GRN and Alzheimer disease: The aphasic disorder associated with GRN mutations seems nevertheless to be distinct from the avPPA with apraxia of speech observed occasionally in patients with FTLD-tau (Rohrer et al., 2010a,c), or from the logopenic variant of PPA (lvPPA), commonly associated with an atypical presentation of AD pathology (Gorno-Tempini et al., 2011; Rohrer et al., 2012).