ABSTRACT
A term infant born small for gestational age presented with tachypnea as the first symptom one week after birth and had recurrent lactic acidosis. Whole-exome sequencing revealed compound heterozygous variants of c.1640C>T(p.A547V) and c.1274delG(p.G425Efs*23) in MTO1 gene, based on which the patient was diagnosed as combined oxidative phosphorylation deficiency type 10. The patient developed Klebsiella pneumoniae sepsis and died at 41 days of age. Combined oxidative phosphorylation deficiency type 10 is a type of mitochondrial disease inherited in an autosomal recessive manner. Patients with the onset of symptoms in the neonatal period are likely to have a poor prognosis and there is no effective treatment at present. The heterozygous variants of c.1640C>T and c.1274delG detected in this case are de novo variants, which expand the spectrum of variants in MTO1 gene.