The newly described 2q23.1 microdeletion syndrome includes severe intellectual deficit with pronounced speech delay, behavioral abnormalities including hyperactivity and inappropriate laughter, short stature and seizures. The disease is 2q23.1 microdeletion syndrome (Monarch Disease Ontology id MONDO_0016459). Also known as: Del(2)(q23.1), monosomy 2q23.1, pseudo-Angelman syndrome.