Introduction: Mutations in the RMND1 gene that cause defects in the mitochondrial respiratory chain result in a highly variable phenotypic presentation. The protein required for meiotic nuclear division 1 homolog (RMND1) is localized to the inner mitochondrial membrane and is encoded by the nuclear genome. Case Presentation: We report a new patient from a consanguineous family who was severely affected by a previously described combined oxidative phosphorylation deficiency 11 and was treated rapidly due to early diagnosis. Methods: We also included patients with RMND1 mutation in the literature. We analyzed the epidemiological, clinical, laboratory, and genetic data of a total of 49 patients (98 alleles) in the literature, including our patient. We summarized all previously published patients and focused on the importance of early diagnosis. Results: The most common variant in patients with RMND1 mutation was c.713A>G (p.Asn238Ser). Mortality was significantly lower in patients with homozygous and compound heterozygous c.713A>G (p.Asn238Ser) mutations ( Conclusion: In this study, the effect of cardiac involvement on mortality in RMND1 mutation was shown for the first time. We reported that mortality was lower in the c.713A>G (p.Asn238Ser) mutation. Furthermore, mortality was more common in the c.1349G>C (p.*450Serext*32) mutation. These findings have not been previously reported in the literature. They are reported for the first time in this study.