MAPT and Alzheimer disease: According to the US National Institute on Aging-Alzheimer's Association workgroup, there are three different stages of AD: preclinical AD (presymptomatic with early AD-related brain changes observed by neuroimaging or other biomarker studies such as amyloid and tau studies in cerebrospinal fluid (CSF)), mild cognitive impairment (MCI) caused by AD (mild cognitive decline but still able to perform daily activities), and dementia caused by AD (major cognitive decline that interferes with daily activities) [6].