VLCFA accumulation as the dominant biochemical abnormality is also observed in the peroxisomal disorders X‐ALD and ACOX1‐deficiency.79 ACBD5‐deficient patients develop clinical symptoms such as progressive leukodystrophy, ataxia, retinal dystrophy, cleft palate, and facial dysmorphism, which resemble those of patients suffering from ACOX1 deficiency, but are different from X‐ALD, where, for example, retinopathy does not manifest. This evidence concerns the gene ACOX1 and hyperinsulinemic hypoglycemia, familial, 4.