Zellweger spectrum disorders (ZSDs), including archetypal Zellweger syndrome, neonatal adrenoleukodystrophy (NALD) and infantile Refsum disease (IRD), are PBDs caused by mutations in peroxin genes (PEX1, PEX2, PEX3, PEX5, PEX6, PEX10, PEX11β, PEX12, PEX13, PEX14, PEX16, PEX19 or PEX26). This evidence concerns the gene PEX5 and Zellweger syndrome.