PEX5 and Zellweger syndrome: In Zellweger syndrome, which is inherited in an autosomal recessive manner, one of 13 peroxin (PEX) genes is mutated (PEX1, PEX2, PEX3, PEX5, PEX6, PEX10, PEX11β, PEX12, PEX13, PEX14, PEX16, PEX19, PEX26), leading to issues with neuronal migration, myelination and brain development (Waterham and Ebberink, 2012; Klouwer et al., 2015; Wang et al., 2015).