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Objective: To analysis the clinical, molecular features, as well as the bond of them in mitochondrial disorders with mtDNA variation. Methods: The clinical and genetic data of patients with mitochondrial disorders harbored by mtDNA variations in Beijing Children’s Hospital, Capital Medical University from 2013 to 2018. Results: There were total 154 diagnosed cases collected in our study, involving 28 mtDNA point mutations, 4 large-single scale mtDNA deletions, referring to 11 genes (MT-ND1, ND3, ND4, ND5, ND6, TI, TE, TL1, TK, RNR1, ATP6), 4 gene families (tRNA, rRNA, complexⅠ, complexⅤ) . The top 4 genotypes are A3243G (n=75, 48.7%), T8993G or T8993C (n=11, 7.1%), A8344G (n=9, 5.8%), T9176C (n=9, 5.8%). The phenotypes of 154 cases are MELAS (n=73, 47.4%), Leigh syndrome (n=52, 33.8%), Leber hereditary optic neuropathy (LHON) and LHON plus (n=9, 5.8%), MERRF (n=6, 3.8%), mitochondrial myopathy (n=5, 3.2%), Kearns-Sayre syndrome (n=4, 2.6%), deafness (n=1, 0.6%), mitochondrial diabetes and deafness (n=1, 0.6%). And MELAS/LS (n=2, G13513A) and MERRF/LS (n=1, A8344G) were found in this group. Moreover, among the 9 cases of T9176C mutation who were all diagnosed as Leigh syndrome, 4 (44.4%) were death cases for different causes. Conclusions: Mitochondrial DNA disorders with high heterogeneity were the important part of genetic features of mitochondrial disorders. The early molecular diagnosis was indispensable for the suspected mtDNA disorders. Moreover, the phenotype, genotype and the relation of them could give us lots of useful information for the early diagnosis, evaluation, treatment, complication management, prognosis, etc.

Mitochondrial DNA Variations; Mitochondrial Diseases; Molecular Features; Clinical characteristics;