C9orf72 and Parkinson disease: The C9orf72 expansion of a hexanucleotide GGGGCC repeat encoding dipeptide repeats exhibits variable phenotypic expressivity; individuals can develop MND and FTD (or both), and there are also associations between C9orf72 and parkinsonism, psychosis, and Huntington’s disease (HD) like phenotypes [24, 25].