Moreover, secondary CoQ10 deficiency has been reported in patients with mitochondrial DNA depletion due to mutations in DGUOK (encoding mitochondrial deoxyguanosine kinase, which is involved in the purine nucleotide salvage pathway), SUCLA2 (encoding the β subunit of succinyl-CoA synthase, which is involved in the Krebs cycle), MPV17 (involved in mitochondrial deoxynucleoside triphosphates pool homeostasis) or from unknown etiology [81,82]. Here, DGUOK is linked to hyperinsulinemic hypoglycemia, familial, 4.