Two LS fibroblast cell lines harbored pathogenic point mutation in the mtDNA at T8993G in the MTATP6 gene causing complex V deficiency, while the third LS fibroblast cell lines harbored pathogenic point mutation in the mtDNA at T10158C in the MTND3 gene and the fourth LS fibroblast cell lines harbored pathogenic point mutation in the mtDNA at T12706C in the MTND5 gene causing complex I deficiency. The gene discussed is MT-ND3; the disease is hyperinsulinemic hypoglycemia, familial, 4.