For example, nonfluent/agrammatic PPA may be caused by either FTLD-tau or FTLD-TDP (Grossman, 2010; Rusina et al., 2022), while a single pathology such as AD can manifest through multiple phenotypes, most often the lvPPA but occasionally others (Mesulam et al., 2014a; Mesulam et al., 2014b). This evidence concerns the gene MAPT and Alzheimer disease.