Early endosomal swelling has been reported repeatedly as a very early event in AD neuronal pathology (Cataldo et al., 2000; Decourt et al., 2013; Nixon et al., 2001) using several early endosome markers including EEA1, Rab4 (Rab4a and Rab4b) and Rab5. Here, RAB4A is linked to Alzheimer disease.