About Down Syndrome

Detailed information about Down syndrome

Down syndrome is named after Dr. John Langdon Down, a British physician, who was the first to describe it back in the 19th century, based on its external characteristics and the medical phenomena which occur with it. Only in 1959 was the genetic cause for the syndrome discovered – an extra no. 21 chromosome in the body's cells.

Down Syndrome is a condition in which excess genetic material (an extra no. 21 chromosome) causes a variety of typical physical and mental phenomena. This affects the child's development and his medical condition from the moment of his birth. There are substantial differences in the medical and functional conditions between every child with Down Syndrome. Giving medical, para-medical, and educational solutions as well as multi-factorial support to the children and their families can create a noticable improvement in many abilities and functions, and raise the chances for an independent life, rich community life and fitting into the work force.


  • Genetic explanation
  • Prevalence
  • Prenatal diagnostic tests for Down syndrome
  • Physical and mental characteristics of Down syndrome
  • The special character of Down syndrome children
  • A surprising angle about Down syndrome people's learning difficulties
  • The importance of constant medical supervision
  • In conclusion

Genetic explanation

Each cell in the human body carries a unique genetic code. In each and every cell in the human body, except the spermatozoon (sperm cells) and ovum (egg cells), has 46 chromosomes, which align in 23 pairs, and which are in fact the hereditary pattern according to which the fetus develops, physically and mentally. When the egg and sperm fuse, the created fetus receives genetic information from both parents: 23 chromosomes from his mother and 23 from his father, a total of 46 chromosomes.

In Down syndrome, the baby receives another no. 21 chromosome, mostly as a result of a problem in the separation mechanism of the chromosomes during the process of creating gametes (sperm or egg) in a parent's body. This causes the baby to have a triplet of no. 21 chromosomes (Trisomy) instead of a pair. This genetic addition is the cause for the variety of medical and mental problems in syndrome patients. The 21 Trisomy is the cause for Down syndrome in about 95% of the patients. The rest are as a result of a Mosaic (some body cells have a 21 Trisomy and some have a regular pair), or a Translocation (Besides the no. 21 pair chromosomes, another part of the 21 chromosome gets attached to a different chromosome, causing an excess of genetic material).

In the picture: Down syndrome under the microscope. All chromosomes are aligned in pairs, except for those labeled no. 21, in which there are 3 chromosomes instead of 2.


Down syndrome is the most common genetic syndrome of all, and it's prevalence is the same worldwide, also between all races and sexes.

The syndrome's prevalence is 1:800-1,000 live births – So is in Israel and in Western countries. The older the future mother is – the prevalence increases, especially past the age of 35. So, for example, at 25, the chance of a woman having a baby with Down syndrome is 1:1,600 births, at 30 it grows to around 1:1,000 births, but at 35 it rises steeply to 1:400 births.

At 40 years old, the chances of a woman for having a child with Down syndrome is 1 to every 100 births.

Prenatal diagnostic tests for Down syndrome

During pregnancy, there are two types of tests which allow early diagnosis of Down syndrome:

Prenatal Screening Tests which can evaluate the chances of the fetus having the syndrome. These tests are non-invasive. In addition, they cannot predict with certainty whether the fetus has Down syndrome or not. Mostly, these tests provide assistance to the doctor and future parents in deciding whether it is necessary to go through further diagnostic testing to identify the syndrome. The Screening tests include the Nuchal Translucency Screening test (performed at 11-14 weeks), Alpha-Fetoprotein (AFP) blood test (also known as part of the "triple-screen-test", performed at 15-20 weeks), and system screening and growth evaluation ultrasound tests which can give clues to the possibility of Down syndrome in the fetus.

Invasive diagnostic tests which accurately determine if the fetus has Down syndrome or not. These tests are 99% accurate in discovering Down syndrome and many other genetic disorders in the fetus. However, these invasive tests carry a 0.3-2% risk of losing the baby, according to the type of test. Because of the risk for causing abortion, invasive tests are not usually performed on every pregnant woman, but only in women over 35 years of age in which the chance for a fetus with Down syndrome is relatively higher.

The invasive diagnostic tests include Amniocentesis (Amniotic Fluid Test [AFT], performed 16-20 weeks into the pregnancy), placental biopsy (8-12 weeks into the pregnancy), or fetal blood sampling (from week 20 onwards).

Physical and mental characteristics of Down syndrome

Down syndrome children share a number of common clinical characteristics, but you rarely find all of them or even most of them in one single person with Down syndrome.

Some of the more common physical characteristics:
Facial characteristics: a flat facial profile, mostly a flat and wide nasal bridge while the nose is relatively small, a relatively round head, slanted eyes, small ears and a narrow structure of the auditory duct, smooth hair, a line crossing the width of the skin in the palm, a small mouth and a relatively large tongue.
General characteristics: small head, low muscle tone and muscle weakness, general limpness in the joint straps, small hands, short fingers, a large gap between the tow and the second finger in the foot.

These and other physical characteristics can lead to several problems common with Down syndrome children, for example: The low muscle tone and the significant limpness of the joints lead to substantial restrictions in movement, and so Down syndrome children, especially babies, can develop defective motor-movement control and can cause slow development of gentle motor skills and of coarser motor skills (crawling, sitting, standing, walking) relative to other children of their age. Today, using occupational therapy and physiotherapy, these abilities can be significantly improved.

The size of babies with Down syndrome at the time of birth is mostly small to average, but they tend to grow in a slower rate than their peers – which leads to them being smaller compared to others their age. There are special growth curves for Down syndrome babies.

