Human Tay-Sachs patients have mutations in the HexA gene encoding for lysosomal β-hexosaminidase A resulting in accumulation of GM2 ganglioside (29), while sialidosis patients have mutations in the neuraminidase 1 (NEU1) gene, leading to lysosomal storage of sialylated glycoproteins (30, 31). The gene discussed is NEU1; the disease is sialidosis.