MT-CYB and hyperinsulinemic hypoglycemia, familial, 4: While Patient 2 shows decreased steady-state levels of mitochondrial-encoded OXPHOS subunits NDUFB8 (of complex I), COXI/COXII (of complex IV) and CYTB/CORE2 (of complex III), indicating a combined OXPHOS deficiency, steady-state OXPHOS protein levels were relatively unchanged in Patient 1 when compared to controls (Fig. 3a).