Carnitine- acylcarnitine translocase deficiency (CACTD, MIM: #212138) is an autosomal recessive fatty acid oxidation disorder caused by biallelic pathogenic variants in the gene SLC25A20 (OMIM: *613698) encoding the enzyme carnitine- acylcarnitine translocase (CACT). Here, SLC25A20 is linked to hyperinsulinemic hypoglycemia, familial, 4.