In this context, the complex genotype of patient 1 could explain his severe CIE phenotype; indeed, besides the 12R-LOX deficiency caused by the two pathogenic variants p.Leu451Alafs* and p.Tyr687del, the ABCA12 missense variant p.Glu2138Ala can be reasonably considered a hypomorphic allele that negatively modified the patient’s phenotype [19,33]. The gene discussed is LOX; the disease is hyperinsulinemic hypoglycemia, familial, 4.