Most species have a single ATAD3 gene but hominids have a cluster of three genes arranged in tandem close to the telomere of chromosome 1p: ATAD3C, ATAD3B and ATAD3A. A recurrent de novo dominant missense mutation in ATAD3A was recently shown to cause a phenotype comprising global developmental delay, hypotonia, optic atrophy, axonal neuropathy, and hypertrophic cardiomyopathy in five unrelated subjects (Harel et al., 2016). This evidence concerns the gene ATAD3A and optic atrophy.