The most common form of Down syndrome is known as Trisomy 21. Individuals with Trisomy 21 have 47 chromosomes instead of the usual 46 in each of their cells. The most common form of Down syndrome is known as Trisomy 21. Individuals with Trisomy 21 have 47 chromosomes instead of the usual 46 in each of their cells. The condition results from an error in cell division called non-disjunction. Prior to or at conception, a pair of 21st chromosomes in either the sperm or the egg fails to separate.

As the embryo develops, the extra chromosome is replicated in every cell of the body. This error in cell division is responsible for 95 percent of all cases of Down syndrome. Having an extra copy of this chromosome means that each gene may be producing more protein product than normal. Cells seem to tolerate this better than having not enough protein, or having altered protein due to a mutation in the DNA sequence. The condition leads to impairments in both cognitive ability and physical growth that range from mild to moderate developmental disabilities. Through a series of screenings and tests,

Down syndrome can be detected before and after a baby is born. The only factor known to affect the probability of having a baby with Down syndrome is maternal age. That is, less than one in 1,000 pregnancies for mothers less than 30 years of age results in a baby with Down syndrome. For mothers who are 44 years of age, about 1 in 35 pregnancies results in a baby with Down syndrome. Because younger women generally have more children, about 75% – 80% of children with Down syndrome are born to younger women.

How do people get Down syndrome?

Down syndrome occurs because of an abnormality characterized by an extra copy of genetic material on all or part of the 21st chromosome. Every cell in the body contains genes that are grouped along chromosomes in the cell’s nucleus or center. There are normally 46 chromosomes in each cell, 23 inherited from your mother and 23 from your father. When some or all of a person’s cells have an extra full or partial copy of chromosome 21, the result is Down syndrome.

There are normally 46 chromosomes in each cell, 23 inherited from your mother and 23 from your father.Down syndrome is typically caused by what is called non-disjunction. If a pair of number 21 chromosomes fails to separate during the formation of an egg (or sperm), this is referred to as non-disjunction. When that egg unites with a normal sperm to form an embryo, that embryo ends up with three copies of chromosome 21 instead of the normal two. The extra chromosome is then copied in every cell of the baby’s body. Non-disjunction events seem to occur more frequently in older women. This may explain why the risk of having a baby with Down syndrome is greater among mothers age 35 and older.

What are the symptoms of Down syndrome?

Symptoms is really a misnomer. People have Down syndrome and their characteristics. Despite the variability in Down syndrome, individuals with Down syndrome have a widely recognized characteristic appearance. Typical facial features include a flattened nose, small mouth, protruding tongue, small ears, and upward slanting eyes. The inner corner of the eyes may have a rounded fold of skin (epicanthal fold). The hands are short and broad with short fingers, and may have a single palmar crease.

White spots on the colored part of the eye called Brushfield spots may be present. Babies with Down syndrome often have decreased muscle tone at birth. Normal growth and development is usually delayed and often individuals with Down syndrome don’t reach the average height or developmental milestones of unaffected individual.

How is Down syndrome treated?

No cure exists for Down syndrome. But physical therapy and/or speech therapy can help people with the disorder develop more normally. Screening for common medical problems associated with the disorder, followed by corrective surgery, can often improve quality of life. Moreover, enriched environments significantly increase their capacity to learn and lead a meaningful life.

Interesting facts about Down syndrome

• Down syndrome is really the only trisomy compatible with life. Only two other trisomies have been observed in babies born alive (trisomies 13 and 18), but babies born with these trisomies have only a 5% chance of surviving longer than one year.
• In 90% of Trisomy 21 cases, the additional chromosome comes from the mother’s egg rather than the father’s sperm.
• Down syndrome is the most common genetic disorder caused by a chromosomal abnormality. It affects 1 out of every 800 to 1,000 babies.
• Down syndrome was originally described in 1866 by John Langdon Down. It wasn’t until 1959 that a French doctor, named Jerome Lejeune, discovered it was caused by the inheritance of an extra chromosome

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All cells in the human body comprise of 23 pairs of chromosome. Amongst these pairs of chromosomes, one chromosome from each set is derived from one’s father and the other from the mother. Down syndrome is associated with chromosome 21. Random errors in cell division result in the partial or complete presence of three chromosomes 21 instead of a normal pair. The physical and cognitive disabilities arising due to the condition are the consequence of excessive genetic material provided by the extra chromosome 21.

