NEU1 and sialidosis: The importance of NEU1’s function for proper lysosomal catabolism and maintenance of cell and tissue homeostasis is exemplified by the severe systemic and neurological consequences of NEU1 deficiency in patients with the lysosomal storage diseases (LSDs) sialidosis, primary deficiency of NEU1, and galactosialidosis secondary deficiency of NEU1 due to a primary defect in PPCA [3,4].