Classification and external resources
|Boy with Down syndrome assembling a bookcase|
Down syndrome or trisomy 21 (or Down's syndrome in British English and WHO ICD) is a chromosomal disorder caused by the presence of all or part of an extra 21st chromosome. The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify Diseases The International Statistical Classification of Diseases and Related Health Problems 10th Revision ( ICD -10) is a coding of diseases and signs symptoms abnormal findings Q00-Q89 - Congenital malformations and deformations (Q00-Q07 Nervous system ( Anencephaly and similar malformations The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify Diseases The following is a list of codes for International Statistical Classification of Diseases and Related Health Problems. The Mendelian Inheritance in Man project is a Database that catalogues all the known Diseases with a genetic component, and—when possible—links them The Diseases Database is a free Website that provides information about the relationships between medical conditions Symptoms, and Medications. MedlinePlus, with the MedlinePlus Medical Encyclopedia, is a website network containing Health information from the world's largest medical Library eMedicine is an online clinical medical knowledge base that was founded in 1996 by Scott Plantz and Richard Lavely two medical doctors Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books The International Statistical Classification of Diseases and Related Health Problems (most commonly known by the abbreviation ICD) provides codes to classify Diseases A chromosome abnormality reflects an abnormality of chromosome number or structure Chromosome 21 is one of the 23 pairs of Chromosomes in Humans People normally have two copies of this chromosome It is named after John Langdon Down, the British doctor who described the syndrome in 1866. John Langdon Haydon Down ( November 18, 1828 - October 7, 1896) was a British doctor best known for his description of what The year 1866 in Science and Technology involved some significant events listed below The disorder was identified as a chromosome 21 trisomy by Jérôme Lejeune in 1959. Jérôme Jean Louis Marie Lejeune ( Montrouge, France; June 26 1926 - April 3 1994) was a French Catholic The condition is characterized by a combination of major and minor differences in structure. Often Down syndrome is associated with some impairment of cognitive ability and physical growth as well as facial appearance. Cognition is a concept used in different ways by different disciplines but is generally accepted to mean the process of awareness or thought Child development refers to the biological and psychological changes that occur in human beings between birth and the end of Adolescence, as the individual Down syndrome can be identified during pregnancy or at birth.
Individuals with Down syndrome tend to have a lower than average cognitive ability, often ranging from mild to moderate learning disabilities. In the United States and Canada, the term learning disability (LD refers to a group of disorders that affect a broad range of academic and functional skills including A small number have severe to profound mental disability. The incidence of Down syndrome is estimated at 1 per 800 to 1,000 births, although these statistics are heavily influenced by the age of the mother. Incidence is a measure of the risk of developing some new condition within a specified period of time Other factors may also play a role.
Many of the common physical features of Down syndrome also appear in people with a standard set of chromosomes. They may include a single transverse palmar crease (a single instead of a double crease across one or both palms, also called the Simian crease), an almond shape to the eyes caused by an epicanthic fold of the eyelid, upslanting palpebral fissures, shorter limbs, poor muscle tone, a larger than normal space between the big and second toes, and protruding tongue. In humans a single transverse palmar crease is a single crease that extends across the palm of the Hand, formed by the fusion of the two Palmar creases that people Palpebral fissure is the Anatomic name for the separation between the upper and lower Eyelids In the adult this measures about 10mm vertically and 30 mm horizontally Health concerns for individuals with Down syndrome include a higher risk for congenital heart defects, gastroesophageal reflux disease, recurrent ear infections, obstructive sleep apnea, and thyroid dysfunctions. A congenital heart defect (CHD is a defect in the structure of the Heart and Great vessels of a Newborn. Gastroesophageal reflux disease ( American English and Canadian English) or Gastro-oesophageal reflux disease ( British English, Hiberno-English Otitis is a general term for inflammation or infection of the ear in both humans and other animals Obstructive sleep apnea (OSA is a common Sleep apnea caused by obstruction of the airway The thyroid is one of the largest Endocrine glands in the body
Early childhood intervention, screening for common problems, medical treatment where indicated, a conducive family environment, and vocational training can improve the overall development of children with Down syndrome. Early childhood intervention is a support system for children with developmental disabilities or delays and their families Although some of the physical genetic limitations of Down syndrome cannot be overcome, education and proper care will improve quality of life. 
