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Chromosome 17q Partial Duplication - Causes, Symptoms, and Management

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It is a genetic condition caused due to an extra copy of a portion of chromosome 17. Please read the article to know the symptoms and management.

Medically reviewed by

Dr. Rajesh Gulati

Published At March 23, 2023
Reviewed AtMarch 23, 2023

What Is Chromosome 17q Partial Duplication?

Also known as 17q12 duplication syndrome, it is an inherited autosomal dominant condition characterized by intellectual disability, developmental delay, and behavioral changes. The inheritance is dominant because one copy of the duplication in each cell is sufficient to cause the signs and symptoms.

The condition is caused due to an extra copy (duplication) of a portion of chromosome 17. The extent of this duplication determines the severity of the symptoms; some individuals do not have any signs and symptoms, whereas those on the end suffer from seizures, autism spectrum disorder (ASD), schizophrenia, etc.

Diagnosis can be confirmed by genomic testing; treatment includes physical, occupational, and speech therapies, as well as management of the medical condition by the respective specialties.

What Causes Chromosome 17q Partial Duplication?

The human body comprises billions of structural units called cells, continuously replicating themselves (along with the genetic material) to contribute to growth and development. A typical replication synthesizes a new set of genetic material (chromosomes) which then divides to form a daughter cell. Sometimes, due to unexpected mutations (alterations), the replication happens, but the division does not; this condition is known as duplication. Duplication leads to excess genetic material, which is not necessarily desirable; it alters how a genetic trait is expressed. Excess genetic material will synthesize excess proteins, which harms the carefully balanced embryonic developmental process leading to defects.

Individuals with 17q12 duplication or 17q partial duplication have an extra copy of 1.4 million base pairs of DNA (deoxyribonucleic acid) at position q12 on chromosome 17. This might seem a lot, but a regular chromosome 17 has about 83 million base pairs representing three percent of the total DNA in cells. The duplicated segment (the extra 1.4 million base pairs) includes around 15 genes, which code extra proteins leading to intellectual disability, developmental delay, and other disorders associated with 17q12 duplication syndrome.

What Are the Symptoms of 17q Partial Duplication Syndrome?

The following observations have been made in individuals with 17q partial duplication syndrome-

1. Developmental Delay (DD)- DD refers to a child who has not gained the developmental skills expected of him or her compared to others of the same age. Delays in motor function, speech and language, cognitive, play, and social skills may occur. Some of the most common signs of DD are-

  • Learning and developing more slowly than children of the same age.

  • Rolling over, sitting up, crawling, or walking much later than developmentally acceptable.

  • Difficulty communicating or socializing with others.

  • Difficulties talking or talking late.

  • Having problems remembering things.

  • Inability to connect actions with consequences.

  • Trouble learning in school.

  • Inability to do everyday tasks like getting ready for school or using the restroom without help.

2. Intellectual Disability (ID)- The term intellectual disability is usually applied to older children (more than five years) when Intelligent quotient (IQ) testing is valid and reliable. ID involves both cognitive and adaptive or functional abilities.

3. Behavioral And Psychiatric Conditions- This includes individuals with behavioral abnormalities like self-injurious behavior, compulsive disorders, and aggression. Psychiatric complications should be suspected if the patient exhibits signs of autism spectrum disorder (ASD) and schizophrenia.

4. Seizures- This Is a sudden, uncontrolled electrical disturbance in the brain observed in nearly 36 percent of the affected population.

5. Microcephaly- It is a condition where the baby’s head is much smaller than expected. Patients with microcephaly suffer from seizures, DD, ID, feeding problems, etc.,

6. Vision Abnormalities- Commonly seen eye conditions in 17q partial duplication syndrome are coloboma (missing eye tissue), strabismus (malalignment of eyes), amblyopia (lazy eye), astigmatism (error in the shape of the cornea), microphthalmia (small eyes).

7. Growth- A few patients with this syndrome are short-statured, indicating a deficiency in growth hormone.

8. Endocrine Abnormalities- Individuals with 17q partial duplication syndrome are subjected to various hormone deficiencies that lead to type 2 diabetes (insulin deficiency), hyponatremia, growth hormone deficiency, pseudohypoaldosteronism (metabolic disorder), etc.

9. Congenital Heart Conditions- Frequently seen congenital cardiac complication in 17q partial duplication syndrome is a ventral septal defect.

10. Renal Abnormalities- Nearly 20 percent of the affected individuals have renal abnormalities like renal hypoplasia, horseshoe kidney, and renal cysts.

11. Other- This includes a tracheoesophageal fistula and duodenal atresia (underdevelopment of the first part of the duodenum) but is not specific to the syndrome.

How Is 17q Partial Duplication Syndrome Diagnosed?

The symptoms mentioned above are not specific to 17q partial duplication, which makes it difficult to diagnose the condition based on clinical features. The healthcare provider must perform standard evaluations before establishing an initial diagnosis, some of them are-

  • Developmental Assessment- This includes evaluations to establish cognitive impairment, motor delay, speech impairment, etc.

  • Neuropsychiatric Evaluation- This is done to screen the individual for behavioral concerns like ASD, anxiety, sleep disturbances, attention deficit hyperactivity disorder (ADHD), etc.

  • Cardiovascular Assessment- Done with the help of an echocardiogram which helps to detect possible septal defects.

  • Ophthalmologic Evaluation- Helps to assess strabismus, vision, and abnormal ocular involvement.

These evaluations help to establish an initial diagnosis, which can then be confirmed with the help of genomic testing. Chromosomal microarray (a type of genomic testing) is the best method to confirm 17q12 duplication.

How Is 17q Partial Duplication Syndrome Treated?

Since the condition is genetic, the only way to treat it is to manage the signs and symptoms; various therapies and medications are used to achieve this. Some of them are-

  • Occupational, speech, and physical therapy to manage DD after a referral from a developmental pediatrician.

  • Individualized education plan (IEP) to improve cognitive, social, and language delay.

  • Medical conditions should be managed with the help of the concerned specialist.

  • Genetic counseling also plays an important role in managing individuals with 17q partial duplication or 17q12 duplication. It is defined as the process of providing information to the affected individual and their family members about the manner of inheritance, its nature, and its implications. This helps to understand the conditions and prevent them from the next generation through prenatal testing and preimplantation genetic testing.

Conclusion

17q partial duplication or 17q12 duplication syndrome is an inherited genetic condition capable of causing cognitive impairment, DD, and ID. Most cases diagnosed are de novo and need a thorough evaluation and genomic testing before establishing the diagnosis. Treatment is always done with the help of a multidisciplinary team that includes specialists like a developmental pediatrician, physical therapist, cardiologist, speech therapist, ophthalmologist, etc. The prognosis is good if the treatment is started at an early stage.

Dr. Rajesh Gulati
Dr. Rajesh Gulati

Family Physician

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