Background and objective: So far, over 100 large mitochondrial DNA (mtDNA) deletions have been identified. Those large deletions can lead to a broad spectrum of clinical features including mild mitochondrial myopathies (MM), progressive external ophthalmoplegia (PEO), Kearns-Sayre syndrome (KSS) and Pearson syndrome (PS). Pediatric patients have been paid much attention because mitochondrial disorders in children are diverse and many clinical features are difficult to distinguish. The study aims to investigate the large mtDNA deletions in the Vietnamese pediatric patients with clinical features of mitochondrial disorders.
Methods: Total DNAs were extracted from blood samples of 62 pediatric patients with clinical features of mitochondrial disorders and 19 pediatric patients without clinical features of mitochondrial disorders collected at Vietnam National Hospital of Pediatrics. The large mtDNA deletions were determined by using nested PCR and PCR-sequencing of the deletion junctions.
Results: Using nested PCR, the large mtDNA deletions in pediatric patients with clinical features of mitochondrial disorders were identified with 72.58% (45/62 cases) carrying 4,977 bp deletion and 20.97% (13/62 cases) carrying multiple large mtDNA deletions. Using PCR-sequencing of deletion junctions, some novel large mtDNA deletions were also detected, including: 4,443, 4,701, 4,732, 4,814, 4,860, 4,969, 4,994, 5,122, 5,135 and 5,144 bp deletions. The large mtDNA deletions in pediatric patients without clinical features of mitochondrial disorders were also detected with 89.47% (17/19 cases) carrying 4,977 bp deletion and only 5.26% (1/19 cases) carrying the multiple large mtDNA deletions. Therefore, further studies have been being conducted to determine the multiple large mtDNA deletions in Vietnamese pediatric patients.
Conclusions: The 4,977 bp deletion is a common mtDNA deletion in Vietnamese pediatric patients. In 20.97% of pediatric patients with clinical features of mitochondrial disorders harboring the multiple large mtDNA deletions, some novel large mtDNA deletions have been found.
