Overexpression of human APP in olfactory sensory neurons (OSNs) induces abnormal axonal projections of OSNs residing in the olfactory epithelium (OE) to the olfactory bulb (OB)20 and cell-autonomous cell death.21 Many previous studies have focused mainly on the OB and the central olfactory system rather than on OE and the peripheral olfactory organs, to explain the olfactory dysfunction observed in AD. Here, APP is linked to Alzheimer disease.