NEU1 and sialidosis: Sialidosis, also known as Mucolipidosis Type I, is caused by autosomal recessive mutations in the NEU1 gene, encoding the lysosomal enzyme neuraminidase-1 (NEU1; also known as sialidase), a glycosidase that removes terminal sialic acid residues from sialo-rich oligosaccharides, glycoproteins and glycolipids (168).