2q23.1 microduplication syndrome is a rare chromosomal anomaly syndrome, resulting from the partial duplication of the long arm of chromosome 2, primarily characterized by global developmental delay, hypotonia, autistic-like features and behavioral problems. Craniofacial dysmorphism (arched eyebrows, hypertelorism, bilateral ptosis, prominent nose, wide mouth, micro/retrognathia) and an affable personality are also commonly associated. Minor digital anomalies (fifth finger clinodactyly and large, broad first toe) have occasionally been reported. The disease is Monarch Disease Ontology term MONDO_0017786 (2q23.1 microduplication syndrome). Also known as: dup(2)(q23.1), trisomy 2q23.1.