Rare Psychiatry News

Disease Profile

Ring chromosome 20

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.

<1 / 1 000 000

US Estimated

Europe Estimated

Age of onset






Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

Chromosome 20 ring; Ring 20; R20;


Chromosome Disorders; Congenital and Genetic Diseases; Nervous System Diseases


Ring chromosome 20 is a chromosome abnormality that affects the development and function of the brain. People with ring chromosome 20 often have recurrent seizures or epilepsy. Other symptoms might include intellectual disability, behavioral difficulties, growth delay, short stature, a small head (microcephaly), and characteristic facial features. Ring chromosome 20 is caused by an abnormal chromosome known as a ring chromosome 20 or r(20). A ring chromosome is a circular structure that occurs when a chromosome breaks in two places and its broken ends fuse together. Ring chromosome 20 is usually not inherited. It almost always occurs by chance during the formation of reproductive cells (eggs or sperm) or in early embryonic development.[1] Treatment for ring chromosome 20 is focused on management of seizures and accommodations for learning.[2]


Treatment of ring chromosome 20 is typically focused on management of seizures. The seizures associated with ring chromosome 20 do not generally respond well to medications. The treatment that is successful varies from person to person. ‘Broad spectrum’ anti-epileptic drugs are usually tried first since they are active against different seizure types. Examples include valproate, levetiracetam, lamotrigine, topiramate and zonisamide. Success has been reported in some people with a combination of valproate and lamotrigine, but so far no single therapy has worked for everyone. 

Vagus nerve stimulation
 (VNS) has been tried and a reduction in seizures has been
reported in some cases but not in others. This involves implanting a medical device
under the skin, similar to a pacemaker that delivers a mild electrical current to the brain via the vagus nerve. The long-term effectiveness of VNS therapy is not yet known.[2]


Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

    Organizations Providing General Support

      Learn more

      These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

      Where to Start

      • The Epilepsy Foundation provides information on Ring chromosome 20.
      • Genetics Home Reference (GHR) contains information on Ring chromosome 20. This website is maintained by the National Library of Medicine.
      • Unique is a source of information and support to families and individuals affected by rare chromosome disorders. Click on the link to view information about ring chromosome 20.

        In-Depth Information

        • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
        • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
        • PubMed is a searchable database of medical literature and lists journal articles that discuss Ring chromosome 20. Click on the link to view a sample search on this topic.


          1. Ring Chromosome 20 Syndrome. Genetics Home Reference. May 2009; https://ghr.nlm.nih.gov/condition/ring-chromosome-20-syndrome.
          2. Ring 20. Unique. 2014; https://www.rarechromo.org/information/Chromosome%2020/Ring%2020%20FTNW.pdf.

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