Among nuclear DNA (nDNA)-related diseases, combined oxidative phosphorylation deficiency (COXPD1), encephalopathy due to defective mitochondrial and peroxisomal fission 1 (EMPF1), and primary coenzyme Q10 deficiency (COQ10D7) were the most frequently encountered, each constituting 14.3% of cases, and were linked to metabolic or mitochondrial dysfunctions. Here, GFM1 is linked to combined oxidative phosphorylation deficiency.