[Primary coenzyme Q10 deficiency-7: a case report and literature review]

Objective: To explore the clinical characteristics and gene variation of primary coenzyme Q10 deficiency-7 (COQ10D7) in children. Methods: Clinical data and genetic tests results of a COQ10D7 child caused by coenzyme Q4 (COQ4) gene variation at the First Affiliated Hospital of Xiamen University in March 2020 were collected and analyzed. A literature search with "primary coenzyme Q10 deficiency" or "COQ4 gene" as the keyword was conducted at Wanfang database, China national knowledge infrastructure(CNKI), PubMed, online Mendelian inheritance in man(OMIM), ClinVar database (up to April 2020), the clinical characteristics and gene variation of children with primary COQ10D7 were summarized. Results: A 5-month-old boy was diagnosed as "epilepsy" because of intermittent epileptic seizures in three months. He had feeding difficulties, growth retardation, hypotonia of limbs and increased lactic acid. His whole exon gene testing suggested a homozygous variation of COQ4 gene (c.370G>A). One article in Chinese and 9 articles in English were found, which made up the complete case data of 33 patients (including our case). There were 12 missense variations, 2 frameshift variations, 1 splicing variation, 1 nonsense variation and 1 deletion variation, among these variations c. 370G>A was found only in children in southern China.The age of onset was mostly in the neonatal period (22 cases). Among all patients, 20 cases had presented neonatal respiratory distress or respiratory insufficiency, 21 cases had seizures, 20 cases had hypertrophic cardiomyopathy, and 26 cases had elevated serum lactic acid or lactic acidosis. Brain dysplasia, brain atrophy, basal ganglia and other lesions were observed on brain magnetic resonance imaging in 28 cases. Most of them had a poor prognosis with a mortality rate of 20/33. The age of death ranged from 4 hours to 42 months old. Conclusions: The main clinical phenotypes of primary COQ10D7 are neonatal respiratory distress or respiratory insufficiency, epilepsy, myocardial hypertrophy and lactic acid elevation. Primary COQ10D7 is caused by homozygous or compound heterozygous variation in the COQ4 gene, and c.370G>A may be the hotspot variation in children in southern China.