So far this list contains single enzyme deficiencies like Refsum disease (PHYH deficiency), racemase, MFP2 and SCPx deficiency, as well as biogenesis disorders such as Zellweger syndrome, neonatal adrenoleukodystrophy, infantile Refsum disease and rhizomelic chondrodysplasia punctata. The gene discussed is HSD17B4; the disease is Zellweger spectrum disorders.