RRM2B and mitochondrial oxidative phosphorylation disorder: Of these, 29 patients harbored 41 disease-causing mutations in 20 genes known to cause OXPHOS disease: ACAD9, BOLA3, COQ4, COX10, EARS2, ECHS1, GFM1, GTPBP3, KARS, MPV17, NDUFA10, NDUFAF6, NDUFB11, NDUFS4, RARS2, RRM2B, SCO2, SUCLA2, TAZ, and TUFM. All such mutations were confirmed through Sanger sequencing and haplotype phasing.