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What is Dup15q Syndrome?
What is Dup15q Syndrome?
How often do duplications of chromosome 15 occur?
What problems are caused by duplications of chromosome 15?
Prognosis
At the present time, there is no specific treatment that can undo the genetic pattern seen in people with idic15 or int dup15. Although the fundamental genetic differences cannot be reversed, children and adults have been known to benefit from some of the following:
Dup15q Syndrome and Seizures
Dup15q Syndrome and Autism
Chromosome 15q11.2-13.1 duplication syndrome (commonly known as dup15q or dup15q syndrome)
is a clinically identifiable syndrome which results from duplications
of chromosome 15q11.2-13.1. These duplications most commonly occur in
one of two forms. These include an extra isodicentric 15 chromosome,
abbreviated idic(15), or an interstitial duplication 15, abbreviated int
dup(15). When the extra genetic material comes from the paternal
chromosome a child may have normal development. However, when the
duplicated material comes from the maternal chromosome, developmental
problems are often the result. In most cases of chromosome 15q11.2-13.1
duplication syndrome, the chromosome duplication is not inherited, but
occurred as a random event during the formation of reproductive cells
(eggs and sperm).
How often do duplications of chromosome 15 occur?
Researchers think that approximately 1 in 8,000 babies are born with an extra chromosome that came from chromosome 15. The most common type of marker chromosome 15 is very small and does not cause any problems. We don’t know the frequency of the larger ones, that cause the symptoms seen in dup15q and int dup15 but one researcher estimates they occur in about 1 in 15,000 – 20,000 births.
Generally, people with idic15 do not have family members with the chromosome abnormality. The idic15 usually forms by chance in one person in the family. Children with idic15 are born to parents of every socioeconomic, racial, and ethnic background. There is no known link between idic15 and environmental or lifestyle factors. In other words, there is nothing that parents did before or during pregnancy to cause their child to be born with idic15.
Generally, people with idic15 do not have family members with the chromosome abnormality. The idic15 usually forms by chance in one person in the family. Children with idic15 are born to parents of every socioeconomic, racial, and ethnic background. There is no known link between idic15 and environmental or lifestyle factors. In other words, there is nothing that parents did before or during pregnancy to cause their child to be born with idic15.
What problems are caused by duplications of chromosome 15?
Since chromosomes carry genes that determine how our bodies grow and develop, having extra chromosomal material can alter a person’s physical and mental development. Unlike many other chromosomal syndromes, there are few characteristic physical findings associated with idic15 and int dup15. There is also a wide range of severity, so that two children with the same chromosome pattern may be very different in terms of their abilities. In general, the following features are found in most people with idic15 and int dup15 to varying degrees:
- Poor Muscle Tone (hypotonia) particularly in babies, with delayed milestones (although the vast majority will walk independently),
- Cognitive Disabilities/Learning Disabilities
- Gross and fine motor Delays
- Autism Spectrum Disorders
- Seizure Disorders
- Speech/Language Delays
- Sensory Processing Disorders
- Attention Deficit Disorders (ADD/ADHD)
- Anxiety Disorders
- Behaviour challenges
- Other medical problems include recurrent respiratory infections in childhood, middle ear effusions requiring tubes, eczema, precocious puberty, other menstrual irregularities, overeating and weight gain. Scoliosis is also reported in adolescence
- Small size for age
- Minor unusual physical features, including wide-spaced eyes with skin folds at the inner corners (epicanthal folds); noticeable unfolding of the edge of the ears; short, upturned nose with a low or flattened nasal bridge; and full lips
- As with any chromosomal syndrome there can be differences in the way their hearts, kidneys, or other body organs are formed. Parents should check with their genetics specialist for specific recommendations regarding medial evaluations.
Prognosis
At the present time, there is no specific treatment that can undo the genetic pattern seen in people with idic15 or int dup15. Although the fundamental genetic differences cannot be reversed, children and adults have been known to benefit from some of the following:
- Early Intervention (speech, physical, occupational, and sensory integration therapies)
- Ongoing Special Education
- Total Communication Systems (a combination of speech, sign, gestures and picture exchange)
- Behavioral Strategies
- Sensory Integration Strategies
- Medical Management of Symptoms
Dup15q Syndrome and Seizures
Seizures represent an important medical feature of idic15 syndrome. Over half of people with idic15 will have at least one seizure. The vast majority of those will experience their first seizure before age 5, but seizure onset occurs through puberty and young adulthood in this population (**Devin's first seizure occurred at 7 years old and is currently controlled with medication**. There are many types of seizures experienced by individuals with dup15q. Affected individuals can start with one seizure type and other seizure types may emerge as the individual ages. Response to treatment is variable as some seizures are easily controlled with the first medication, while others are controlled for a while then become more complex. Some individuals experience intractable seizures that have never been controlled by medication.
Dup15q Syndrome and Autism
For more than 12 years, scientists have noticed that some individuals with autism also have dup15q. In fact, idic(15) is the most frequently identified chromosome problem in individuals with autism. (A chromosome anomaly involves extra or missing chromosomal material, not changes within the genes such as Fragile X syndrome). It is suggested that the co-occurrence of autism and idic(15) is not by chance. There may be a gene or genes in the 15q11.2-q13.1 region that is/are related to the development of autism in some individuals.
Genetic research studies of individuals without chromosome anomalies also support this idea that an autism-related gene may be present in 15q11.2-q13.1. Specifically, research studies found that certain DNA markers from the 15q11.2-q13.1 region were found more often in individuals with autism than in individuals without autism. Although these DNA markers are too small to be genes, they suggest that researchers may be getting close to finding an autism gene in this region.
A recent study reported the introduction of two extra copies of just a single gene present in the 15q11.2-13.1 region, Ube3a, into mice to model the gene copy number expressed in the brain in idic(15). These mice displayed autism-related behavioral deficits including impaired social interaction, reduced ultrasonic vocal communication, and increased repetitive behavior (self-grooming).
Please visit www.dup15q.org for additional information on dup15q Syndrome.