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What is Down Syndrome?Down syndrome, also called DS, is a condition caused by a mutation in the chromosomes during cell division. This mutation is a random event – it is not caused by environmental factors or by anything the parents did. In most people with Down syndrome, this mutation results in an extra copy of Chromosome 21. The extra genetic material disrupts the normal course of development of the body and the brain. Down syndrome is the most frequent genetic cause of mild to moderate developmental delay. How Common is Down Syndrome?Down syndrome occurs in about 1 in every 800 births, affecting people in all races and economic group.
Who is at Risk for Down Syndrome?The chance of having a baby with Down syndrome increases as a woman gets older—from about 1 in 1,250 for a woman who gets pregnant at age 25, to about 1 in 100 for a woman who gets pregnant at age 40. But, because younger women have more babies, most babies with Down syndrome are born to women under age 35. Parents who have already have a baby with Down syndrome or who have abnormalities in their own chromosome 21 are also at higher risk for having a baby with Down Syndrome.
What is Chromosome 21?Humans normally have 46 chromosomes in each cell, divided into 23 pairs. Chromosome 21, the smallest of these pairs, likely contains about 300 to 400 genes – only 1.5 percent of a person's DNA. Chromosome 21 abnormalities can cause intellectual disability, delayed development, characteristic facial features, and other problems.
What Are The Types of Down Syndrome?Trisomy 21This is the most common form of Down syndrome, accounting for about 95% of all cases. A person with Trisomy 21 has three copies of chromosome 21 (instead of the usual two copies) in every cell of his or her body.
Mosaic Down SyndromeThis form of Down syndrome results when a person has an extra copy of chromosome 21 in only a portion of their body's cells. It occurs during cell division in one of two ways. In the first scenario, the original fertilized cell has three copies of chromosome 21, but as it begins to divide, a copy of the cell manages to repair itself. That results in a mixture of mutated cells dividing alongside normal cells to create the baby. In the second scenario, the original cell is a healthy cell, but as it begins to divide, the mutation occurs. Again, this results in a mixture of mutated cells dividing alongside healthy cells to create the baby. Although people with Mosaic Down syndrome do have healthy cells, the end result is basically the same – Down syndrome. They don't have a physical or mental advantage or disadvantage compared to other Down syndrome babies.
Translocation Down SyndromeThis form of Down syndrome occurs when part of chromosome 21 becomes attached (translocated) to another chromosome during the formation of egg and sperm cells, or very early in fetal development. Affected people have two copies of chromosome 21, plus extra material from chromosome 21 attached to another chromosome.
Is Down Syndrome Inherited?In almost all cases, Down syndrome is the result of a random mutation - not something that is inherited from the patients. However, Translocation Down syndrome can be inherited.
What Are The Characteristics of Down Syndrome?Note: This section was created by the author of the phenomenal blog Down Syndrome New Mama. It is used here with her permission.
