C9orf72 and Parkinson disease: Therefore, although the abnormal repeats of C9orf72 gene account for 23–47% of familial FTD with or without ALS and 4–20% of sporadic ALS (2, 21, 26), our observation combined with previous findings suggest that variation in the C9orf72 does not play a major role in the susceptibility to the wider spectrum of Parkinsonism and dementia syndromes.