GRN and frontotemporal dementia: Importantly, a recent study however has reported six patients carrying homozygous GRN mutations with divergent phenotypes and variable ages of onset, including some presenting classical CLN11 symptoms at early age of onset and others showing a distinct delayed phenotype of frontotemporal dementia after 40 or 50 years, suggesting that CLN11 and FTLD-TDP are extreme phenotypes of a common spectrum of disorders caused by biallelic GRN mutations [28] (Fig. 1a).