ATXN2 and Parkinson disease: Intermediate size polyglutamine expansions within ATXN2 were more recently implicated as risk factor of the motor neuron disease amyotrophic lateral sclerosis (ALS), of the basal ganglia tauopathy progressive supranuclear palsy (PSP) and of the preferential midbrain degeneration in Parkinson’s disease (PD) [4–7].