In addition, although the A239T tau variant is reported to be benign (59,60), a recent study identified this mutation in a patient carrying a repeat expansion in the C9ORF72 gene (61), which is the most common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) (62,63). Here, C9orf72 is linked to frontotemporal dementia.