15q overgrowth syndrome is a rare partial autosomal trisomy/tetrasomy characterized by facial dysmorphism (long thin face, prominent forehead, down-slanting palpebral fissures, prominent nose with broad nasal bridge, prominent chin), pre- and postnatal overgrowth, renal anomalies (e.g. horseshoe kidney, renal agenesis, hydronephrosis), mild to severe learning difficulties and behavioral abnormalities. Additional features may include craniosynostosis and macrocephaly. The disease is 15q overgrowth syndrome (Monarch Disease Ontology id MONDO_0017806). Also known as: 15q26 overgrowth syndrome.