A single TBC1D24 variation (p.Ser178Leu) exchanging a highly conserved polar uncharged residue for a hydrophobic residue has been described previously in a European and a Chinese family by independent groups that cause AD HL with a similar age of onset and clinical course as the families under study (Azaiez et al., 2014; Zhang et al., 2014). Here, TBC1D24 is linked to Alzheimer disease.