HHEX and Down syndrome: Plasma membrane and cytosol glycohydrolases, namely, Hexosaminidase (HEX), β-D-Glucuronidase (GCR), α-D-Glucosidase (α-GLU), and O-β-N-Acetyl-glucosaminidase (O-GlcNAcase,), were also found in human erythrocytes where [9, 10] they have a role in signalling early membrane alterations [6], in pathologies related to strong oxidative stress, such as type 2 diabetes mellitus [11] or Down's syndrome [12, 13].