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 hereditary optic atrophy.