GRN and Alzheimer disease: It will be important to conduct further group and detailed single case studies in patients with GRN-associated PPA to define the full clinico-pathological and clinico-genetic spectrum of the disorder, to establish the extent to which GRN-associated PPA, AD-LPA and other non-fluent cases can be distinguished on neuropsychological grounds, and to address in detail the anatomical and pathophysiological basis of the GRN-associated language ‘network-opathy’.