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

Chromosome 18p duplication


Other Names:
Duplication 18p; Trisomy 18p; 18p duplication; Duplication 18p; Trisomy 18p; 18p duplication; 18p trisomy; Partial trisomy 18p See More
Categories:
Chromosome 18p duplication is a rare chromosome abnormality in which there are three copies of the short (p) arm of chromosome 18 in each cell, rather than the usual two copies. The severity of the condition and the signs and symptoms depend on the size and location of the duplicated genetic material and which genes are involved.[1][2] A complete duplication of the p arm of chromosome 18 is rare.[3] Reported features include: intellectual disability, foot or hand anomalies, distinctive facial features, and epilepsy.[1][2][3][4] Chromosome 18p duplication may occur sporadically in a family with no previous history or may be inherited from a parent with the same duplication or another chromosome abnormality, such as a balanced translocation.[4] Treatment is based on the signs and symptoms present in each person.[1][2][3]
Last updated: 10/27/2016
The severity of chromosome 18p duplication and the signs and symptoms present depend on the size and location of the duplicated genetic material and which genes are involved. Features commonly include: intellectual disability that ranges from mild to severe, characteristic facial features, and epilepsy. Other findings reported in the medical literature include: hand and foot anomalies, decreased muscle tone (hypotonia), and developmental delay.[1][2][5][3][4]

Some researchers have suggested that several of the cases reported in the medical literature may represent cases in which other chromosome changes are present but are not yet identified. This may help explain the variability in the signs and symptoms present.[2][5] It is additionally suspected that some individuals with chromosome 18p duplication may not be diagnosed if they have mild or absent signs and symptoms and are of normal intelligence.[2]  
Last updated: 10/27/2016

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Showing of 28 |
Medical Terms Other Names
Learn More:
HPO ID
80%-99% of people have these symptoms
Abnormality of the pinna
Abnormally shaped ears
Auricular malformation
Deformed ears
Malformed ears
[ more ] 		0000377
Attention deficit hyperactivity disorder
Attention deficit
Attention deficit disorder
Attention deficit-hyperactivity disorder
Attention deficits
Childhood attention deficit/hyperactivity disorder
[ more ] 		0007018
Bilateral cryptorchidism 0008689
Blepharophimosis
Narrow opening between the eyelids
0000581
Highly arched eyebrow
Arched eyebrows
Broad, arched eyebrows
High, rounded eyebrows
High-arched eyebrows
Thick, flared eyebrows
[ more ] 		0002553
Hypotelorism
Abnormally close eyes
Closely spaced eyes
[ more ] 		0000601
Intellectual disability, mild
Mental retardation, borderline-mild
Mild and nonprogressive mental retardation
Mild mental retardation
[ more ] 		0001256
Midface retrusion
Decreased size of midface
Midface deficiency
Underdevelopment of midface
[ more ] 		0011800
Polyphagia
Voracious appetite
0002591
Preauricular skin tag 0000384
Pyloric stenosis 0002021
Sloping forehead
Inclined forehead
Receding forehead
[ more ] 		0000340
Telecanthus
Corners of eye widely separated
0000506
Thin vermilion border
Decreased volume of lip
Thin lips
[ more ] 		0000233
Underdeveloped nasal alae
Underdeveloped tissue around nostril
0000430
Upslanted palpebral fissure
Upward slanting of the opening between the eyelids
0000582
Wide nasal bridge
Broad nasal bridge
Broad nasal root
Broadened nasal bridge
Increased breadth of bridge of nose
Increased breadth of nasal bridge
Increased width of bridge of nose
Increased width of nasal bridge
Nasal bridge broad
Wide bridge of nose
Widened nasal bridge
[ more ] 		0000431
30%-79% of people have these symptoms
Abnormality of finger
Abnormalities of the fingers
0001167
Abnormality of the foot
Abnormal feet morphology
Abnormality of the feet
Foot deformities
Foot deformity
[ more ] 		0001760
Narrow mouth
Small mouth
0000160
5%-29% of people have these symptoms
Abnormality of cardiovascular system morphology 0030680
Facial palsy
Bell's palsy
0010628
High, narrow palate
Narrow, high-arched roof of mouth
Narrow, highly arched roof of mouth
[ more ] 		0002705
Intrauterine growth retardation
Prenatal growth deficiency
Prenatal growth retardation
[ more ] 		0001511
Microcephaly
Abnormally small skull
Decreased circumference of cranium
Decreased size of skull
Reduced head circumference
Small head circumference
[ more ] 		0000252
Micrognathia
Little lower jaw
Small jaw
Small lower jaw
[ more ] 		0000347
Neonatal hypotonia
Low muscle tone, in neonatal onset
0001319
Short stature
Decreased body height
Small stature
[ more ] 		0004322
Showing of 28 |
Last updated: 7/1/2020
Because the presence and severity of signs and symptoms vary from person to person, treatment also varies. If an intellectual disability and/or developmental delay is present, early educational intervention and early services are important.

