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17q12 duplication
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

17q12 duplication

17q12 duplication is a chromosomal change where a segment of chromosome 17 is abnormally copied, leading to a wide range of signs and symptoms from none to intellectual disability and physical abnormalities.

Overview

17q12 duplication is a chromosomal change in which a small piece of chromosome 17 is copied (duplication) abnormally in each cell. The duplication occurs on the long (q) arm of the chromosome at a position designated q12.

Signs and symptoms related to 17q12 duplications vary significantly, even among members of the same family. Some individuals with the duplication have no apparent signs or symptoms, or the features are very mild. Other individuals can have intellectual disability, delayed development, and a wide range of physical abnormalities.

Intellectual and learning ability in people with 17q12 duplications ranges from normal to severely impaired. Many affected individuals have delayed development, particularly involving speech and language skills and gross motor skills such sitting, standing, and walking. Seizures are also common. Neurodevelopmental and psychiatric conditions that have been reported in people with 17q12 duplications include autism spectrum disorder (which affects social interaction and communication), schizophrenia, aggression, and self-injury. About half of affected individuals have an unusually small head.

Less commonly, 17q12 duplications have been associated with abnormalities of the eyes, heart, kidneys, and brain. Some individuals with this chromosomal change have subtle differences in facial features, although these are not consistent.

Frequency

17q12 duplications appear to be uncommon. Several dozen people with this chromosomal change have been described in the medical literature.

Causes & Risk Factors

Most people with 17q12 duplications have an extra copy of about 1.4 million DNA building blocks (base pairs), also written as 1.4 megabases (Mb), at position q12 on chromosome 17. This duplication affects one of the two copies of chromosome 17 in each cell.

The duplicated segment is surrounded by short, repeated sequences of DNA that make the segment prone to rearrangement during meiosis. The rearrangement can lead to deletion or duplication copies of DNA at 17q12. (A missing copy of this segment causes a related chromosomal condition called 17q12 deletion syndrome.)

The segment of 17q12 that is most commonly duplicated includes at least 15 genes. It is unclear which of these genes, when present in more than one copy, contribute to intellectual disability, delayed development, and the other signs and symptoms described above. Because some people with a 17q12 duplication have no obvious intellectual or physical problems, researchers suspect that additional genetic factors may influence whether a person has signs and symptoms related to the chromosomal change.

Associated Chromosome

  • chromosome 17

Inheritance

17q12 duplications have an autosomal dominant pattern of inheritance, which means one copy of the duplication in each cell is sufficient to cause the signs and symptoms.

Most 17q12 duplications are inherited. In these cases, the parent most often has only mild signs and symptoms or no related features at all. Less commonly, 17q12 duplications represent a de novo and occur in people with no history of the duplication in their family.

Other Names

  • 17q12 duplication syndrome
  • 17q12 microduplication
  • 17q12 microduplication syndrome
  • 17q12 recurrent duplication
  • Chromosome 17q12 duplication syndrome
  • Recurrent duplication of 17q12

Frequently Asked Questions

Clinicians often look for a combination of developmental delays, particularly in speech and language acquisition and gross motor skills such as sitting, standing, and walking. Other frequent indicators include the presence of seizures, a smaller than average head circumference (microcephaly), and behavioral issues such as autism spectrum disorder traits or aggression. Because physical features can be subtle or absent, a pattern of unexplained developmental regression or delay is a key trigger for genetic testing.
The standard diagnostic method is a chromosomal microarray (CMA), also known as array comparative genomic hybridization (aCGH), which can detect small duplications and deletions across the genome. If a CMA is negative but clinical suspicion remains high, whole exome sequencing or whole genome sequencing may be considered to identify smaller structural variants. Patients should discuss with their geneticist whether a CMA is the appropriate first-line test given their specific symptoms.
This condition exhibits variable expressivity, meaning the same genetic change can result in a wide spectrum of clinical outcomes. Factors such as the exact size of the duplicated segment, the specific genes included in that segment, and the presence of other genetic modifiers or environmental factors can influence the severity of symptoms. Consequently, it is common for one family member to have normal development while another sibling or parent experiences intellectual disability or speech delays.
Yes, the duplication can be inherited in an autosomal dominant pattern, meaning a child can inherit it from a parent who may be asymptomatic or have mild symptoms. It can also arise de novo, meaning it occurs as a new mutation in the child without being present in either parent. Genetic counseling is essential to determine the origin of the duplication, assess the recurrence risk for future pregnancies, and discuss options such as preimplantation genetic testing or prenatal diagnosis.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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