Individuals with Down syndrome may have some or all of the following physical characteristics: oblique eye fissures with epicanthic skin folds on the inner corner of the eyes, muscle hypotonia (poor muscle tone), a flat nasal bridge, a single palmar fold, a protruding tongue (due to small oral cavity, and an enlarged tongue near the tonsils), a short neck, white spots on the iris known as Brushfield spots, excessive joint laxity including atlanto-axial instability, congenital heart defects, excessive space between large toe and second toe, a single flexion furrow of the fifth finger, and a higher number of ulnar loop dermatoglyphs. The iris consists of Pigmented Fibrovascular tissue known as a stroma. Brushfield spots are small white or grayish/brown spots on the periphery of the iris in the human Eye due to aggregation of Hypotonia is a condition of abnormally low Muscle tone (the amount of tension or resistance to movement in a muscle often involving reduced muscle strength In humans a single transverse palmar crease is a single crease that extends across the palm of the Hand, formed by the fusion of the two Palmar creases that people Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain Brushfield spots are small white or grayish/brown spots on the periphery of the iris in the human Eye due to aggregation of The hallux, commonly referred to as the big toe (also as great toe or thumb toe) even though it's not actually the biggest toe on the foot of some In Anatomy, flexion is a position that is made possible by the joint angle decreasing Dermatoglyphics (from Ancient Greek derma = "skin" Glyph = "carving" is the scientific study of Fingerprints The term was coined by Most individuals with Down syndrome have mental retardation in the mild (IQ 50–70) to moderate (IQ 35–50) range, with individuals having Mosaic Down syndrome (explained below) typically 10–30 points higher. Mental retardation is a generalized triarchic disorder characterized by subaverage cognitive functioning and deficits in two or more adaptive behaviors with onset before the age An Intelligence Quotient or IQ is a score derived from one of several different Standardized tests attempting to measure Intelligence.  In addition, individuals with Down syndrome can have serious abnormalities affecting any body system. They also may have a broad head and a very round face.
Down syndrome is a chromosomal abnormality characterized by the presence of an extra copy of genetic material on the 21st chromosome, either in whole (trisomy 21) or part (such as due to translocations). Chromosome 21 is one of the 23 pairs of Chromosomes in Humans People normally have two copies of this chromosome Aneuploidy is defined as an abnormal number of Chromosomes Syndromes caused by an extra or missing chromosome are among the most widely recognized Genetic disorders In Genetics, a chromosome translocation is a Chromosome abnormality caused by rearrangement of parts between nonhomologous Chromosomes. The effects of the extra copy vary greatly among people, depending on the extent of the extra copy, genetic history, and pure chance. Down syndrome occurs in all human populations, and analogous effects have been found in other species such as chimpanzees and mice. Recently, researchers have created transgenic mice with most of human chromosome 21 (in addition to the normal mouse chromosomes). This article is about organisms which have been genetically modified  The extra chromosomal material can come about in several distinct ways. A typical human karyotype is designated as 46,XX or 46,XY, indicating 46 chromosomes with an XX arrangement typical of females and 46 chromosomes with an XY arrangement typical of males. 
Trisomy 21 (47,XX,+21) is caused by a meiotic nondisjunction event. In Biology or life science meiosis (pronounced my-oh-sis is a process of reductional division in which the number of chromosomes per cell is cut in half Nondisjunction is the failure of chromosome pairs to separate properly during cell division With nondisjunction, a gamete (i. A gamete (from Ancient Greek γαμέτης; translated gamete = wife gametes = husband is a cell that fuses with another gamete e. , a sperm or egg cell) is produced with an extra copy of chromosome 21; the gamete thus has 24 chromosomes. When combined with a normal gamete from the other parent, the embryo now has 47 chromosomes, with three copies of chromosome 21. An embryo (from Greek:, plural, lit "that which grows" from en- "in" + bryein "to swell be full" is a multicellular Trisomy 21 is the cause of approximately 95% of observed Down syndromes, with 88% coming from nondisjunction in the maternal gamete and 8% coming from nondisjunction in the paternal gamete. 
