Alternatively, the lack of decline over time in all 3 disease stages raises the intriguing possibility that these deficits are not merely preclinical signs of FTD as a result of early neurodegeneration, but might be indicative of a neurodevelopmental disorder in C9orf72, which at a certain age is superimposed by additional neurodegeneration. This evidence concerns the gene C9orf72 and frontotemporal dementia.