Intriguingly, trinucleotide repeat expansion in the ATXN2 gene is also a risk factor for amyotrophic lateral sclerosis (ALS), a neurodegenerative disease of upper and lower motor neurons, but this association is only seen for repeats of intermediate size, below the range usually associated with spinocerebellar ataxia (34 repeats or more) but above the normal range (Elden et al., 2010). Here, ATXN2 is linked to amyotrophic lateral sclerosis.