Trisomy 21 is caused prior to conception, and all cells in the body are affected. However, when some of the cells in the body are normal and other cells have trisomy 21, it is called Mosaic Down syndrome (46,XX/47,XX,+21). In Medicine ( Genetics) a mosaic or mosaicism denotes the presence of two populations of cells with different Genotypes in one  This can occur in one of two ways: A nondisjunction event during an early cell division in a normal embryo leads to a fraction of the cells with trisomy 21; or a Down syndrome embryo undergoes nondisjunction and some of the cells in the embryo revert to the normal chromosomal arrangement. There is considerable variability in the fraction of trisomy 21, both as a whole and among tissues. This is the cause of 1–2% of the observed Down syndromes. 
The extra chromosome 21 material that causes Down syndrome may be due to a Robertsonian translocation. Robertsonian translocation is a common form of chromosomal rearrangement that occurs in the five acrocentric human Chromosome pairs namely 13 14 15 21 and 22 In this case, the long arm of chromosome 21 is attached to another chromosome, often chromosome 14 (45,XX, t(14;21q)) or itself (called an isochromosome, 45,XX, t(21q;21q)). Chromosome 14 is one of the 23 pairs of Chromosomes in Humans People normally have two copies of this chromosome An isochromosome is a Chromosome that has lost one of its arms and replaced it with an exact copy of the other arm These parents are phenotypically normal. Normal disjunctions leading to gametes have a significant chance of creating a gamete with an extra chromosome 21, producing a child with Down syndrome. Translocation Down syndrome is often referred to as familial Down syndrome. It is the cause of 2–3% of observed cases of Down syndrome.  It does not show the maternal age effect, and is just as likely to have come from fathers as mothers.
Rarely, a region of chromosome 21 will undergo a duplication event. This will lead to extra copies of some, but not all, of the genes on chromosome 21 (46,XX, dup(21q)).  If the duplicated region has genes that are responsible for Down syndrome physical and mental characteristics, such individuals will show those characteristics. This cause is very rare and no rate estimates are available.
The incidence of Down syndrome is estimated at 1 per 800 to 1 per 1000 births.  In 2006, the Center for Disease Control estimated the rate as 1 per 733 live births in the United States (5429 new cases per year).  Approximately 95% of these are trisomy 21. Down syndrome occurs in all ethnic groups and among all economic classes.
Maternal age influences the chances of conceiving a baby with Down syndrome. The maternal age effect describes the exponentially increasing risks for numerical chromosomal abnormalities among a prospective mother's Gametes as she ages At maternal age 20 to 24, the probability is 1/1562; at age 35 to 39 the probability is 1/214, and above age 45 the probability is 1/19.  Although the probability increases with maternal age, 80% of children with Down syndrome are born to women under the age of 35, reflecting the overall fertility of that age group. Recent data also suggest that paternal age, especially beyond 42, also increases the risk of Down Syndrome manifesting in pregnancies in older mothers. 
Current research (as of 2-19-8) has shown that Down syndrome is due to a random event during the formation of sex cells or pregnancy. There has been no evidence that it is due to parental behavior or environmental factors.
Pregnant women can be screened for various complications during pregnancy. Many standard prenatal screens can discover Down syndrome. Genetic counseling along with genetic testing, such as amniocentesis, chorionic villus sampling (CVS), or percutaneous umbilical cord blood sampling (PUBS) are usually offered to families who may have an increased chance of having a child with Down syndrome, or where normal prenatal exams indicate possible problems. Genetic counseling is the process by which patients or relatives at risk of an inherited disorder are advised of the consequences and nature of the disorder the probability of developing Genetic testing allows the genetic Diagnosis of vulnerabilities to inherited Diseases, and can also be used to determine a person's Ancestry. Amniocentesis (also referred to as amniotic fluid test or AFT) is a medical procedure used in Prenatal diagnosis of genetic abnormalities and fetal Chorionic villus sampling (CVS is a form of Prenatal diagnosis to determine chromosomal or Genetic disorders in the Fetus. Genetic screens are often performed on pregnant women older than 30 or 35.