There are three variations of Down syndrome. The most common form of Down syndrome is referred to as Trisomy 21. Owing to errors in cell division, either of the reproductive cells, that is the sperm or the egg ends up with an extra copy of chromosome 21.

Rarely, a form of Down syndrome called “Mosaic” Down syndrome may occur when an error in cell division occurs after fertilization (1 to 2 percent of cases). These persons have some cells with an extra chromosome 21 and others with the normal number.When this abnormality occurs after fertilization, the fetus may be born with Mosaic Down syndrome.

The third variation of the disease is known as Translocation Down syndrome. In this form of the disorder, a segment of chromosome 21 gets attached to another chromosome, usually chromosome 14 either prior to or during conception. Those suffering from this disorder possess only a pair of chromosomes 21, but have some extra genetic material of the same chromosome attached with the chromosome which is the site of the translocation.

Translocation Down syndrome is the only variant of the disease that can be inherited by the offspring. Other than these three causes, the disease is not known to be caused due to any behavioral or environmental factors.

In every cell in the human body there is a nucleus, where genetic material is stored in genes. Genes carry the codes responsible for all of our inherited traits and are grouped the objects called chromosomes.

In 1866 the physical characteristics of people with Down Syndrome were linked with decreased intellectual ability and grouped as one syndrome. The English physician, John Langdon Down, was the first to publish these findings.

Due to the fact that the facial features of people with Down Syndrome were similar to those of people from Mongolia, he used the term mongoloid to refer to a person with (what is now known as) Down Syndrome.

It was not until 1959 that Dr. Jerome Lejeune, a French physician, made the discovery that Down Syndrome was the result of a chromosomal abnormality. His research led him to the fact that the cells of people with Down Syndrome (mongoloids, at the time) had 47 chromosomes, whereas the cells of people without the syndrome only had 46 chromosomes.

Just a little while after that, it was discovered that chromosome number 21 contained an extra partial or complete chromosome in these so called “mongoloids”. Thus, the term Trisomy 21 was born. Mongoloid is now considered to be a pejorative term and should be avoided when referencing a person with Down syndrome.

In the vast majority of cases, Down Syndrome is not hereditary – meaning it is no one’s fault if a baby has the condition

As yet we do not know what causes the presence of an extra chromosome 21. It can come from either the mother or the father, but most commonly from the mother. There is no way of predicting whether a parent is more likely to produce an egg or sperm with 24 chromosomes. There is a definite link with advanced maternal age for reasons yet unknown. However, most babies with Down syndrome are born to women under the age of 35, as younger women have higher fertility rates.

For every 800 babies born, one will have Down syndrome. Down syndrome affects people of all ages, races, religious backgrounds and economic situations. Nothing done before or during pregnancy can cause Down syndrome. It occurs in all races, social classes and in all countries throughout the world. It can happen to anyone.

The diagnosis of Down syndrome is usually made soon after the birth of the baby because of the baby’s appearance. There are many physical characteristics associated with the condition, which may lead a parent or midwife, or other medical professional, to suspect that the baby has Down syndrome. As pre-natal testing has become more prevalent, many women are now able to get tested during their first trimester

Some of the features include:

• Reduced muscle tone which results in hypotonia
• A flat facial profile, flat nasal bridge, small nose
• Eyes that slant upwards and outwards, often with a fold of skin that runs vertically between the lids at the inner corner of the eye (epicanthic fold)
• A small mouth which makes the tongue seem slightly large
• A big space between the first and second toe (sandal gap)
• Broad hands with short fingers and a little finger that curves inwards. The palm may have only one crease across it (single palmar crease)
• A below average birth weight and length at birth

It is not uncommon for these features to also occur in the general population. Therefore a chromosome test (karyotype) needs to be performed before a positive diagnosis could be made.

There are certain health problems that are more common in people with Down syndrome than in the rest of the population. These include:

• 40-50% of babies with Down syndrome are born with heart problems, many of which require heart surgery
• A significant number of people with Down syndrome will have hearing and sight problems
• Thyroid disorder
• Poor immune system
• Respiratory problems, coughs and colds
• Obstructed gastrointestinal tract

However, with advances and increased access to medical care most of these problems are treatable. None of these problems is unique to people with Down syndrome – they also occur in the rest of the population.

