We propose Sanger sequencing to identify compound heterozygous ACO2 variants, supported by the gene's eight ‘green status’ whole genome sequence panels in the UK PanelApp: Optic Neuropathy; Retinal Disorders; Inborn Errors of Metabolism; Undiagnosed Metabolic Disorders; Mitochondrial Disorders; Possible Mitochondrial Disorder—Nuclear Genes; Intellectual Disability and Severe Paediatric Disorders [6]. Here, ACO2 is linked to Intellectual disability.