GRN and primary progressive aphasia: In GRN null mutation carriers it has been demonstrated that the shortage of progranulin (i) invariably precedes clinical symptoms, since a reduction of protein is also measured in pre-symptomatic subjects (ii) is associated with multiple clinical presentations ranging from behavioral variant of frontotemporal dementia (bvFTD) (the most common clinical presentation), to primary progressive aphasia, corticobasal syndrome, AD, Parkinson's disease or dementia with Lewy bodies phenotype (Le Ber et al., 2008; Benussi et al., 2009; Arosio et al., 2013; Wauters et al., 2017).