RFC1 and mild neurocognitive disorder: This is particularly relevant, considering that the etiology of sporadic MND such as amyotrophic lateral sclerosis (ALS) and primary lateral sclerosis (PLS) remains unexplained in up to ~ 90% of cases, and biallelic repeat expansions in RFC1, an autosomal-recessive disease, may potentially offer an additional genetic explanation in at least a subset of those patients [16–18].