It is essential to work with one's person's health care provider and medical team to determine the appropriate medical management plan.
Last updated: 10/27/2016

Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Patient Registry

  • A registry supports research by collecting of information about patients that share something in common, such as being diagnosed with Chromosome 18p duplication. The type of data collected can vary from registry to registry and is based on the goals and purpose of that registry. Some registries collect contact information while others collect more detailed medical information. Learn more about registries.

    Registries for Chromosome 18p duplication:
    Chromosome 18 Registry & Research Society
     

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

  • The National Human Genome Research Institute, part of the National Institutes of Health (NIH), has developed a fact sheet on chromosome abnormalities, which may be helpful to you. To read this information, visit the link.

    MedlinePlus, the National Library of Medicine Web site designed to direct you to information and resources that help you research your health questions, provides further information about chromosomes. Click on the link.
  • Genetics Home Reference (GHR) contains information on Chromosome 18p duplication. This website is maintained by the National Library of Medicine.

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 18p duplication. Click on the link to view a sample search on this topic.

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know. Submit a new question

  • What are some of the signs or symptoms associated with trisomy 18p? What are some of the behavioural characteristics of this syndrome if any? What are some treatment options for an adolescent with this syndrome, ASD (autism spectrum disorder), and no intellectual disability displaying challenging behaviours? See answer


  1. Rodríguez L, Liehr T, Mrasek K, Mansilla E, Martínez-Fernández ML, Garcia A, Martínez-Frías ML. Small Supernumerary Chromosome Marker Generating Complete and Pure Trisomy 18p, Characterized by Molecular Cytogenetic Techniques and Review. American Journal of Medical Genetics Part A. 2007; 143A(22):2727-2732. https://www.ncbi.nlm.nih.gov/pubmed/17937429.
  2. Mabboux P, Brisset S, Aboura A, Pineau D, Kourbi V, Joannidis S et al. Pure and Complete Trisomy 18p Due to a Supernumerary Marker Chromosome Associated with Moderate Mental Retardation. American Journal of Medical Genetics Part A. 2007; 143A(7):727-733. https://www.ncbi.nlm.nih.gov/pubmed/17330860.
  3. Azoospermia and trisomy 18p syndrome: a fortuitous association? A patient report and a review of the literature. Guillaume Jedraszak, Henri Copin, Manuel Demailly, Catherine Quibel, Thierry Leclerc, Marlène Gallet, Moncef Benkhalifa, Aline Receveur. Molecular cytogenetics. June 4. 2015; 8(34):https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4453045/.
  4. Orendi K, Uhrig S, Mach M, Tschepper P, Speicher MR. Complete and pure trisomy 18p due to a complex chromosomal rearrangement in a male adult with mild intellectual disability.. American Journal of Medical Genetics (Part A). May 21, 2013; 161A(7):1806-1812. https://www.ncbi.nlm.nih.gov/pubmed/23695988.
  5. Schinzel A. Catalogue of Unbalanced Chromosome Aberrations in Man. New York: Walter de Gruyter; 2001;