Moreover, SV2A PET has also been used in frontotemporal dementia (FTD), which is thought to exist on a disease spectrum with ALS, to study synaptic density changes in patients with behavioral variant FTD (Malpetti et al., 2023), and in carriers of a repeat expansion in the chromosome 9 open reading frame 72 (C9ORF72) gene, which has been linked to both ALS and FTD (Malpetti et al., 2021). This evidence concerns the gene C9orf72 and amyotrophic lateral sclerosis.