GRN and frontotemporal dementia: In contrast, patients with frontotemporal dementia (also called frontotemporal lobar degeneration, FTLD) exhibit clinical and pathological characteristics that differ from AD, and most of the autosomal dominantly inherited familial forms of FTLD are caused by a mutation in the MAPT/Tau gene, by a mutation in the progranulin (PRGN) gene, or by a triplet repeat expansion in the C9ORF72 gene, all three of which carry out vastly different normal functions in the cell and are also unrelated to the genes mutated in FAD (Rademakers et al., 2012).