Primary coenzyme Q10 deficiencies are a group of clinically heterogeneous mitochondrial diseases caused by problems in the biosynthesis steps of CoQ10. They are inherited in an autosomal recessive manner. To date, approximately 280 patients from 180 different families have been reported. The worldwide incidence is estimated to be 1/50,000. The lack of a clear genotype-phenotype correlation, the multisystemic involvement of the disease, and the variability of clinical findings and age of onset can lead to delays in the diagnosis and prognostic evaluation process.
Mutations in genes encoding proteins involved in the endogenous synthesis of coenzyme Q10 cause primary CoQ10 deficiencies. Of the genes involved in CoQ10 metabolism, PDSS1, PDSS2, COQ2, COQ4, COQ5, COQ6, COQ7, COQ8A, COQ8B, and COQ9 genes have been reported to cause primary CoQ10 deficiency.
COQ9 gene defects are associated with a multisystem disorder characterised by a wide range of clinical features. Neurological abnormalities presenting as cognitive impairment, developmental delay and seizures are commonly observed in affected individuals. In addition, muscle weakness and cardiac manifestations, including hypertrophic cardiomyopathy, may be prominent aspects.
The prevalence of COQ9 gene defects is not well defined due to the rarity of the condition. COQ9 deficiency is autosomal recessively inherited. Genetic mutations affecting COQ9 gene disrupt the normal function of coenzyme Q10 (CoQ10) biosynthesis. CoQ10 plays a critical role in cellular energy production and its deficiency due to COQ9 gene mutations leads to the multisystem manifestations seen in affected individuals.
Healthcare professionals need to consider COQ9 gene defects in the differential diagnosis of individuals presenting with neurological, muscular or cardiac symptoms, as early detection and intervention can significantly impact patient outcomes. Genetic testing is an important diagnostic tool to confirm the disease and guide appropriate management strategies for affected individuals. Ongoing research aims to further elucidate the clinical spectrum, improve diagnostic approaches and explore potential therapeutic interventions for this complex multisystem disorder.
COQ9