[P3-135] Mitochondrial disorders of neurological system in children from East China: clinical presentation, lab findings, muscle pathology, and molecular analysis
Mitochondrial disorders involving neuromuscular system in chidren are a clinically and molecularly heterogeneous group of diseases. We presented clinical symptoms, lab findings, muscle pathology, and molecular results for 32 mitochondrial disorder cases from East China. Among them were 15 boys and 17 girls,with onset age lying in the range of 1 day after birth to 15 years’ old(4.3 years’ old in average). 17 cases complained with muscle weakness or exercise intoleranee; 11 cases with motor development retardation or regression;other symptoms in turn was epilepsy, vomitting, ptosis, respiratory failure. 18/28 cases showed elevated CK levels; 19/23 cases showed elevated serum lactac acids levels; 14/22 cases showed abnormal cerebral MRI image. Muscle biopsy performed in eighteen cases showed pathological feature of mitochondrial myopathy. Molecular test revealed 21 pathogenic variants from mitochondrial DNA(mtDNA), that included m.3243A>G（mutation load from 12.3% to 95%）for 12 cases, m.3303 C > T for 2 cases，m.3302A>G，m.10191 T >C，m.14459G>A，m.14674 T> C，m.8344A>G，m.8993T>C and m.9176T>C for 1 case respectively; compound heterozygous variants in the TK2 gene for 2 patients; and 2 suspected mtDNA pathogenic variants. As for the m.3243A>G cases, the clinical presentation varied much from recurrent hypoglycemia and difficult breathing just one day after birth to single symptom of exercise intolerance at teenage. Our study expanded the phenotype and genotype of neurological mitochondrial disorders in childhood, and muscle biopsy and molecular test play a critical role for the diagnosis of mitochondrial diseases in chidren.