C9orf72 and Parkinson disease: Up to 35% of patients with the C9orf72 gene expansion have parkinsonism (6) and 7% of patients with PSP syndrome, and a positive family history carries the C9orf72 gene expansion, representing the second-most frequent genetic mutation related to GPSPS after MAPT. For those patients with >30 repeats and PSP syndrome, the mean age at presentation was 64 years (range 40–79), and 12% of patients had a family history of neurodegenerative disease.