Huizing et al. Page 25 (NANS) deficiency (MIM#605202; ~9 cases [40]); and (3) deficiency of SLC35A1, CDGIIf A uthor Man (MIM#603585; ~3 cases [129]) are characterized by decreased sialylation of glycans; (4) Sialidosis (MIM#256550; >100 cases [132]) is characterized by lysosomal accumulation of sialylated glycans. Three disorders are associated with increased urinary excretion of free Neu5Ac: (5) Sialuria (MIM#269921; ~ 11 cases [33]); (6) FSASD (MIM#269920, #604369; uscr ~200 cases [1]); and (7) NPL deficiency (2 cases [38]). ipt A uthor Man uscr ipt A uthor Man uscr ipt A uthor Man uscr ipt Neurosci Lett. Author manuscript; available in PMC 2021 June 11.