MAPT and Alzheimer disease: Clusters of AD diagnosed patients were identified and characterized by different degree of executive functions impairment, high levels of CSF tau and phosphorylated tau with low levels of Aβ 1-42, presence of apathy, limited or absent response to pharmacological treatment with cholinesterase inhibitors (Van der Vlies et al., 2009; Mitchell et al., 2011; Iqbal et al., 2013; Koch et al., 2013; Horvath et al., 2014).