Clinical Analysis of Mitochondrial Respiratory Chain Enzyme Deficiency in Children: Report of 7 Cases

Abstract

Objective To investigate the clinical features of the non-syndromic mitochondrial disease in children which were identified by mitochondrial respiratory chain enzyme complex activity assay. Methods From March 2010 to April 2011, seven children who were diagnosed as non-syndromic mitochondrial disease were included into this study. The enzyme activity of respiratory chain enzyme complexes (Ⅰ-Ⅳ) and ATP synthase (complex Ⅴ) in peripheral blood leukocytes of 7 children were determined. All the children whose routine screening of mitochondrial genes were negative. Children's clinical data were retrospectively analyzed. Results ①There were intelligence backwards after infection in 5 cases, combined seizures in 4 cases, paralysis in 6 cases; deafness, ataxia in 2 cases, combining anterior pituitary hypofunction/episodes of hypoglycemia in 1 case; myodynamia and hypomyotonia in 7 cases. The findings of brain MRI were abnormal in 6 cases, the findings of electroencephalogram (EEG) were abnormal in 5 cases and abnormal findings of electromyography (EMG) in 3 cases. Blood lactate increased slightly in 3 cases, the level of myocardial enzyme were abnormal in 2 cases. ②Conventional mitochondrial genes screening was negative. ③ 4 childen had isolated complex defects: complex Ⅱ deficiency (2 cases), complex deficiency of Ⅰ or Ⅳ (1 case, respectively); 3 cases were found to have combined deficiencies: 2 cases had combined deficiencies of complex Ⅰ and Ⅲ, 1 case had combined deficiencies of complex Ⅱ and V. Conclusions Mitochondrial respiratory chain enzyme deficiency in children may present non-specific neurological symptoms, the clinical features were extensive involvement of multi-system, and regular screening of mitochondrial gene was negative, the mitochondrial respiratory chain enzyme activity assay of peripheral leukocyte may help to identify the non-syndromic mitochondrial disease. Key words: mitochondrial respiratory chain enzyme deficiency; respiratory chain enzyme complex activity; child