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). The gene discussed is PEX2; the disease is Zellweger syndrome.