COQ4 and coenzyme Q10 deficiency: According to the literature, the first patient with a COQ4 variant and primary CoQ10 deficiency was reported by Salviati et al.(2012), in 2012; they reported a boy with a severe encephalomyopathic disorder carrying a de novo heterozygous 3.9 Mb deletion affecting at least 80 genes, including COQ4. Thus, haploinsufficiency of COQ4 was considered to be the cause of CoQ10 deficiency in this patient (Salviati, et al., 2012).