Abstract
Background: Peroxisomes are cells' organelles that responsible for the metabolism of branched-chain and very-long-chain fatty acids (VLCFA), polyamines, and amino acids. Peroxisomal biogenesis factor 6 (PEX6) is one of the factors required for the import of the proteins into peroxisomes. Mutation in any one of PEX genes will result in Zellweger syndrome (ZS), one of the peroxisome biogenesis disorder.
Case Presentation: A 11-year-old girl referred was with central hypotonia and global developmental delay and feeding problems. She has an open and flat fontanel. Liver function tests and thyroid-stimulating hormone were elevated. Plasma VLCFA C26, VLCFA C24/C22, and VLCFA C26/C22 were elevated. Cerebrospinal fluid flow artifact and posterior displacement of the basilar artery findings raised the possibility of increased intracranial pressure. X-ray showed mild irregularity in the end plates of the lumbar vertebrae, bilateral coxa
valga, irregularity in the articular surfaces of the ossified epiphysis of the upper and lower limbs, and generalized osteopenia. The audiological assessment profound hearing loss in both ears. Inborn error of metabolism, next-generation sequencing gene panel analysis, and whole exome sequencing showed that no pathogenic or likely pathogenic variants explaining the phenotypes. The single nucleotide polymorphisms testing showed a deletion in PEX6 gene (homozygous variant of uncertain significance).
Conclusion: We report a case of ZS associated with a new PEX6 mutation that has not been previously reported in the literature.

Key words: Peroxisome biogenesis disorder, PEX6 gene, Saudi Arabia, VLCFA, Zellweger syndrome