DOWN SYNDROME
WHAT IS DOWN SYNDROME?
THE MOST COMMON GENETIC DISORDER.
Down syndrome is a genetic disorder that causes lifelong developmental delays and other problems. Down syndrome varies in severity, so developmental problems range from moderate to serious.
Down syndrome is the most common genetic cause of learning disabilities in children.
Increased understanding of Down syndrome and early interventions make a big difference in the lives of both children and adults with Down syndrome.
Down syndrome results when one of three types of abnormal cell division involving chromosome 21 occurs. All three cell division abnormalities result in extra genetic material from chromosome 21, which is responsible for the characteristic features and developmental problems of Down syndrome. The three genetic variations that can cause Down syndrome include:
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Trisomy 21.More than 90 percent of the time, Down syndrome is caused by trisomy 21. A child with trisomy 21 has three copies of chromosome 21 — instead of the usual two copies — in all of his or her cells. This form of Down syndrome is caused by abnormal cell division during the development of the sperm cell or the egg cell.
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Mosaic Down syndrome.In this rare form of Down syndrome, children have some cells with an extra copy of chromosome 21. This mosaic of normal and abnormal cells is caused by abnormal cell division after fertilization.
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Translocation Down syndrome. Down syndrome can also occur when part of chromosome 21 becomes attached (translocated) onto another chromosome, before or at conception. Children with translocation Down syndrome have the usual two copies of chromosome 21, but they also have additional material from chromosome 21 attached to the translocated chromosome. This form of Down syndrome is uncommon.
There are no known behavioral or environmental factors that cause Down syndrome.
Translocation Down Syndrome
Translocation Down syndrome occurs when two chromosomes, one of which must be a #21, join together at their ends. Instead of having three independent, separate number 21 chromosomes, a person with translocation Down syndrome has two independent #21 chromosomes and a #21 chromosome that is attached to another chromosome. The attached chromosomes are called a derivative chromosome and can occur for the first time in the person with translocation Down syndrome (de novo translocation), or the derivative chromosome can be inherited from a parent.
When a child is diagnosed with translocation Down syndrome, it is very important that the parents of the child also have karyotype testing to see if they carry this translocation.
While translocation Down syndrome occurs via a different mechanism, a child with translocation Down syndrome will have the same features and symptoms as a child with trisomy 21.
Translocation Down syndrome is one of the three forms of Down syndrome (the others are trisomy and moasicism). It accounts for 4 to 5% of Down syndrome cases.
Pronunciation: Trans low kay shun Down syndrome
Examples:
The karyotype test revealed that the infant had translocation Down syndrome due to a 14:21 chromosome translocation inherited from his father.
New Down syndrome patient registry will facilitate contacts and information sharing among families, patients, researchers and parent groups. The National Institutes of Health has awarded a contract to PatientCrossroads to operate the registry. The company has created patient-centric registries for muscular dystrophy and many rare disorders.
People with Down syndrome or their family members will be able to enter contact information and health history in an online, secure, confidential database. Registry participants will be able to customize their profile, update it online, and choose which information they would like to display, including reminders about their own medical care and general information about Down syndrome. They also will be able to compare their own medical information to that of other registrants in a confidential and anonymous manner.
If a participant gives permission to be contacted, clinicians and researchers who are authorized to access the database will be able to contact these individuals to see if they are interested in participating in a research study.
Ultimately, the registry will be able to link to biorepositories of tissue samples and other resources, with the goal of making it easier for patients to take part in clinical studies for new medications and other treatments for Down syndrome.
The contract, which will support the creation of the registry through September 2013, received $300,000 in funding for its first year.
“The new registry provides an important resource to individuals with Down syndrome and their families,” said Yvonne T. Maddox, deputy director of the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), which is funding the registry. “The registry links those seeking volunteers for their research studies with those who most stand to benefit from the research.”
Down syndrome most frequently results from an extra copy of chromosome 21 in the body’s cells. Infants with Down syndrome are likely to have certain physical characteristics, such as short stature and distinctive facial features, as well as health conditions like hearing loss, heart malformations, digestive problems, and vision disorders. Although Down syndrome most commonly results in mild to moderate intellectual disability, the condition occasionally involves severe intellectual disability. In addition, some individuals with Down syndrome age prematurely and may experience dementia, memory loss, or impaired judgment similar to that experienced by individuals with Alzheimer disease.
