A separate analysis considering the age of onset of FTD or ALS led to the same trend of correlation in HTT (r = −0.16, P = 0.033 for FTD; r = −0.24, P = 0.049 for ALS) conversely to the ATXN3 locus for which the correlation coefficients were not significant when considering the two phenotypes separately. This evidence concerns the gene ATXN3 and frontotemporal dementia.