Coenzyme Q10 Supplementation in a Child with Biallelic

Introduction: Pathogenic variants in COQ8A cause a rare form of primary coenzyme Q10 (CoQ10) deficiency that can lead to childhood-onset cerebellar ataxia and developmental delay. However, reports of pediatric cases remain limited, and evidence regarding therapeutic response to CoQ10 supplementation in children is still scarce. Case Presentation: We report a 7-year-old boy with compound heterozygous COQ8A variants who presented with progressive cerebellar ataxia and intellectual disability. Oral CoQ10 supplementation was initiated at a dose of 10 mg/kg/day after institutional ethics approval. During 1 year of treatment, the Scale for the Assessment and Rating of Ataxia (SARA) score improved from 17 to 9, and serum CoQ10 concentration increased from 622 to 9.100 ng/mL. Mild cognitive improvement was also observed, with the intelligence quotient increasing from 53 to 64. Brain MRI demonstrated radiological stabilization of cerebellar atrophy. No adverse effects related to CoQ10 supplementation were observed throughout the treatment period. Conclusion: This case demonstrates the clinical benefit and safety of CoQ10 supplementation in pediatric-onset COQ8A-related ataxia. Early genetic diagnosis and timely initiation of CoQ10 therapy may lead to meaningful neurological improvement and stabilization of disease progression in affected children.