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Disease Profile

Trisomy 18

Prevalence
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.
1-9 / 1 000 000

331 - 2,979

US Estimated

1-9 / 1 000 000

514 - 4,622

Europe Estimated

Age of onset

Neonatal

ICD-10

Q91.0 Q91.1 Q91.2 Q91.3

Inheritance

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

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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

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X-linked
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.

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

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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.

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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.

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Not applicable

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Other names (AKA)

Chromosome 18 trisomy; 18 trisomy; Edwards syndrome;

Categories

Congenital and Genetic Diseases; Digestive Diseases; Eye diseases;

Summary

Trisomy 18 is a chromosome disorder characterized by having 3 copies of chromosome 18 instead of the usual 2 copies. Signs and symptoms include severe intellectual disability; low birth weight; a small, abnormally shaped head; a small jaw and mouth; clenched fists with overlapping fingers; congenital heart defects; and various abnormalities of other organs. Trisomy 18 is a life-threatening condition; many affected people die before birth or within the first month of life. Some children have survived to their teenage years, but with serious medical and developmental problems. Most cases are not inherited and occur sporadically (by chance).[1][2]

Symptoms

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.

Medical Terms Other Names
Learn More:
HPO ID
80%-99% of people have these symptoms
Atrial septal defect
An opening in the wall separating the top two chambers of the heart
Hole in heart wall separating two upper heart chambers

[ more ]

0001631
Broad forehead
Increased width of the forehead
Wide forehead

[ more ]

0000337
Cachexia
Wasting syndrome
0004326
Camptodactyly of finger
Permanent flexion of the finger
0100490
Cognitive impairment
Abnormality of cognition
Cognitive abnormality
Cognitive defects
Cognitive deficits
Intellectual impairment
Mental impairment

[ more ]

0100543
Cryptorchidism
Undescended testes
Undescended testis

[ more ]

0000028
Deviation of finger
Atypical position of finger
Finger pointing in a different direction than usual

[ more ]

0004097
Dolichocephaly
Long, narrow head
Tall and narrow skull

[ more ]

0000268
Global developmental delay
0001263
High forehead
0000348
Hypertelorism
Wide-set eyes
Widely spaced eyes

[ more ]

0000316
Hypertonia
0001276
Intrauterine growth retardation
Prenatal growth deficiency
Prenatal growth retardation

[ more ]

0001511
Low-set, posteriorly rotated ears
0000368
Microretrognathia
Small retruded chin
0000308
Muscular hypotonia
Low or weak muscle tone
0001252
Narrow face
Decreased breadth of face
Decreased width of face

[ more ]

0000275
Narrow mouth
Small mouth
0000160
Narrow palate
Narrow roof of mouth
0000189
Narrow pelvis bone
0003275
Omphalocele
0001539
Pointed helix
Spock's ear
0100810
Prominent occiput
Prominent back of the skull
Prominent posterior skull

[ more ]

0000269
Short nose
Decreased length of nose
Shortened nose

[ more ]

0003196
Short stature
Decreased body height
Small stature

[ more ]

0004322
Triangular face
Face with broad temples and narrow chin
Triangular facial shape

[ more ]

0000325
Underdeveloped supraorbital ridges
Flattened bony protrusion above eyes
0009891
Ventricular septal defect
Hole in heart wall separating two lower heart chambers
0001629
30%-79% of people have these symptoms
Abnormal morphology of female internal genitalia
0000008
Abnormal toenail morphology
Abnormality of the toenail
Abnormality of the toenails

[ more ]

0008388
Abnormality of the fontanelles or cranial sutures
0000235
Abnormality of the hip bone
Abnormality of the hips
0003272
Anal atresia
Absent anus
0002023
Bilateral single transverse palmar creases
0007598
Blepharophimosis
Narrow opening between the eyelids
0000581
Choanal atresia
Blockage of the rear opening of the nasal cavity
Obstruction of the rear opening of the nasal cavity

[ more ]

0000453
Cleft palate
Cleft roof of mouth
0000175
Congenital diaphragmatic hernia
0000776
Delayed skeletal maturation
Delayed bone maturation
Delayed skeletal development

[ more ]

0002750
Epicanthus
Eye folds
Prominent eye folds

[ more ]

0000286
Esophageal atresia
Birth defect in which part of esophagus did not develop
0002032
Hydronephrosis
0000126
Microcephaly
Abnormally small skull
Decreased circumference of cranium
Decreased size of skull
Reduced head circumference
Small head circumference

[ more ]

0000252
Non-midline cleft lip
0100335
Oligohydramnios
Low levels of amniotic fluid
0001562
Webbed neck
Neck webbing
0000465
5%-29% of people have these symptoms
Abnormality of retinal pigmentation
0007703
Abnormality of the lower limb
Lower limb deformities
0002814
Abnormality of the ribs
Rib abnormalities
0000772
Anencephaly
0002323
Aplasia/Hypoplasia of the corpus callosum
0007370
Arnold-Chiari malformation
0002308
Cataract
Clouding of the lens of the eye
Cloudy lens

[ more ]

0000518
Cyclopia
Cyclops eye
Single central eye

[ more ]

0009914
Glaucoma
0000501
Holoprosencephaly
0001360
Iris coloboma
Cat eye
0000612
Microcornea
Cornea of eye less than 10mm in diameter
0000482
Microphthalmia
Abnormally small eyeball

Cause

In most cases, trisomy 18 is caused by having 3 copies of chromosome 18 in each cell in the body, instead of the usual 2 copies. The extra genetic material from the 3rd copy of the chromosome disrupts development, causing the characteristic signs and symptoms of the condition.

About 5% of people with trisomy 18 have 'mosaic trisomy 18' (when there is an extra copy of the chromosome in only some of the body's cells). The severity of mosaic trisomy 18 depends on the number and locations of cells with the extra copy.

Very rarely, an extra piece of chromosome 18 is attached to another chromosome; this is called translocation trisomy 18, or partial trisomy 18. If only part of the long (q) arm of chromosome 18 is present in 3 copies, the features may be less severe than in people with full trisomy 18.[1]

Organizations

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

    • MedlinePlus was designed by the National Library of Medicine to help you research your health questions, and it provides more information about this topic.
    • Genetics Home Reference (GHR) contains information on Trisomy 18. This website is maintained by the National Library of Medicine.
    • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

      In-Depth Information

      • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
      • The Merck Manual for health care professionals provides information on Trisomy 18.
      • 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 Trisomy 18. Click on the link to view a sample search on this topic.

        References

        1. Trisomy 18. Genetics Home Reference. March, 2013; https://ghr.nlm.nih.gov/condition/trisomy-18. Accessed 8/23/2015.
        2. Haldeman-Englert C. Trisomy 18. MedlinePlus. August 2011; https://www.nlm.nih.gov/medlineplus/ency/article/001661.htm. Accessed 1/17/2012.
        3. Trisomy 18. Genetics Home Reference (GHR). January 2009; https://ghr.nlm.nih.gov/condition/trisomy-18. Accessed 1/17/2012.

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