B4GALNT1 and aceruloplasminemia: Mutations in beta-1,4-N-acetyl-galactosaminyl transferase 1 (B4GALNT1; GM2 synthase) result in early-onset HSP, intellectual disability, cerebellar ataxia, peripheral neuropathy and cortical atrophy (Boukhris et al., 2013; Harlalka et al., 2013).