PLP1, the gene encoding PLP and DM20, is located on the X chromosome; multiple copies of PLP1, deletion of PLP1,or point mutations in PLP1 can lead to the X-linked dysmyelinating disorders, Pelizaeus-Merzbacher disease (PMD), and spastic paraplegia type 2 (SPG2) [3, 4]. The gene discussed is PLP1; the disease is Pelizeaus-Merzbacher spectrum disorder.