Nuclear-encoded disorders (38%, n=22) were subcategorized into defects in protein transport (SLC25A4), small molecular metabolism (ECHS1, Pyruvate Carboxylase Deficiency, Dihydrolipoamide Dehydrogenase Deficiency, and Inorganic Pyrophosphatase Deficiency), protein translation (GTPBP3, TRIT1, MTO1, NARS2), mitochondrial structure/integrity (OPA1, TAZ), mitochondrial maintenance/integrity (POLG, TOP3A), and nuclear complex function (NDUFAF1, NDUFV1, SURF1, TMEM70) (Table 1). The gene discussed is OPA1; the disease is hyperinsulinemic hypoglycemia, familial, 4.