PLP1 and Pelizeaus-Merzbacher spectrum disorder: Many of the leukodystrophies arise during development such as Pelizaeus-Merzbacher disease (PMD), which is a rare congenital disorder characterized by hypomyelination and is the result of duplication or missense mutation of the PLP1 gene, eventually leading to abnormal or reduced myelin formation and oligodendroglial death [50].