A syndromic neurodevelopmental disorder characterized by delayed psychomotor development, intellectual disability, truncal hypotonia, spasticity, and peripheral neuropathy. The disease is Monarch Disease Ontology term MONDO_0014958 (Harel-Yoon syndrome). Also known as: HAYOS, Harel-Yoon syndrome; HAYOS, optic atrophy-peripheral neuropathy-developmental delay syndrome.