PLP, encoded by the PLP1 gene and expressed in oligodendrocytes and other glial cells [18], not only contributes structurally but mutations therein lead to diverse myelin disorders, notably multiple sclerosis (MS), spastic paraplegia type 2 [19], and Pelizaeus–Merzbacher disease (PMD) [20]. The gene discussed is PLP1; the disease is myeloid sarcoma.