APP and primary progressive aphasia: Among the known genetic markers, presenilin 1 (PSEN1)/PSEN2 and amyloid precursor protein (APP) variants can be observed in cases with lv-PPA, while chromosome 9 open reading frame 72 (C9orf72), microtubule-associated protein tau (MAPT), and some progranulin (GRN) mutations have been reported in non-fluent/agrammatic variant (nfv-)PPA cases, and GRN/TAR DNA-binding protein of 43 kDa (TDP-43) has been reported in semantic variant (sv-)PPA cases (2).