Our sibling pair with CACT deficiency was compound heterozygous for the known p.Asn300Glnfs*24 variant in SLC25A20. Interestingly, a patient with CACT deficiency who was homozygous for the same variant had a neonatal onset hypoglycemia but had a milder phenotype and was 9 years old at the time the publication [45]. This evidence concerns the gene SLC25A20 and hyperinsulinemic hypoglycemia, familial, 4.