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

• Xq Duplication Syndrome
• Partial Trisomy Xq Syndrome
• Trisomy Xq Syndrome

What is Chromosome Xq Duplication Syndrome? (Definition/Background Information)

• Chromosome Xq Duplication Syndrome is a rare chromosomal disorder caused by the presence of an extra copy of a small piece of chromosome X (on the long arm q) in the cells of the body leading to a set of associated signs and symptoms. These may be mild or severe, depending on several factors such as the amount of genetic material gained (duplicated), the number of genes affected, and the function of the affected genes
• Chromosome Xq Duplication Syndrome are typically inherited in an X-linked manner. The condition affects newborn children (congenital manifestation). Xq Duplication Syndrome generally affects males more severely than females. It can result in poor muscle tone, feeding difficulties, speech and language delays, abnormal facial features, 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 the use of learning and communication aids, physiotherapy, and surgery for correction of physical defects
• The prognosis is primarily dependent on the severity of the disorder, and it varies from one child to another. Many children with Chromosome Xq Duplication Syndrome are able to cope well through adequate treatment and supportive care. Some of the signs and symptoms associated with the condition are known to improve with time

Who gets Chromosome Xq Duplication Syndrome? (Age and Sex Distribution)

• Chromosome Xq Duplication Syndrome is a rare congenital disorder. The presentation of symptoms may occur at or following the birth of the child
• The condition predominantly affects males, although some females may be affected as well
• Worldwide, individuals of all racial and ethnic groups may be affected

What are the Risk Factors for Chromosome Xq Duplication Syndrome? (Predisposing Factors)

In some individuals, there are no identified risk factors for Chromosome Xq Duplication Syndrome.

• In many individuals, a positive family history is an important risk factor for Xq Duplication Syndrome
• 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 Xq Duplication Syndrome? (Etiology)

• Chromosome Xq Duplication Syndrome is caused by an extra copy of genetic material on the long arm (q) of chromosome X
  • In some cases, the condition occurs sporadically during embryonic development (termed de novo duplication)
  • In many cases, the chromosomal abnormality is inherited in an X-linked manner. In such cases, it is mostly a maternal inheritance (from the mother) 
• Males have one X and Y chromosome each (XY); thus, a duplication on the X chromosome causes associated signs and symptoms that may be significant. In females with two X chromosomes (XX), the manifestation of signs and symptoms is generally mild to absent
• Even though many genes in the Xq region may be affected, the involvement of the following three genes have been well characterized in the medical literature:
  • MECP2 gene
  • PLP1 gene
  • OPHN1 gene

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 Xq Duplication Syndrome?

The signs and symptoms of Chromosome Xq Duplication Syndrome vary significantly depending on the size of the duplication, the gender of the individual (whether male or female), and the genes found on the duplicated segment of the chromosome. In general, males with Chromosome Xq Duplication Syndrome are generally more severely affected than females with the duplication.

The associated signs and symptoms depend on what material is duplicated, how much duplication has occurred (quantity), where the duplications occurs (such as at the tip or center of the chromosome), and if the involvement of another chromosome is noted (known to occur in some cases).

The common signs and symptoms of Xq Duplication Syndrome typically observed in males include:

•  Short stature
• Low muscle tone (hypotonia)
• Feeding difficulties
• Developmental delay
• Intellectual disability
• Speech, language, and communication difficulties
• Small head size and other facial abnormalities
• Minor genetic anomalies
• Seizures
• Behavioral issues

In girls and women, the signs and symptoms are often mild and only short stature is prominently observed.

How is Chromosome Xq Duplication 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 Chromosome Xq Duplication Syndrome in the differential diagnosis. Often, specialized tests are necessary to confirm the disorder.

Chromosome Xq Duplication 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 vision assessment through various tests
• 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
• 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 Xq Duplication Syndrome?

The complications of Chromosome Xq Duplication Syndrome may include:

• Severe emotional stress for parents and caregivers
• Failure to thrive
• Severe intellectual deficiency
• Endocrine system dysfunction
• Brain abnormalities
• Inability to talk
• Difficulties with movement
• Frequent infections
• Abnormalities in bladder function
• Risk of falls and injury due to seizures
• Infertility
• Inability to live independently
• Reduced quality of life

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

How is Chromosome Xq Duplication Syndrome Treated?

There is no cure for Chromosome Xq Duplication 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 Xq Duplication Syndrome may involve:

• Seizure control using anticonvulsant medication, vitamin supplements, and ketogenic diet Employing learning strategies via music therapy, visual and tactile books, touch screen computers, etc.
• Speech and language therapy; the use of sign language may be beneficial
• Physiotherapy for weakened muscles, including incorporating daily exercise regimen
• Development of motor skills via daily exercises, swimming, and other adapted activities; use of specially-designed toys and daily-used items (such as spoons and cups)
• Use of walking aids including foot orthotics and special footwear
• For feeding difficulties, use of feeding tubes (temporary), medications, feed thickeners, including special diets and nutritional supplements
• Parenteral nutrition and specialized diets to address poor growth and malnutrition in children
• Hormone replacement therapy for endocrine gland abnormalities, if needed
• Surgical correction of physical defects, as assessed by a healthcare expert
• Antibiotic therapy for infections including prophylactic treatment
• Psychotherapy, behavior modification, and establishing discipline techniques, as necessary
• Occupational therapy

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

How can Chromosome Xq Duplication Syndrome be Prevented?

Chromosome Xq Duplication 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) 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 Xq Duplication 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 Xq Duplication Syndrome? (Outcomes/Resolutions)

The prognosis of Chromosome Xq Duplication 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, but it is generally difficult to predict the long-term outlook.

• Females are only mildly affected, while males are more severely affected and have typically poorer prognoses. Some of the abnormalities are known to resolve or improve with time
• Children with mild conditions (usually from small duplications) are generally able to cope well via appropriate treatment and adaptive behaviors as they get older

Additional and Relevant Useful Information for Chromosome Xq Duplication Syndrome:

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

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