What are the other Names for this Condition? (Also known as/Synonyms)

• 17q12 Microduplication Syndrome

What is Chromosome 17q12 Microduplication Syndrome? (Definition/Background Information)

• Chromosome 17q12 Microduplication Syndrome is a rare condition caused by the presence of an extra copy of a small piece of chromosome 17 in the cells of the body. This condition can occur sporadically as a de novo mutation or can be inherited from one’s parents. The syndrome may be diagnosed through specialized genetic testing
• The signs and symptoms of Chromosome 17q12 Microduplication Syndrome can vary widely among affected individuals. Some individuals have no symptoms, while others may have features such as mild to moderate developmental delay and learning difficulties, feeding issues, and seizures
• Following a diagnosis, the condition may be managed based on the presenting symptoms and extent of involvement of the body systems. The treatment may involve physician experts from several specialties, and can include seizure control, physiotherapy, and surgery for correction of physical defects, if necessary
• The prognosis is primarily dependent on the severity of the disorder, and it varies from one child to another. Most of the affected children with Chromosome 17q12 Microduplication Syndrome are able to cope well through adequate treatment and supportive care. Some of the abnormalities are known to improve with time

Who gets Chromosome 17q12 Microduplication Syndrome? (Age and Sex Distribution)

• Chromosome 17q12 Microduplication Syndrome is a rare congenital disorder, and only about 20 cases have been reported
• The presentation of symptoms may occur at or following the birth of the child
• In many cases, individuals with mild signs and symptoms may be undiagnosed in their lifetime. Hence, a true incidence of the disorder may be difficult to estimate
• Both males and females are equally affected
• Worldwide, individuals of all racial and ethnic groups may be affected

What are the Risk Factors for Chromosome 17q12 Microduplication Syndrome? (Predisposing Factors)

In a vast majority of individuals, there are no identified risk factors for Chromosome 17q12 Microduplication Syndrome.

• A positive family history may be an important risk factor, since 17q12 Microduplication Syndrome can be inherited
• Currently, no environmental and lifestyle (including dietary) factors have been implicated
• The syndrome is not caused by what the expectant mother does or does not do, either prior to or during pregnancy

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Chromosome 17q12 Microduplication Syndrome? (Etiology)

Chromosome 17q12 Microduplication Syndrome is caused by an extra copy of genetic material on the long arm (q) of chromosome 17. The amount of chromosome material added/duplicated is very small and the condition may be diagnosed only using highly specialized and sensitive molecular testing.

• Most cases of the disorder develop sporadically (de novo) during embryonic development. This means that no duplication of genetic material at 17q12 is observed in either of the parents. When the condition is inherited, it occurs in an autosomal dominant manner
• There are two chromosomes numbered 17. Children with 17q12 Microduplication Syndrome typically will have one (chromosome 17) in normal condition, while the other is abnormal. The abnormality is characterized by a gain of chromosomal material
• Individuals with this disorder may present many similar signs and symptoms. However, even though the amount duplicated in this disorder is tiny, there may still be some differing signs and symptoms

It is important to note that a child’s development and future is not only influenced by the chromosome material duplicated/deleted and genes involved, but also by other factors such as one’s environment, involvement of other genes, and unique personality.

Additional (general) information on chromosomes, which is helpful in understanding the disorder:

Chromosomes are microscopic thread-like protein structures present in each cell nucleus that carry genetic information in the form of DNA (deoxyribonucleic acid). DNAs are nucleic acids that encodes the genetic information of any organisms; a basic unit of the DNA is termed a gene with a specific set of instructions and a defined function. Each chromosome is “X” shaped with a center, called the centromere, and two short arms (termed p arms) and two long arms (termed q arms).

Humans have 46 chromosomes in the cell nucleus, in 23 pairs, of which one pair is named the sex chromosome. In males, it is designated XY, for chromosome X and chromosome Y; while, in females, it is designated XX, for a pair of chromosome X. The other 22 pairs of chromosomes are numbered chromosome 1 through 22, approximately according to size (with chromosome 1 being the largest; chromosome 21 being the smallest) and are referred to as autosomes or somatic chromosomes. During conception, the embryo inherits one copy of each chromosome from each parent (i.e., mother and father). Any alteration in the chromosome numbers or structure, such as via addition or deletion of chromosomal material, can result in mild to severe genetic abnormalities that may manifest as birth defects, growth delays, and intellectual disabilities.

A chromosome duplication disorder indicates that a certain portion of the chromosomal material is duplicated, which may be detected through molecular genetic testing. Depending on the nature and amount of extra material, the manifestation of a set of signs and symptoms are noted.

What are the Signs and Symptoms of Chromosome 17q12 Microduplication Syndrome?

The signs and symptoms of Chromosome 17q12 Microduplication Syndrome may be different from one individual to another. The degree of signs and symptoms are often related to the amount of chromosome material gained and the number of genes affected. Nevertheless, many individuals with this microduplication syndrome have very mild presentations with no major birth defects being observed.

The commonly noted signs and symptoms of Chromosome 17q12 Microduplication Syndrome include:

• Development delays may be mild
• Feeding difficulties due to swallowing difficulties, vomiting, and gastroesophageal reflux disease
• Constipation may be occasionally noted
• Gross and fine motor skills may be affected in a minor way
• Minor hand and foot abnormalities may be noted
• Seizures may be observed
• Speech and learning disabilities (including communication difficulties) that may be mild, moderate, or rarely, severe
• Behavioral issues in some cases
• Minor hearing and vision impairment
• Mild sleep disturbances that can affect one’s physical and mental health

Children are healthy in most cases, and the life expectancy is also reported to be normal.

How is Chromosome 17q12 Microduplication Syndrome Diagnosed?

