Ring chromosome 20 syndrome is marked by a characteristic seizure phenotype. Depending on the amount of chromosomal loss and associated mosaicism, ring(20) can be associated with macrocephaly, mild to moderate intellectual deficit, or behavioral problems. In rare cases, brain, kidney or heart malformations may be present. The disease is Monarch Disease Ontology identifier MONDO_0015436 (ring chromosome 20). Also known as: ring chromosome 20 syndrome, ring chromosome type 20.