Genotype-phenotype Correlation in Pelizaeus Merzbacher Disease and Pelizaeus Merzbacher-like Disease

Pelizaeus-Merzbacher disease (PMD) is the prototype of hypomyelinating diseases of childhood which was firstly described as an X-linked disorder caused by mutations or rearrangements in the proteolipid protein 1 (PLP1) gene. Causative mutations of the PLP1 gene are-in declining order of frequency-duplications, point mutations, insertions, and deletions (1). Clinical features include nystagmus (typically occurs in the first months of life and resolves within 2-5 years of age), dysarthria, ataxia, hypotonia and developmental delay evolving into spastic quadriplegia in the first years of life (2). The clinical severity and rate of progression vary widely, probably depending on the variability of the causative mutation (1). Although, it was firstly described as a X-linked disorder, patients with PMD phenotype but without mutations of PLP1 gene were shown to have an autosomal recessive (OR) trait. One of the causative mutations in these patients -called