Medical conditions related to Down Syndrome

Down syndrome patients have typical medical problems, involving various systems in the body, which might risk their health after birth, during their growth and development, and even in an older age.

For example, about 40% of Down syndrome children have cardiac birth defects and have a risk of developing respiratory problems.

Most children with Down syndrome suffer from visual and auditory problems: hearing problems can be caused by accumulation of fluid in the middle ear, as well as by the unique ear structure characteristic of this syndrome. Characteristic problems in the visual system include "Lazy Eye" (Amblyopia / ‎Strabismus) and Cataract. For these reasons, hearing tests and eye tests are required a short time after birth, to improve these systems' functioning and to discover defects and disorders as early as possible.

Additional commonly found medical problems in Down syndrome children include hypothyroidism (which in turn can cause a delay in development and obesity), short body height, digestion problems (a relatively high prevalence of internal blockages, constipation, Celiac), high susceptibility to infection, characteristic orthopedic problems and skin problems. Most of the medical conditions described above require early diagnosis and early and continuous treatment, in order to improve the medical, developmental and functional condition.

The life expectancy of a child born with Down syndrome has significantly risen in the past few years, and it now stands at 55 years. We predict an increase in the life expectancy with the progress of modern medicine and the general improvement in health services. About adults with Down syndrome, we will only say that typical old-age problems, such as Dementia, Alzheimer's, and Osteoporosis, appear relatively early and in high prevalence compared to the general population.

The syndrome also affects a variety of the children's mental functions – language, speech, pronunciation, expressiveness, comprehension, communication, reading and writing and more. It is acceptable to say that Down syndrome patients suffer from different degrees of mental retardation. However, it is important to remember that many intelligence tests depend mostly on the subjects' expressive abilities, and because Down syndrome patients have typical problem in that area, their IQ grades can be lower than they deserve.

The external and internal physical attributes cannot predict the child's future mental abilities.

The special character of Down syndrome children

Typically, Down syndrome children have a pleasant and convenient temperament, and they are friendly and make friends easily. In addition it is known they are naïve, they have a good wide heart, and they have keen senses for everything concerning emotional intelligence.

These traits allow Down syndrome patients to integrate themselves in the education system, the labor force and the community. Down syndrome children can receive aid from early intervention services in order to fully extract their hidden potential. Because of various reasons, it can be expected that the chances of the children who receive good medical care and a supporting treatment from their environment could develop social skills more easily, fit into different frameworks (school, society, work) and also make independent decisions affecting their lives.

A surprising angle about Down syndrome people's learning difficulties
Typically, children with Down syndrome suffer from significant learning disabilities throughout their childhood. There are children with Down syndrome who succeed in their schooling and advance to independent adult life, including independent living, a job, social life and family life. How successful they are depend on their medical condition, their mental and physical abilities, and the support of the family, the medical system and society.

The great resemblance between Down syndrome children can be misleading. In time, it will become apparent that these children are very different from each other and each and every one of them is special and requires individual treatment and care.

Children with Down syndrome might develop a motivational decrease for studying and developing because of society's treatment of them as well as their own treatment of themselves. Doing so, the child contributes to their own developing cognitive ailment, and they do so by adopting negative learning behaviors. It can be said that the child makes the learning process harder on himself more than many other factors do. When the child experiences many failures regarding learning abilities, combined with society's low expectations of him, it is not a surprise that he tries to avoid new challenges and new problem solving as much as possible.

This becomes apparent mainly from the growing use of avoidance strategies when the child faces a mental challenge.

Thus, psychological factors and not only physical ones have a meaningful role in everything regarding the mental development of children with Down syndrome, and those can be treated.

The importance of constant medical supervision

Today, there are about 6,900 people with Down syndrome living in Israel. The Down Syndrome Medical Center at Hadassah Mt. Scopus, Run by Dr. Ariel Tenenbaum, was erected for treatment, follow-up and improvement of the health and quality of life of these people.

The population of Down syndrome children has typical problems which require close supervision and individual treatment. The Medical Center at Hadassah Mt. Scopus concentrates the entire complex of necessary medical and para-medical follow-up and treatment, emphasizing promotion of health, preventative medicine, treatment of acute and chronic problems, close supervision and promoting integration in regular educational structures and in the work force.

In the center there is a multi-disciplinary team of doctors, nurses and paramedical professionals giving a wholesome address to the complex problems of Down syndrome children. We believe that multi-systemic support is the key to the promotion of children in the functional sense, to the extraction of the potential in each child and to the achieving of full and satisfying community and society life.

In Conclusion

Down syndrome is a condition in which there is excess genetic material. This genetic addition, which is in fact an excess no. 21 chromosome (all or part of it, in all or part of the body cells), causes physical and cognitive delays connected with the syndrome. Down syndrome is the most prevalent genetic disorder of all, and its prevalence is the same worldwide, across all races and sexes.

Down syndrome has typical physical and mental characteristics, but onlyseldom all of them or even most of them are found in one single person. If we study the character of children with the syndrome, we will find they have a pleasant and convenient temperament and a special character. They are friendly, sensitive and have a sharp and developed emotional intelligence (EQ). These traits assist them in fitting in as a pat of society and the community rather successfully.

The discernible differences concerning the medical condition and the developmental level between Down syndrome children are caused, among other things, by the different medical treatments and the support of each child's environment. Multi-systemic support (medical, educational, environmental) can bring many improvements in the children's function, allowing them to extract their maximum potential and increases their chances to live a rich, independent community life.