ACOX1 and Peroxisome biogenesis disorder-Zellweger syndrome spectrum: If this is negative, it is important to consider other peroxisomal disorders, such as 1) peroxisomal biogenesis disorders with late onset of symptoms [74,75] (Ebberink et al, in press), and 2) peroxisomal acyl-CoA oxidase 1 (ACOX1) or D-bifunctional enzyme (DBP) deficiency with late onset of symptoms.