Amniocentesis and CVS are considered invasive procedures, in that they involve inserting instruments into the uterus, and therefore carry a small risk of causing fetal injury or miscarriage. There are several common non-invasive screens that can indicate a fetus with Down syndrome. These are normally performed in the late first trimester or early second trimester. Due to the nature of screens, each has a significant chance of a false positive, suggesting a fetus with Down syndrome when, in fact, the fetus does not have this genetic abnormality. In Statistics, the terms Type I error (also α error, or false positive) and type II error ( β error, or a false negative Screen positives must be verified before a Down syndrome diagnosis is made. Common screening procedures for Down syndrome are given in Table 1.
|Screen||When performed (weeks gestation)||Detection rate||False positive rate||Description|
|Triple screen||15–20||75%||8. Gestation is the carrying of an Embryo or Fetus inside a Female Viviparous Animal. The triple test, also called triple screen, the Kettering test or the Bart's test is an investigation performed during Pregnancy (usually the second trimester 5%||This test measures the maternal serum alpha feto protein (a fetal liver protein), estriol (a pregnancy hormone), and human chorionic gonadotropin (hCG, a pregnancy hormone). Alpha-fetoprotein ( AFP) is a molecule produced in the developing Embryo Estriol (also oestriol) is one of the three main Estrogens produced by the human body Human chorionic gonadotropin ( hCG) is a Glycoprotein Hormone produced in Pregnancy that is made by the Embryo soon after conception |
|Quad screen||15–20||79%||7. The triple test, also called triple screen, the Kettering test or the Bart's test is an investigation performed during Pregnancy (usually the second trimester 5%||This test measures the maternal serum alpha feto protein (a fetal liver protein), estriol (a pregnancy hormone), human chorionic gonadotropin (hCG, a pregnancy hormone), and high inhibin-Alpha (INHA). Inhibin is a peptide that is an inhibitor of FSH Synthesis and Secretion, and participates in the regulation of the Menstrual cycle |
|AFP/free beta screen||13–22||80%||2. 8%||This test measures the alpha feto protein, produced by the fetus, and free beta hCG, produced by the placenta. The placenta is an Ephemeral organ present in placental Vertebrates, such as Eutherial Mammals and Sharks during Gestation|
|Nuchal translucency/free beta/PAPPA screen||10–13. 5||91%||5%||Uses ultrasound to measure Nuchal Translucency in addition to the freeBeta hCG and PAPPA (pregnancy-associated plasma protein A). Not to be confused with Supersonic. Ultrasound is cyclic Sound pressure with a Frequency greater than the upper A nuchal scan is a sonographic prenatal screening scan ( Ultrasound) to help identify higher risks of Down syndrome in developing babies particularly for Pregnancy-associated plasma protein A pappalysin 1, also known as PAPPA, is a protein used in screening tests for Down syndrome. NIH has confirmed that this first trimester test is more accurate than second trimester screening methods. |
Even with the best non-invasive screens, the detection rate is 90%–95% and the rate of false positive is 2%–5%. False positives can be caused by undetected multiple fetuses (very rare with the ultrasound tests), incorrect date of pregnancy, or normal variation in the proteins.
Confirmation of screen positive is normally accomplished with amniocentesis or chorionic villus sampling (CVS). Amniocentesis is an invasive procedure and involves taking amniotic fluid from the amniotic sac and identifying fetal cells. Amniocentesis (also referred to as amniotic fluid test or AFT) is a medical procedure used in Prenatal diagnosis of genetic abnormalities and fetal Amniotic fluid or liquor amnii is the nourishing and protecting liquid contained by the Amnion of a pregnant woman The lab work can take several weeks but will detect over 99. 8% of all numerical chromosomal problems with a very low false positive rate. 
