C9orf72 and mild neurocognitive disorder: An intronic hexanucleotide repeat expansion (GGGGCC) in the gene chromosome 9 open reading frame 72 (C9orf72) is one of the most frequent genetic alterations causative for neurodegenerative disease and the most common genetic cause of frontotemporal lobar degeneration (FTLD) and motor neuron disease (MND) [1].