COQ2 and coenzyme Q10 deficiency: It is interesting to note that some patients with inherited pathogenic variants in genes implicated in primary CoQ10 deficiency manifest with optic atrophy as a feature of complex neurological phenotypes, including mutation of COQ1/PDSS1 (Mollet et al, 2007; Nardecchia et al, 2021), COQ2 (Stallworth et al, 2023) and COQ6 (Justine Perrin et al, 2020).