For newborn screening, positives with VUS or known benign variants in ABCD1 and abnormal biochemistry, other peroxisomal biomarkers (i.e., plasmalogens, phytanic acid, pristanic acid, and bile acid intermediates) should be analyzed to exclude related diseases such as Zellweger spectrum disorder, ACOX1 (or HSD1B4) deficiency, CADDS, ACBD5 deficiency, and Aicardi-Goutières syndrome.24 The gene discussed is ACOX1; the disease is hyperinsulinemic hypoglycemia, familial, 4.