OBJECTIVETo delineate the clinical, biochemical and genetic mutational characteristics of a child with mitochondrial complex III deficiency.

METHODSClinical information and results of auxiliary examination of the patient were analyzed. Next-generation sequencing of the mitochondrial genome and related nuclear genes was carried out. Suspected mutation was confirmed in both parents with Sanger sequencing. Heterozygous deletion was mapped with chromosomal microarray analysis and confirmed with real-time PCR.

RESULTSThe patient presented with vomiting, polypnea, fever, metabolic acidosis, hyperlactatemia, hypoglycemia, dysfunction of coagulation and immune system, in addition with increased lactate dehydrogenase and creatine kinase isoenzyme. Elevation of blood alanine and acylcarnitines as well as urinary ketotic dicarboxylic acid were also noted. The patient also presented development delay, mental retardation and hypotonia. Sequence analysis revealed two mutations in the nuclear gene UQCRB, which included a previously reported frameshift mutation c.306_309delAAAA(p.Arg105Lysfs*22) and a novel large deletion encompassing the entire UQCRB gene.

CONCLUSIONThe clinical, biochemical and gene mutation characteristics of a child with mitochondrial complex III deficiency caused by mutations of the UQCRB gene have been delineated.