Just as newborn babies of differing nationalities or races have visible distinguishing features, so do babies with Down syndrome. While babies with Down syndrome do share some unique features, they mostly look like their biological parents and other family members. All babies are different and not every baby will have all or even most of the physical characteristics described below. Head: Your baby may have a marginally smaller head circumference. This size difference is hardly noticeable and you may not even see it or realize it until your pediatrician measures him and marks his growth chart. The back of your baby’s neck may be chunky but this disappears with age. The back of your baby’s head may be a bit less rounded than the average newborn. Face: Babies with Down syndrome have very delicate facial features (which have no negative effect on your baby’s senses or intelligence.) You will find that your baby’s features are very proportionate. Nose: Your baby may have a cute button nose with a softly contoured nasal bridge. This smoothness lends itself to a slightly more broad facial appearance. Eyes: Your baby’s eyes may turn gently upward at the outer edge. His actual eyes will be the same size as any other baby but may give the illusion of being beautifully enhanced if your baby has sparkling brushfield spots. Your baby’s eyes may also have small crinkles at the inner corner called epicanthal folds. Mouth: Your baby may have a little rosebud mouth. A smaller mouth may give the illusion that an average sized tongue is bigger than it actually is, (though the jury is still out on whether some children with Ds do have more ample tongues.) Ears: Babies with Ds are graced with petite ears that may or may not have a slight curve at the top. Sometimes baby’s ears are set a little further down on his head though this is hardly noticeable. Hands: Some babies with Ds have a single line on their palms called a transverse palmar crease. This crease occurs in more than 3 percent of the general population.Your baby’s hands may be smaller and his fingers maybe shorter than average. This does not interfere with a baby’s gross or fine motor skills. Feet: some babies have a small space between their first and second toes which is often accompanied by a vertical crease on the sole at this spot. Chest: Your baby’s chest may appear slightly bowed out or slightly depressed. This minor difference in shape has no negative effect on your baby. Skin and hair: You may find yourself with a fair-skinned baby who has lighter colored hair than yours. Some babies have very fine soft hair that may be thin in spots. These thinner spots should fill in as your baby grows. Muscle tone: Many babies with Ds have low muscle tone. While this has no bearing on how your baby looks, you will notice that your baby is a bit floppy with an amazing level of flexibility. What Other Health Problems Are Associated With Down Syndrome?People who have Down syndrome have an elevated risk for a variety of other medical problems:
- Congenital heart disease
- Early onset pulmonary hypertension
- Hearing loss
- Cataracts and other vision disorders
- Intestinal problems, such as a blocked small bowel or esophagus
- Celiac disease (a digestive disease that interferes with food absorption)
- Hypothyroidism (which causes a slow metabolism)
- Skeletal problems (shortened femurs, hyperflexibilty of joints, and many other problems)
- Transient myelodysplasia (defective development of the spinal cord)
- Leukemia
- Seizure disorders
- Dementia
How is a Baby Tested for Down Syndrome?Prenatal ScreeningA screening test can determine if an unborn baby has an increased likelihood for Down syndrome. Because the chances of having a baby with Down syndrome increase with the age of the mother, many health care providers recommend that women over age 35 have prenatal testing for the condition. Testing the baby before it is born to see if he or she is likely to have Down syndrome allows parents and families to prepare for the baby’s special needs. The simplest test, which is non-invasive, checks the levels of three markers in a drop of the mother's blood. If the markers show an increased likelihood of Down syndrome, additional diagnostic testing can be performed. Options for additional prenatal screening include:
Amniocentesis: This test is an analysis of a small sample of fetal cells from the amniotic fluid in the womb. The sample is taken through a needle, guided by ultrasonic imaging, inserted through the mother's belly. This test cannot be performed until the 14th to 18th week of pregnancy, and it usually takes additional time to determine whether the cells contain extra material from chromosome 21. The risk of a miscarriage caused by amniocentesis is low.
Chorionic Villus Sampling (CVS): This test is an analysis of a small tissue sample of chorionic villi - tiny, finger-shaped growths found in the placenta. The genetic material in chorionic villus cells is the same as the genetic material of the baby's own cells. The tissue sample is taken with a thin catheter inserted into the mother's vagina and guided by ultrasonic imaging through the cervix and into the placenta. The sample can also be collected through a long, thin needle inserted through the belly. This test is conducted at 9 to 11 weeks of pregnancy, and carries a 1-2% risk of miscarriage.
Percutaneous Umbilical Blood Sampling (PUBS): This test – an analysis of blood from the fetus – is the most accurate screening method. The blood sample is taken through a needle, guided by fluoroscopic imaging, inserted through the mother's belly and into the baby's umbilical cord. Results are usually available within three days. This test cannot be performed until the 18th to 22nd weeks, and it carries the greatest risk of miscarriage.
After the BirthOnce the baby is born, a genetic test called a chromosome analysis is performed on a sample of the baby's blood or skin cells to confirm the presence of an extra chromosome 21.
How Commonly Are Down Syndrome Babies Aborted?In the U.S., more than 90 percent of all babies with Down syndrome are aborted. This is a subject of intense debate within the Down syndrome community.
Is There a Cure for Down Syndrome?No - there is no cure for Down syndrome. The extra chromosome 21 is present in cells throughout the body, and this genetic information cannot be removed or deactivated.