“Down syndrome is complex,” Dr. Maddox said. “A wide array of scientific expertise is required to address all its aspects in a comprehensive manner.”
Development of a patient registry was a leading recommendation in the 2007 NIH Down Syndrome Research Plan, which sets goals and objectives for the Down syndrome research field. Together with the Global Down Syndrome Foundation, the NICHD sponsored the Down syndrome National Conference on Patient Registries, Research Databases, and Biobanks to solicit the advice of a number of experts from the advocacy community, federal agencies, industry, and the clinical and research communities on how best to establish a Down syndrome registry.
The plan for the registry was supported by the public-private Down Syndrome Registry, which was established by the NIH in 2011 to foster the exchange of information on Down syndrome research, and to implement and update the Research Plan. Membership on the Registry includes individuals with Down syndrome and family members, representatives from prominent Down syndrome and pediatric organizations, and members of the NIH Down Syndrome Working group, an internal NIH group that coordinates NIH-supported Down syndrome research,
“We’re grateful to those who provided us with the advice that allowed us to establish a national registry,” Dr. Maddox said. “We are happy that this important step in furthering research on Down syndrome has been accomplished and hope that many families will take advantage of the opportunity to sign up as soon as the registry goes online.”
MOSAIC DOWN SYNDROME
Mosaic comes from the Greek word mouseios which means of the muses, artistic.
When somebody talks about trisomy, or partial trisomy they mean that as far as anyone can tell the chromosomal anomaly occurs in every cell of the body.With mosaicism there is a chromosomal anomaly, but not in every cell. Some cells have the "normal" complement and arrangement of chromosomes and some cells have the chromosomal anomaly.
The effect of mosaicism is wide and variable. Effected individuals can have all of the problems associated with the "full" variant of the chromosomal anomaly or none and anywhere in between.
Some people also feel that if an individual has a mosaic chromosomal anomaly that they do not have the physical problems and or cognitive problems of those who have a "full" version of the chromosomal anomaly. Sadly this is not the case.
Children with a mosaic diagnosis have just as much risk of early death as those with a "full" diagnosis. It is not the chromosomal anomaly itself which causes the early death of our children but how the changes in the genetic material effects the developing baby. Children with a mosaic diagnosis are just as likely to have life threatening cardiac problems, apneas, feeding problems and other potentially life threatening or life shortening congenital problems.
Parenting a child with Down syndrome has its challenges. Don't let others' beliefs in faulty information add to them for you.
Here are some common misconceptions about Down syndrome and the facts you need to set people straight on the realities.
MYTH: Down Syndrome is a rare disorder.
FACT: Down syndrome is not rare. About 1 in every 700 babies is born with Down syndrome and over 6000 babies are born with Down syndrome in the US each year. Currently, it is estimated that there are over 350,000 individuals with Down syndrome in the United States.
MYTH: Most children with Down syndrome are born to older parents.
FACT: Over 80% of babies with Down syndrome are born to women under the age of 35, and the average age of a mother of an infant with Down syndrome is 28 years.
MYTH: Down syndrome is not treatable.
FACT: While there is no cure for Down syndrome, there are many treatments available for the problems associated with Down syndrome.
MYTH: People with Down syndrome have severe mental retardation.
FACT: Most people with Down syndrome have only mild to moderate mental retardation. Individuals with Down syndrome have IQ scores of 30 to 60, but much variation exists. More important than IQ scores is the fact that all individuals with Down syndrome are capable of learning.
MYTH: Children with Down syndrome must be placed in separate special education programs.
FACT: Most children with Down syndrome in the United States are “mainstreamed” into regular schools. They attend regular classes for some subjects and attend special classes for other subjects. Each school system is required to provide the best learning environment possible for all special needs children.
MYTH: People with Down Syndrome will live at home forever.
FACT: A large percentage of adults with Down syndrome live semi-independently in assisted living facilities and group homes. Adults with Down syndrome often hold jobs and have romantic relationships.
MYTH: People with Down syndrome are always happy.
FACT: People with Down syndrome experience a full range of emotions such as sadness, anger and happiness, just like everyone else.
MYTH: Individuals with Down syndrome die young.
FACT: The average life expectancy of an individual with Down syndrome is now 60 years of age.
