Neuropil threads and neurofibrillary tangles of tau protein have been observed in the olfactory bulb and olfactory nerve in all cases of definite AD, as well as in many cases of probable AD, MCI, and even cognitively normal aging (Christen-Zaech et al., 2003; Attems and Jellinger, 2006). The gene discussed is MAPT; the disease is Alzheimer disease.