HSD17B4 and X-linked adrenoleukodystrophy: Peroxisomal disorders observed in rare genetic diseases are grouped as peroxysomopathies, which include peroxisomal biogenesis disorders (such as Zellweger syndrome) and single and/or multiple peroxisomal enzyme deficiencies (X-linked adrenoleukodystrophy (X-ALD), acyl CoA-oxidase-1 (ACOX-1) deficiency, and D bifunctional protein (MFP2) deficiency) [24].