Children can have varying signs and symptoms. Some children with mild signs and symptoms may go undiagnosed in their lifetimes. Given the rarity of the condition, the healthcare provider should have a high index of suspicion to consider 17q12 Microduplication Syndrome in the differential diagnosis. Often, specialized tests are necessary to confirm the disorder.

Chromosome 17q12 Microduplication Syndrome is diagnosed on the basis of the following information:

• Complete physical examination and thorough medical history evaluation, including family medical history
• Assessment of the presenting signs and symptoms, including evaluation of body systems such as vision, hearing, muscles, heart, kidneys, central nervous system, genitalia, and immune system
• Hearing and vison assessment through various tests
• Evaluation of heart defects
• Laboratory tests, as needed, such as electrolyte levels, serum calcium levels, thyroid function test, kidney function test, urine tests, sex hormone studies, etc.
• Radiological studies of the affected regions, as needed
• Kidney and urinary tract scans, as needed
• Brain scans: These may include prenatal ultrasounds and MRI scans, and CT/MRI scans after development of the child
• Neurological examination that involves the central nervous system (brain and spinal cord)
• Behavioral studies
• Prenatal studies including abdominal ultrasonography
• Specialized genetic testing techniques are often required to confirm the diagnosis. This may include:
  • Fluorescence in situ hybridization (FISH) testing
  • Array comparative genomic hybridization (array-CGH)
  • DNA sequencing

Often, karyotyping of the chromosome is not adequate to diagnose the condition, since individuals with this condition can have normal karyotype chromosomal studies.

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Chromosome 17q12 Microduplication Syndrome?

The complications of Chromosome 17q12 Microduplication Syndrome may include:

• Severe emotional stress for parents and caregivers
• Some pregnancy complications may be observed
• Failure to thrive
• Delayed milestone achievement that may affect when a child rolls, sits, crawls, or walks
• Poor growth due to malnutrition caused by weak suckling
• Risk of falls and injury due to seizures
• Self-injurious behavior (rarely)
• Kidney anomalies
• Reduced quality of life

Complications may occur with or without treatment, and in some cases, due to treatment also.

How is Chromosome 17q12 Microduplication Syndrome Treated?

There is no cure for Chromosome 17q12 Microduplication Syndrome since it is a genetic condition. The treatment is usually given to manage the signs and symptoms and any complication that develops. It also depends on the severity of the signs and symptoms and the body systems affected. Individuals with mild signs and symptoms may require periodic monitoring without significant medical intervention. Often, a multidisciplinary team of specialists including pediatricians, ophthalmologists, otolaryngologists, neurologists, internists, cardiologists, endocrinologists, surgeons, and other healthcare professionals are involved in managing the condition.

The treatment measures for 17q12 Microduplication Syndrome may involve:

• Use of hearing aids
• Seizure control using anticonvulsant medication, vitamin supplements, and ketogenic diet
• Employing suitable learning strategies via music therapy, visual and tactile books, learning through fun and play, and lots of repetition. Writing by holding a pencil may be very difficult; but touchscreen computers and keyboards are known to be easier to use and learn
• Speech and language therapy; the use of sign language may be beneficial; rectification of hearing impairment may improve speech and language development
• Physiotherapy for weakened muscles, including incorporating daily exercise regimen
• Development of motor skills via daily exercises, swimming, hydrotherapy, and other adapted activities; use of specially-designed toys and daily-used items (such as spoons and cups)
• For feeding difficulties, use of feeding tubes (temporary nasogastric or gastrostomy tubes), medications, feed thickeners, bottle-feeding expressed milk, including special diets and nutritional supplements
• A surgical procedure named fundoplication may be necessary in some children with severe GERD. Milder GERD cases can be generally well-controlled by giving feeds slowly and positioning the baby in a semi-upright. And, where necessary, raising the head of the end of the bed for sleeping is also recommended
• Surgical correction of physical defects, as assessed by a healthcare expert
• Use of suitable glasses and surgical rectification of vision defects, if necessary
• Sleep disorders may require medication; daytime naps may be advised
• Psychotherapy, behavior modification, and establishing discipline techniques, as necessary
• Social skills training support groups and exercises
• Occupational therapy

Regular medical screening at periodic intervals with tests and physical examinations are necessary and highly recommended.

How can Chromosome 17q12 Microduplication Syndrome be Prevented?

Chromosome 17q12 Microduplication Syndrome may not be preventable since many of these genetic disorders are diagnosed at or following the birth of the child. A majority of cases are sporadic occurrences, which means there is no family history of the condition.

In some rare cases, the condition may be familial, meaning they occur within families. In expecting parents with a familial history:

• Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy), if available, may help in understanding the risks better during pregnancy
• If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
• Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders

It is important to note that the chances of both the parents with normal chromosomes having another child with Chromosome 17q12 Microduplication Syndrome is highly unlikely. This may be confirmed via specialized prenatal testing and preimplantation genetic diagnosis (PGD), if needed. Prenatal tests may include chorionic villus sampling (CVS) and amniocentesis.

What is the Prognosis of Chromosome 17q12 Microduplication Syndrome? (Outcomes/Resolutions)

The prognosis of Chromosome 17q12 Microduplication Syndrome is dependent upon the severity of the signs and symptoms and associated complications, if any. It may be assessed on a case-by-case basis, although the long-term outlook is generally reported to be favorable.

• Children with mild conditions are generally able to cope well via appropriate treatment and adaptive behaviors as they get older
• Some of the abnormalities are known to resolve or improve with time
• Some children may rarely require lifelong medical support and care

Additional and Relevant Useful Information for Chromosome 17q12 Microduplication Syndrome:

The following DoveMed website link is a useful resource for additional information:

http://www.dovemed.com/diseases-conditions/rare-disorders/