Due to the low incidence of Down syndrome, a vast majority of early screen positives are false.  Since false positives typically prompt an amniocentesis to confirm the result, and the amniocentesis carries a small risk of inducing miscarriage, there is a slight risk of miscarrying a healthy fetus. Miscarriage or spontaneous abortion is the natural or spontaneous end of a Pregnancy at a stage where the embryo or fetus is incapable of surviving generally defined (The added miscarriage risk from an amniocentesis is traditionally quoted as 0. 5%, but recent studies suggest that it may be considerably smaller (0. 06%), not statistically different from zero. )
A 2002 literature review of elective abortion rates found that 91–93% of pregnancies with a diagnosis of Down syndrome were terminated.  Physicians and ethicists are concerned about the ethical ramifications of this.  Conservative commentator George Will called it "eugenics by abortion". Conservatism in the United States includes a variety of political ideologies including Fiscal conservatism, Supply-side economics, Social conservatism An editorial, leader (UK or leading article (UK is an article in a Newspaper or Magazine that expresses the opinion of the Editor George Frederick Will (born May 4, 1941) is a Pulitzer Prize -winning conservative American newspaper Columnist, journalist Eugenics is a social Philosophy which advocates the improvement of Human Hereditary traits through various forms of intervention Abortion in the United States is a highly-charged issue involving significant political and ethical debate  British peer Brian Rix stated that "alas, the birth of a child with Down's syndrome is still considered by many to be an utter tragedy" and that the "ghost of the biologist Sir Francis Galton, who founded the eugenics movement in 1885, still stalks the corridors of many a teaching hospital". The Peerage of the United Kingdom comprises most Peerages created in the United Kingdom of Great Britain and Ireland after the Act of Union in 1801 when Brian Norman Roger Rix Baron Rix, CBE (born January 27, 1924) is an English Actor and charity worker A biologist is a Scientist devoted to and producing results in Biology through the study of Organisms Typically biologists study organisms and their relationship Sir Francis Galton FRS ( 16 February 1822 &ndash 17 January 1911) half-cousin of Charles Darwin, was an Eugenics is a social Philosophy which advocates the improvement of Human Hereditary traits through various forms of intervention A teaching hospital is a Hospital that in addition to delivering medical care to patients also provides Clinical education and training to future and current doctors  Doctor David Mortimer has argued in Ethics & Medicine that "Down's syndrome infants have long been disparaged by some doctors and government bean counters. " Some members of the disability rights movement "believe that public support for prenatal diagnosis and abortion based on disability contravenes the movement's basic philosophy and goals. The disability rights movement aims to improve the Quality of life of people with disabilities. "
A 1998 study of Finnish doctors found that "Only very few, pediatricians somewhat more often, thought that Down's syndrome is not a good enough reason for pregnancy termination, but more (15-21%) thought that current prenatal screenings in general are (partly) based on eugenic thinking. Finland, officially the Republic of Finland ( is a Nordic country situated in the Fennoscandian region of northern Europe. Pediatrics (also spelled paediatrics) is the branch of Medicine that deals with the medical care of Infants Children and Adolescents Eugenics is a social Philosophy which advocates the improvement of Human Hereditary traits through various forms of intervention "
Cognitive development in children with Down syndrome is quite variable. The Theory of Cognitive Development (one of the most historically influential theories was developed by Jean Piaget, a Swiss Philosopher (1896–1980 It is not currently possible at birth to predict the capabilities of any individual reliably, nor are the number or appearance of physical features predictive of future ability. The identification of the best methods of teaching each particular child ideally begins soon after birth through early intervention programs.  Since children with Down syndrome have a wide range of abilities, success at school can vary greatly, which underlines the importance of evaluating children individually. The cognitive problems that are found among children with Down syndrome can also be found among typical children. Therefore, parents can use general programs that are offered through the schools or other means. Language skills show a difference between understanding speech and expressing speech. It is not uncommon for children with Down Syndrome to have a speech delay, although it is common for them to need speech therapy to help with expressive language.  Fine motor skills are delayed and often lag behind gross motor skills and can interfere with cognitive development. Fine motor skills can be defined as coordination of small Muscle movements which occur e The term gross motor skills refers to the abilities usually acquired during infancy and early childhood as part of a child's motor development Gross Motor Skills can be affected anywhere from minor to major. Some children will walk at around 2 while others around 4. A physical therapist or APE will help a child with this. 
