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Disease Profile

Chromosome 20p deletion

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.


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)

Deletion 20p; Monosomy 20p; 20p deletion;


Chromosome Disorders


Chromosome 20p deletion is a chromosome abnormality that occurs when there is a missing (deleted) copy of genetic material on the short arm (p) of chromosome 20. The severity and the signs and symptoms depend on the size and location of the deletion and which genes are involved. Extremely small deletions (microdeletions) involving the distal end of chromosome 20p are relatively common and in some cases are passed from parent to child without causing any health problems (called a familial variant). In other cases, a 20p deletion causes signs and symptoms such as developmental delay, growth delay, learning difficulties, distinctive facial features, birth defects, and/or various medical problems.[1]

Some 20p deletions are not inherited and occur randomly during the formation of egg or sperm cells, or very early in fetal development. Other 20p deletions are present because a parent has a rearrangement of genetic material on his/her chromosomes. This rearrangement is usually a balanced translocation, which typically does not cause any health problems. Occasionally, a parent has the same deletion as his/her child. Chromosome testing of both parents can provide information about whether the deletion was inherited. If a parent has the same deletion as the child and does not have signs or symptoms, a genetics doctor usually assumes that the 20p deletion is not the cause of the child’s signs and symptoms.[1] Treatment for chromosome 20p deletion is based on the signs and symptoms in each person.

This page is meant to provide general information about 20p deletions. You can contact GARD if you have questions about a specific deletion on chromosome 20p. To learn more about chromosome abnormalities, please visit our GARD webpage on FAQs about Chromosome Disorders.


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

    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

    • Genetics Home Reference (GHR) contains information on Chromosome 20p deletion. 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 20p deletions.

      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 Chromosome 20p deletion. Click on the link to view a sample search on this topic.