The phenotype of mice with Pex2, Pex5 and Pex13 deficiencies resembles the features of human Zellweger syndrome, showing severe hypotonia and cerebral and cerebellar malformation.30, 31, 32 Pex11b deficiency in mice results in several pathological features shared by Zellweger syndrome, including neuronal migration defects, enhanced neuronal apoptosis, developmental delay, hypotonia and neonatal lethality.33 In the present study, another Pex11 family member, Pex11a, which acts as a membrane elongation factor during peroxisome proliferation,17, 25 may be involved in brain pathology. This evidence concerns the gene PEX13 and Zellweger syndrome.