PLP1 and pathologic nystagmus: Pelizaeus Merzbacher Disease (PMD) is a rare X-linked central nervous system (CNS) disease involving the proteolipid protein 1 (PLP1) gene on Xq22.1 PLP1 gene codes for myelin protein which leads to hypomyelination.1 PLP1 gene is one of leukodystrophies characterized by degeneration of white matter in CNS.1 Patients exhibit signs that progressively worsen for instance nystagmus, hypotonia, ataxia, convulsions, muscle contractions, language delay.2,3 PMD affects males more than females.