C9orf72 and frontotemporal dementia: Pathogenic NOTCH2NLC expansions have been identified in patients with essential tremor (ETM6, MIM #618866), C9ORF72-associated amyotrophic lateral sclerosis/frontal temporal dementia (ALS/FTD) (Tian et al., 2019; Jiao et al., 2020), Parkinsonism (Ma et al., 2020), and multiple system atrophy (Fang et al., 2020).