A study of 133 Chinese children with mitochondrial respiratory chain complex I deficiency.

To investigate the clinical, enzymological and mitochondrial gene profiles of complex I deficiency in Chinese, clinical and laboratory data of the patients (79 boys, 54 girls) were retrospectively assessed. Activities of mitochondrial respiratory chain complexes in peripheral leucocytes were spectrophotometrically measured. The entire mitochondrial DNA (mtDNA) sequence was analyzed in 62 patients. Restriction fragment length polymorphism and gene sequencing analyses were performed in 15 families. Ninety-one patients had isolated complex I deficiency; 42 had combined deficiencies of complex I and other complexes. The main clinical presentations were neuromuscular disorders (107 patients) and non-neurological dysfunction (hepatopathy, renal damage and cardiomyopathy; 26 patients). In 32 of 62 patients who underwent mtDNA sequencing, 24 mutations were identified in 15 mitochondrial genes. The 12338T>C, 4833A>G and 14502T>C mutations were found in 12.9%, 11.3% and 4.8% patients, respectively. Seven patients had multiple mutations. Three novel mutations were identified. Chinese patients with complex I deficiency presented heterogeneous phenotypes and genotypes. Twenty-four mutations were identified in 15 mitochondrial genes in 51.6% patients. mtDNA mutations were more common in isolated complex I deficiency than in combined complex deficiencies. The 12338T>C, 4833A>G and 14502T>C mutations were common.