It is also important to remember that some people with Down syndrome do not experience any health problems. Advances in treatments and increased access to medical care have also meant that people with Down syndrome are living much longer. Life expectancy is now put at 60-65, and many people with Down syndrome live even longer.

All people with Down syndrome will have some degree of intellectual disability. Children with Down syndrome do learn to walk, talk and be toilet trained but in general will meet these developmental milestones later than their typical peers. There is a wide variation in ability in people with Down syndrome just as there is in the rest of the population. Early intervention programs help in all areas of child development are now widespread. These programs can include speech and physical therapy as well as home teaching programs for the child and the family.

If you have more questions or want to join a community of people that care for someone with Down syndrome, please join our social network.

Related articles

• What is the cause of the Down syndrome disorder (wiki.answers.com)

I get emails or phone calls very often from families who have a new diagnosis of T21. Sometimes it is their friends or relatives who make the first contact. Then soon, the parents are emailing or calling. This has brought me a unique perspective of the entire process of receiving the news of Trisomy 21, Down syndrome, in utero. I would love to share some of the things that are said to me, and clear up any confusion.

Myth #1:

My child will die young, as individuals with Down syndrome do not live longer than the mid 20′s

Reality: This is simply not true. Individuals are living well into their 50′s and even longer, now that proper medical care is being given to treat heart or other life threatening conditions. Many individuals are capable of employment, living independently, and enjoy many hobbies and activites. See our T21 individuals in the news.

Myth #2:

Your child will suffer.

Reality: Again, this could not be further from the truth. Many people in the world require corrective surgery. If your child needs surgery for any reason, the medical care given to individuals with Ds is wonderful. You can expect your child to do beautifully, and continue to thrive. While as many as 30-50% my have a heart condition, only approximately 5% will require open heart. The care of that 5%, by qualified pediatric cardiologists, is remarkable. The remaining 25-45% will have other less invasive procedures, or just be monitored. The cardiac care these days is absolutely amazing!! All other corrective surgery is also incredible. Any medical conditions can be treated today, unlike years ago when treatment was unknown. With proper medical care, individuals go on to live happy and wonderful lives!

Myth #3:

The physicians have told me that my child’s Down syndrome is worse than other cases.

Reality: This is simply impossible to tell in utero. Or even right at birth for that matter. Even children with many surgical needs have gone on to do amazing things. Karen Gaffney is an amazing example of an individual who needed much corrective surgery, and has gone on to do amazing things. She is not unique, this happens all over the world. I have met soo many families who have seen their family member through medical care, and the individual goes on to do beautifully in every way.

Myth #4:

The physicians have told me my child has a mild case of Down syndrome.

Reality: While there are many different abilities for individuals with Down syndrome, a physican can not tell in utero or at birth, how a child will fare. Most instances where an individual has a more difficult time learning or behaving, is indication of a dual diagnosis. Typical children have this exact possiblity. If a child needs corrective surgery, that does notmean they will have severe developmental delays. Individuals with Down syndrome benefit from loving homes, early intervention, inclusive education, appropriate medical care and positive public attitudes.

Myth #5:

Your chances of having a child with Down syndrome increases greatly after age 35.

Reality: Yes, indeed your chances increase. But let’s discuss the word greatly. When we see the estimated rates in the books, you may see that at age 20 it is 1/1231. At age 25 it is1/887. At age 30 it is 1/685. At age 35 it is 1/274. And finally at age 40 it is 1/78. So, yes, your chance does increase with age. And boy, when you put it that way, it sure does look like it increases greatly. However, if you were to look at these numbers in percentages, they look a little more interesting. Age 20: .08%. Age 30: .15%. Age 35: .36%. Age 40: 1%. So as one physician said to us, “Leave the guilt at the door”, because at age 39, our estimated risk was 1/100. That means there was a 1% chance of having a child with Down syndrome. That means we had a 99% chance of not having a child with Down syndrome. He went on to add, “Who would think to not have a child if you have a 99% chance of this not happening?” Now, to set the record straight, this was the way he put it. We say, ”Wow, what a miracle. We had a 99% chance of not having this gift from God. Whew, that was close!” We don’t ever want to imagine what our life would be like with our our beautiful daughter. So indeed, the numbers do increase. However, when you look at it from a percentage view point, it sure makes this drastic rise, that many professionals talk about, seem pretty insignificant doesn’t it? You have a better chance of having other things happen to you. In fact, there are a lot of ailments we all have a greater chance of having than the chance of being blessed with a child with Down syndrome. One additional point to add to this; 80% of all children born with Ds are born to mothers 35 and under. Many think this happens only to older mothers, since there is an increase. However, as you can see, the great increase is not as great as is told, so with the decrease in women having children at older ages, this makes the number of children with Down syndrome being born more often to younger moms. Numbers are interesting aren’t they?

