Monarch Disease Ontology term MONDO_0013266 (neurodevelopmental disorder with hypotonia, stereotypic hand movements, and impaired language) is any autosomal dominant non-syndromic intellectual disability in which the cause of the disease is a mutation in the MEF2C gene. Also known as: MEF2C Deficiency, MEF2C autosomal dominant non-syndromic intellectual disability, MEF2C haploinsufficiency syndrome (MCHS), MEF2C-related neurodevelopmental disorder, MEF2C-related syndrome, MRD20, autosomal dominant mental retardation 20, autosomal dominant non-syndromic intellectual disability caused by mutation in MEF2C.