However, rod–cone dystrophy is an increasingly recognized phenotype and has been additionally reported in patients carrying pathogenic variants in MT-ATP6 (MIM *516060),28MT-TS2 (MIM *590085),29 and recently in COQ2 deficiency (MIM *609825),30 representing diverse functional pathways within the mitochondrion. Here, COQ2 is linked to hyperinsulinemic hypoglycemia, familial, 4.