Myth #6:

Bringing a child who has Down syndrome into your family will be harmful to your other children.

Reality: Again, just not true! In fact it is just the opposite. Your other children actually have a higher chance of becoming more compassionate and accepting of other people. The benefits have been a best kept secret until Dr. Brian Skotko did a study on the affects of having a sibling with Down syndrome. Another unexpected blessing. Read here for more information. Dr. Brian Skotko’s study.

Myth #7:

There is a higher divorce rate for families who have a child with Down syndrome.

Reality: While divorce can happen in any family, the studies are actually showing it is currently lower in the families who have a member who happens to have Trisomy 21. Perhaps it has something to do with the many lessons they teach us about life.Click here to see more on this.

Myth #8:

This will ruin your life.

Reality: Continue down this page to see how this has affected the families who have chosen to write about their experiences. I am sure you will see that this has done anything but ruin their lives. It has indeed been a new journey for all of our families, and one that can require many graces at times. (Show me parenting that doesn’t need more at some times!) But ruining our lives… that is simply not happening! An extra chromosome is all it is. The fear of that, is much more paralyzing than the reality. Enjoy your pregnancy! Enjoy your baby!

Age Related Risks

Generally, the chance of having a Down syndrome birth is related to the mother’s age. The odds of having a child with Down syndrome at age 35 are about 1 in 350. Under age 25, the odds are about 1 in 1,400. At age 40, the odds are about 1 in 100.

Types of Down Syndrome

There are three types of Down syndrome:

• Trisomy 21 — An estimated 95 percent of people with Down syndrome have Trisomy 21, meaning an individual has three instead of two number 21 chromosomes. We normally have 23 pairs of chromosomes, each made up of genes. During the formation of the egg or the sperm a woman’s or a man’s pair of chromosomes normally split so that only one chromosome is in each egg or sperm. In Trisomy 21, the 21st chromosome pair does not split and a double-dose goes to the egg or sperm. An estimated 95 percent to 97 percent of the extra chromosome is of maternal origin.
• Translocation — This occurs in about 3 percent to 4 percent of people with Down syndrome. In this type, an extra part of the 21st chromosome gets stuck onto another chromosome. In about half of these situations, one parent carries the extra 21st chromosome material in a “balanced” or hidden form.
• Mosaicism — In mosaicism, the person with Down syndrome has an extra 21st chromosome in only some of the cells but not all of them. The other cells have the usual pair of 21st chromosomes. About 1 percent to 2 percent of people with Down syndrome have this type.

In addition to developmental delays, some common physical traits are an upward slant of the eyes; flattened bridge of the nose; single, deep crease on the palm of the hand; and decreased muscle tone. A child with Down syndrome, however, may not have all these symptoms.

Typically, parents of Down syndrome babies don’t have any symptoms themselves even though they may carry an abnormal gene.

Risk of Recurrence

After the birth of a child with Down syndrome, the risk of having a second child with Down syndrome depends on what caused the condition in the first child. A medical geneticist or genetic counselor should be consulted to get more precise information on the risks. The following are some general guidelines:

• Trisomy 21 — The risk of Down syndrome recurring is either 1 percent to 2 percent or the risk based on the mother’s age, whichever is higher.
• Translocation — The risk of Down syndrome recurring depends on if the translocation was inherited or not inherited. If not inherited, the risk is the same as the risk based on the mother’s age. If inherited, the risk depends on the type of translocation and the sex of the parent carrying the chromosome abnormality. For the more common “balanced” or hidden translocation, the risk ranges from about 3 percent when the father is the carrier to about 12 percent when the mother is the carrier. If a parent carries a rare “21;21″ translocation, the risk for Down syndrome is 100 percent.
• Mosaicism — The risk is about the same as risk based on the mother’s age.

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