Novel NARS2 variants in a patient with early-onset status epilepticus: case study and literature review

Background: NARS2 as a member of aminoacyl-tRNA synthetases was necessary to covalently join a specific tRNA to its cognate amino acid. Biallelic variants in NARS2 were reported with disorders such as Leigh syndrome, deafness, epilepsy, and severe myopathy. Methods: : Detailed clinical phenotypes were collected and the NARS2 variants were discovered by whole exome sequencing and verified by Sanger sequencing. Additionally, 3D protein structure visualization was performed by UCSF Chimera. Results: : The proband in our study had early-onset status epilepticus with abnormal EEG and MRI results. She also performed global developmental delay (GDD) and myocardial dysfunction. Next-generation sequencing (NGS) and Sanger sequencing revealed compound heterozygous missense variants [NM_024678.6:exon14:c.1352G>A(p.Arg451His); c.707T>C(p.Phe236Ser)] of the NARS2 gene. The proband develops refractory epilepsy with GDD and hyperlactatemia. Unfortunately, she finally died for status seizures two months later. Conclusion: We discovered two novel missense variants of NARS2 in a patient with early-onset status epilepticus and myocardial dysfunction. The NGS enables the patient to be clearly diagnosed as combined oxidative phosphorylation deficiency 24 (COXPD24, OMIM:616239), and our findings expands the spectrum of gene variants in COXPD24.