What Medical Issues May I Encounter When Caring for a Newborn With Down Syndrome?Breast Feeding DifficultyBabies with Down syndrome often have hypotonia, or poor muscle tone. Because they have a reduced muscle tone and a protruding tongue, feeding babies with Down syndrome usually takes longer. Mothers breast-feeding infants with Down syndrome should seek advice from an expert on breast feeding to make sure the baby is getting sufficient nutrition. Hypotonia may also affect the muscles of the digestive system, in which case constipation may be a problem.
Heart ProblemsBecause about 40 to 60 percent of babies born with Down syndrome have a heart defect, all newborns with Down syndrome have their heart checked with an electrocardiogram and an echocardiogram. If a heart defect is detected, the infant is referred to a pediatric cardiologist for medical management or to a pediatric cardiac surgeon for early surgical repair.
Digestive ProblemsSome infants with Down syndrome have difficulties with swallowing or they may have blockages in their bowels. Surgery can be performed to correct these problems. Once corrected, they usually cause no further health issues.
What Additional Care Does An Infant/Preschooler With Down Syndrome Need?An array of specialized programs and related resources are available to help children with Down syndrome. Early referral, beginning at birth, to an early intervention program will help enhance development. All areas of development – including motor skills, language, intellectual abilities, and social and adaptive skills – should be followed closely.
Medical CareMedical care for infants with Down syndrome should include the same well-baby care that other children receive during the first years of life, as well as special attention to some problems that are more common in children with Down syndrome. For example, because low thyroid levels are more common in infants who have Down syndrome, children with Down syndrome need regular thyroid testing. And because they have an elevated risk for cataracts and other vision problems, children with Down syndrome should also have regular vision exams. Young children with Down syndrome may have frequent colds and sinus and ear infections - these should be treated early and aggressively to prevent hearing loss and chronic infections.
Physical/Speech DevelopmentChildren with Down syndrome are often developmentally delayed. A combination of low muscle tone (muscle weakness) and highly flexible joints can make rolling over, crawling, sitting and standing difficult. A physical or occupational therapist can tailor exercises to help strengthen the baby's muscles and encourage development. Because development of speech and language abilities may be difficult and may take longer than expected, speech therapy may be helpful.
Cognitive DevelopmentIt is not possible to determine the intelligence level of a baby with Down syndrome, and intelligence levels can vary greatly among individuals. Parents should keep in mind that children with Down syndrome have a wide range of abilities and talents, and each child develops at his or her own particular pace. It may take children with Down syndrome longer than other children to reach developmental milestones, but many of these milestones will eventually be met. Parents should make a concerted effort not to compare the developmental progress of a child with Down syndrome to the progress of other siblings or even to other children with Down syndrome. Early intervention can help many people with Down syndrome live productive lives well into adulthood.
What Are Some Issues That Affect Adolescents and Adults with Down Syndrome?Sexuality/FertilityLike all teenagers, individuals with Down syndrome undergo hormonal changes during adolescence. Therefore, teenagers with Down syndrome should be educated about their sexual drives. Males with Down syndrome generally have a reduced sperm count and rarely father children. Females with Down syndrome have regular menstrual periods and are capable of becoming pregnant and carrying a baby to term, however, they typically have significantly reduced rates of fertility.
Life Expectancy/Quality of LifePeople with Down syndrome are living fuller, richer lives than ever before as family members and contributors to their community. Many people with Down syndrome form meaningful relationships and eventually marry. Many adults with Down syndrome develop the skills they need to hold jobs and to live semi-independently. The life expectancy for people with Down syndrome has also increased substantially. In 1929, the average life span of a person with Down syndrome was nine years. Today, it is common for a person with Down syndrome to live to age fifty and beyond.
Aging and DementiaPremature aging is a characteristic of adults with Down syndrome. In addition, many people with Down syndrome experience dementia (memory loss and impaired judgment similar to that occurring in Alzheimer disease patients). This condition often occurs when the person is younger than forty years old. Family members and caretakers of an adult with Down syndrome must be prepared to intervene if the individual begins to lose the skills required for independent living.
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