression to significant visual impairment, whereas onset prior to middle age often features progression to vision loss. Progression to severe disability resulting in death varies based on age of onset, ranging from months in infants to fewer than ten years in older children to two to three decades in adolescents and adults. While the rate of progression varies, the eventual result for almost all affected individuals is severe dysarthria, dysphagia, and a bedridden state with loss of motor control. To date, more than 1,000 individuals with SCA7 have been identified worldwide. Frequency of select features in adolescent- or adult-onset disease are summarized in . Adolescent- or Adult-Onset SCA7 Table 2. Select Features of Adolescent- or Adult-Onset SCA7
