In the LS subgroup WES expanded the set of patients from our centre diagnosed with complex I deficiency by three known genes: NDUFS6 [63, 64], NDUFV1 [65, 66], NDUFS7 [67], a new candidate NDUFB8 [68] and five MTNDs mentioned above. The gene discussed is NDUFS7; the disease is hyperinsulinemic hypoglycemia, familial, 4.