Two siblings with combined oxidative phosphorylation defect 11 with a novel mutation in the RMND1 gene

Objectives RMND1 protein belongs to a large mitochondrial inner membrane complex that supports translation of the mtDNA-encoded polypeptides.Mutations in the RMND1 gene have recently been linked to infantile onset mitochondrial disease characterised by multiple mitochondrial respiratory chain defects named as combined oxidative phosphorylation defect 11(COXPD11).The clinical phenotypes are expanding a fatal,infantile encephalomyopathy with lactic acidosis to a less severe phenotype characterised by developmental delay,congenital sensorineural deafness,hypotonia and renal disease. Methods Herein,we present two sibling wit of the RMND1-associated COXPD11 with a novel homozygous mutation. Results A 11-year-old female who is the first child of healthy and consanguineous parents.Her medical history remarkable with a difficult birth,congenital hearing loss,hyperactivity and developmental delay.Her cousins and brother also had developmental delay and hearing loss.She was admitted due to the seizures for one year.In her examination, she had no communication with the environment. Metabolic screening was normal except for increased plasma lactate level.Active multifocal epileptic disorder in EEG and symmetrical signal increase in bilateral lentiform nuclei on brain MRI were detected.MR spectroscopy normal.Karyotype and microarray analysis were normal.Whole exome sequencing identified a novel homozygous c.791T>A (p.V264E) mutation in the RMND1 gene(NM_017909.4). Family screening also revealed same homozygous mutation in her 8 year-old brother with similar clinical findings and heterozygous mutation in her parent and the other sibling. Conclusion Herein, we described two siblings with a novel homozygous mutation of RMND1 gene with severe neurologic phenotype without renal involvement.