Spinocerebellar Ataxia Type I

Question 1

____ is an inherited progressive neurodegenerative disorder characterised by ataxia, dysarthria & progressive bulbar dysfunction.

Answer 1

Spinocerebellar ataxia type 1 (SCA1)

Question 2

SCA1 is inherited as an autosomal dominant trait due to unstable length mutations in a ____ within the coding sequence of the gene ____ at 6p23.

Answer 2

CAG polyglutamine repeat; ATXN1

Question 3

The onset of SCA1is usually in the third or fourth decade w/ progressive ____ & ____.

Answer 3

cerebellar ataxia; spastic paraparesis.

Question 4

Normal individuals show a stable inheritance of ____, whereas in affected patients with SCA1, the repeat length is expanded to ____ and is unstable, w/ a strong tendency for further expansion at paternal transmission.

Answer 4

19 – 36 repeats; 42 – 81 units

Question 5

____ is the commonest form of SCA but at least ____ other variants w/ autosomal dominant inheritance are known.

Answer 5

Type I; 27

Question 6

T/F. The size of the repeat is inversely correlated to the age of onset (i.e. earlier onset w/ larger repeats).

Answer 6

True.