a Pedigree of the studied Moroccan family with X-linked epileptic seizures, presenting the co-segregation of the c.251C > A mutation. The patient above the arrow indicates the proband. b Chromatograms by Sanger sequencing of family members who are hemizygous, heterozygous and wild-type for the PLP1 variant. c Amino acid conservation map across species demonstrating a highly conserved residues position 84 (based on Multiz Alignments Track of UCSC Genome Browser and The human genome reference hg19/GRCch37)