Mutations in genes that affect sialylation are associated with neurological symptoms in human, including intellectual disability, epilepsy, and ataxia due to defects in sialic acid synthase (N-acetylneuraminic acid synthase [NANS]), sialyltransferases (ST3GAL3 and ST3GAL5), the CMP-Sia transporter (SLC35A1), and CMP-Sia synthase (CMAS) (Hu et al., 2011; Mohamed et al., 2013; Boccuto et al., 2014; van Karnebeek et al., 2016). The gene discussed is NANS; the disease is cerebellar ataxia.