MAPT and Alzheimer disease: As the key molecules in the pathogenesis of AD (Bloom, 2014), Aβ and/or tau protein have been detected in the form of protein pathology in patients’ olfactory system (Son et al., 2021), including olfactory epithelium (Arnold et al., 2010), olfactory bulb (Attems et al., 2014), piriform cortex (Saiz-Sanchez et al., 2015), the glomerular layer (Bathini et al., 2019b), anterior olfactory nucleus (Bathini et al., 2019b; Ubeda-Banon et al., 2020), and olfactory tubercle (Bathini et al., 2019b).