The cytochrome c oxidase assembly factor 5 (COA5) gene (RefSeq: NM_001008215.3), previously denoted as C2orf64, was first reported in humans when a homozygous missense variant (c.157G>C, p.Ala53Pro) in this gene was shown to cause mitochondrial disease. Here, COA5 is linked to inborn mitochondrial metabolism disorder.