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J Clin Neurol. 2017 Oct;13(4):359-365. doi: 10.3988/jcn.2017.13.4.359. Epub 2017 Sep 4.

Ultrastructural Changes in Skeletal Muscle of Infants with Mitochondrial Respiratory Chain Complex I Defects.

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Department of Biomedical Laboratory Science, College of Health Sciences, Eulji University, Seongnam, Korea.
School of Life Sciences and Biotechnology, Korea University, Seoul, Korea.
Department of Pathology, Yonsei University College of Medicine, Seoul, Korea.
Epilepsy Research Institute, Yonsei University College of Medicine, Seoul, Korea.
Department of Pediatrics, Yonsei University College of Medicine, Seoul, Korea.
Contributed equally



The pathogenesis of mitochondrial disease (MD) involves the disruption of cellular energy metabolism, which results from defects in the mitochondrial respiratory chain complex (MRC). We investigated whether infants with MRC I defects showed ultrastructural changes in skeletal muscle.


Twelve infants were enrolled in this study. They were initially evaluated for unexplained neurodegenerative symptoms, myopathies, or other progressive multiorgan involvement, and underwent muscle biopsies when MD was suspected. Muscle tissue samples were subjected to biochemical enzyme assays and observation by transmission electron microscopy. We compared and analyzed the ultrastructure of skeletal muscle tissues obtained from patients with and without MRC I defects.


Biochemical enzyme assays confirmed the presence of MRC I defects in 7 of the 12 patients. Larger mitochondria, lipid droplets, and fused structures between the outer mitochondrial membrane and lipid droplets were observed in the skeletal muscles of patients with MRC I defects.


Mitochondrial functional defects in MRC I disrupt certain activities related to adenosine triphosphate synthesis that produce changes in the skeletal muscle. The ultrastructural changes observed in the infants in this study might serve as unique markers for the detection of MD.


infant; mitochondria; muscle pathology; respiratory chain complex; transmission electron microscopy; ultrastructure

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