C9orf72 and frontotemporal dementia: As would be expected, post-hoc analysis showed that duration of illness was significantly less in C9ORF72 cases with MND than C9ORF72 associated FTD (p = 0.014), but not less than C9ORF72 associated FTD + MND (p = 0.281), nor was there any difference in disease duration between C9ORF72 associated FTD and C9ORF72 associated FTD + MND (p = 0.815).