National Center for Advancing and Translational Sciences Genetic and Rare Diseases Information Center, a program of the National Center for Advancing and Translational Sciences

Ring chromosome 21


Other Names:
Chromosome 21 ring; Ring 21; R21
Categories:
Ring chromosome 21  is a rare chromosome abnormality in which the ends of chromosome 21 join together to form a ring shape. Many people with ring chromosome 21 have normal development and are healthy, having been diagnosed after having chromosome testing due to infertility, multiple miscarriages, or a child with a chromosome abnormality. However, others with ring chromosome 21 have developmental and/or medical problems which can range from mild to severe. This is due to having extra or missing genetic material on the ring chromosome, which can happen when the ring chromosome forms. Signs and symptoms of ring chromosome 21 that may be present can include short stature, delayed puberty in males, small head size, seizures, learning disabilities, underdeveloped sex organs, susceptibility to infections, and/or a variety of birth defects. Some people have signs and symptoms similar to those that occur in people with Down syndrome.[1]

Ring chromosome 21 may be inherited from a parent (typically the mother), or it may occur sporadically (by chance) during the formation of egg or sperm cells or shortly after the egg and sperm join together.[1] A chromosome test of the parents can help determine whether it was inherited and whether future children have an increased chance to have a chromosome abnormality. Treatment for ring chromosome 21 depends on the signs and symptoms present in each person.
Last updated: 6/21/2018

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

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

  • 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 21.

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 21. Click on the link to view a sample search on this topic.

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  1. Ring 21. Unique. 2005; https://www.rarechromo.org/media/information/Chromosome%2021/Ring%2021%20FTNW.pdf.