PLP1 and Pelizeaus-Merzbacher spectrum disorder: Although our three variants are novel, several other mutations in exon 3B have been described [6,7,8,9,10,11,12,13,14,15] and have been associated with either classic PMD [9,10,13,14], “mild” PMD [12,15], or SPG2 phenotype [6,7,8,11].