Mutations in the COQ2 and COQ4 genes can lead to CoQ deficiency disorders such as multiple system atrophy and primary coenzyme Q10 deficiency (42, 43), which often result in mitochondrial dysfunction and a wide range of symptoms, including muscle weakness, neurologic abnormalities, and cardiomyopathy (44). This evidence concerns the gene COQ4 and coenzyme Q10 deficiency.