Mutations affecting genes that encode classical myelin proteins including PLP, CNP, MAG, TUBB4, and ASPA cause severe neurological disorders including hypomyelinating leukodystrophies (HLD) and spastic paraplegias (SPG) (Kaul et al., 1993; Saugier-Veber et al., 1994; Simons et al., 2013; Lossos et al., 2015; Al-Abdi et al., 2020) (Table 1). The gene discussed is CNP; the disease is Spastic paraplegia.