Rare Ophthalmology News

Disease Profile

Chromosome 1q21.1 duplication syndrome

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 / 1 000 000

< 331

US Estimated

< 514

Europe Estimated

Age of onset

Infancy

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ICD-10

Q92.3

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.

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)

1q21.1 microduplication syndrome

Categories

Chromosome Disorders; Congenital and Genetic Diseases

Summary

1q21.1 microduplication is a chromosomal change in which a small amount of genetic material on chromosome 1 is abnormally copied (duplicated). The duplication occurs on the long (q) arm of the chromosome at a location designated q21.1. 

Some people with a 1q21.1 microduplication have developmental delay and intellectual disability that is typically mild to moderate. Individuals with this condition can also have features of autism spectrum disorder. These disorders are characterized by impaired communication and socialization skills, as well as delayed development of speech and language. Expressive language skills (vocabulary and the production of speech) tend to be more impaired than receptive language skills (the ability to understand speech) in affected individuals. In childhood, 1q21.1 microduplications may also be associated with an increased risk of attention-deficit/hyperactivity disorder (ADHD) and other behavioral problems. Psychiatric disorders such as schizophrenia or mood disorders such as anxiety or depression occur in some affected individuals, usually during adulthood. Rarely, recurrent seizures (epilepsy) occur in people with a 1q21.1 microduplication. 

Some individuals with a 1q21.1 microduplication are born with malformations of the heart, including a particular combination of heart defects known as tetralogy of Fallot. Less commonly, other physical malformations such as the urethra opening on the underside of the penis (hypospadias) in males, inwardand upward-turning feet (clubfeet), or misalignment of the hip joint (hip dysplasia) are present at birth. Individuals with a 1q21.1 microduplication may also have a larger than average head size or taller than average adult stature. Some have slightly unusual facial features such as wide-set eyes or low-set ears. As adults, individuals with a 1q21.1 microduplication may be prone to develop cysts, swollen and knotted (varicose) veins, or carpal tunnel syndrome, which is characterized by numbness, tingling, and weakness in the hands and fingers. However, there is no particular pattern of physical abnormalities that characterizes 1q21.1 microduplications. Signs and symptoms related to the chromosomal change vary even among affected members of the same family. Some people with the duplication have no identified physical, intellectual, or behavioral abnormalities.

This disease summary is from MedlinePlus Genetics, an online health information resource from the National Institutes of Health.

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
Global developmental delay
0001263
Intellectual disability
Mental deficiency
Mental retardation
Mental retardation, nonspecific
Mental-retardation

[ more ]

0001249
30%-79% of people have these symptoms
Frontal bossing
0002007
Hypertelorism
Wide-set eyes
Widely spaced eyes

[ more ]

0000316
Macrocephaly
Increased size of skull
Large head
Large head circumference

[ more ]

0000256
5%-29% of people have these symptoms
Arthrogryposis multiplex congenita
0002804
Attention deficit hyperactivity disorder
Attention deficit
Attention deficit disorder
Attention deficit-hyperactivity disorder
Attention deficits
Childhood attention deficit/hyperactivity disorder

[ more ]

0007018
Autism
0000717
Cataract
Clouding of the lens of the eye
Cloudy lens

[ more ]

0000518
Cryptorchidism
Undescended testes
Undescended testis

[ more ]

0000028
Failure to thrive
Faltering weight
Weight faltering

[ more ]

0001508
Gastroesophageal reflux
Acid reflux
Acid reflux disease
Heartburn

[ more ]

0002020
Glaucoma
0000501
Hallucinations
Hallucination
Sensory hallucination

[ more ]

0000738
Hip dislocation
Dislocated hips
Dislocation of hip

[ more ]

0002827
Hip dysplasia
0001385
Hydrocephalus
Too much cerebrospinal fluid in the brain
0000238
Hypertonia
0001276
Hypospadias
0000047
Intellectual disability, mild
Mental retardation, borderline-mild
Mild and nonprogressive mental retardation
Mild mental retardation

[ more ]

0001256
Muscular hypotonia
Low or weak muscle tone
0001252
Schizophrenia
0100753
Seizure
0001250
Strabismus
Cross-eyed
Squint
Squint eyes

[ more ]

0000486
Talipes equinovarus
Club feet
Club foot
Clubfeet
Clubfoot

[ more ]

0001762
Tetralogy of Fallot
0001636
Percent of people who have these symptoms is not available through HPO
Autosomal dominant inheritance
0000006
Hypoplasia of the corpus callosum
Underdevelopment of part of brain called corpus callosum
0002079
Incomplete penetrance
0003829
Specific learning disability
0001328
Sporadic
No previous family history
0003745

Cause

Chromosome 1q21.1 duplication syndrome can occur sporadically (by chance) from a de novo mutation or can be inherited in an autosomal dominant manner from a parent that has the same duplication. When the condition occurs sporadically, it is caused by a random error during the formation of the egg or sperm cell, or during the early days after fertilization.[1] The duplication occurs when part of chromosome 1 is copied (duplicated) abnormally, resulting in the extra genetic material from the duplicated segment.[2] If the condition is inherited from a parent, it means that one of the parents also has the extra piece of genetic material. In these cases, the parent with the duplication has a 50% chance with each pregnancy to pass the duplication on to his/her child. The only way to know if it has been inherited from a parent is for the parents to have genetic testing. A parent with the duplication may not have any signs or symptoms. In both cases, nothing that either parent does, or does not do, can cause this syndrome to occur.

Individuals who are interested in genetic testing for themselves or family members should speak with a genetics professional.

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 Genetics contains information on Chromosome 1q21.1 duplication syndrome. 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 1q21.1 microduplications.

      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.
      • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
      • 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 1q21.1 duplication syndrome. Click on the link to view a sample search on this topic.

        Selected Full-Text Journal Articles

          References

          1. 1q21.1 Microduplications. Unique. June 2011; https://www.rarechromo.org/information/Chromosome%20%201/1q21.1%20microduplications%20FTNW.pdf. Accessed 8/15/2013.
          2. Chromosomal duplication. Genetics Home Reference. August 12, 2013; https://ghr.nlm.nih.gov/handbook/illustrations/chromosomalduplication. Accessed 8/15/2013.
          3. Hamoush A. Chromosome 1q21.1 duplication syndrome. OMIM. June 10, 2009; https://www.ncbi.nlm.nih.gov/omim/612475. Accessed 11/4/2010.

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