Individuals with Down syndrome differ considerably in their language and communication skills. It is routine to screen for middle ear problems and hearing loss; low gain hearing aids or other amplification devices can be useful for language learning. Early communication intervention fosters linguistic skills. Language assessments can help profile strengths and weaknesses; for example, it is common for receptive language skills to exceed expressive skills. Individualized speech therapy can target specific speech errors, increase speech intelligibility, and in some cases encourage advanced language and literacy. Augmentative and alternative communication (AAC) methods, such as pointing, body language, objects, or graphics are often used to aid communication. Augmentative and alternative communication (AAC refers "to an area of research clinical and educational practice Relatively little research has focused on the effectiveness of communications intervention strategies. 
In education, mainstreaming of children with Down syndrome is becoming less controversial in many countries. Mainstreaming in the context of education is a term that refers to the practice of educating students with special needs in regular classes during specific time periods based on their For example, there is a presumption of mainstream in many parts of the UK. Mainstreaming is the process whereby students of differing abilities are placed in classes with their chronological peers. Children with Down syndrome may not age emotionally/socially and intellectually at the same rates as children without Down syndrome, so over time the intellectual and emotional gap between children with and without Down syndrome may widen. Complex thinking as required in sciences but also in history, the arts, and other subjects can often be beyond the abilities of some, or achieved much later than in other children. Therefore, children with Down syndrome may benefit from mainstreaming provided that some adjustments are made to the curriculum. 
Some European countries such as Germany and Denmark advise a two-teacher system, whereby the second teacher takes over a group of children with disabilities within the class. Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. The Kingdom of Denmark ( ˈd̥ænmɑɡ̊ (archaic ˈd̥anmɑːɡ̊ commonly known as Denmark, is a country in the Scandinavian region of northern Europe A popular alternative is cooperation between special schools and mainstream schools. A special school is a school catering to students who have Special educational needs e In cooperation, the core subjects are taught in separate classes, which neither slows down the typical students nor neglects the students with disabilities. Social activities, outings, and many sports and arts activities are performed together, as are all breaks and meals. 
The medical consequences of the extra genetic material in Down syndrome are highly variable and may affect the function of any organ system or bodily process. Down syndrome is a genetic disease resulting from the presence of all or part of an extra 21st chromosome ( Trisomy 21) The health aspects of Down syndrome encompass anticipating and preventing effects of the condition, recognizing complications of the disorder, managing individual symptoms, and assisting the individual and his/her family in coping and thriving with any related disability or illnesses. 
Down syndrome can result from several different genetic mechanisms. This results in a wide variability in individual symptoms due to complex gene and environment interactions. Prior to birth, it is not possible to predict the symptoms that an individual with Down syndrome will develop. Some problems are present at birth, such as certain heart malformations. Others become apparent over time, such as epilepsy.
The most common manifestations of Down syndrome are the characteristic facial features, cognitive impairment, congenital heart disease (typically a ventricular septal defect), hearing deficits (maybe due to sensory-neural factors, or chronic serous otitis media, also known as Glue-ear), short stature, thyroid disorders, and Alzheimer's disease. A congenital heart defect (CHD is a defect in the structure of the Heart and Great vessels of a Newborn. A ventricular septal defect ( VSD) is a defect in the Ventricular septum, the wall dividing the left and right ventricles of the Heart. Otitis media is Inflammation of the Middle ear, or middle ear infection (the word otitis is Greek and it means “inflammation of the ear” and media Short stature refers to a height of a human being which is below expected Alzheimer's disease ( AD) also called Alzheimer disease or simply Alzheimer's, is the most common form of Dementia. Other less common serious illnesses include leukemia, immune deficiencies, and epilepsy. Leukemia or leukaemia (Greek leukos λευκός, "white" aima αίμα, "blood" is a Cancer of the Blood In Medicine, immunodeficiency (or immune deficiency) is a state in which the Immune system 's ability to fight Infectious disease is compromised Epilepsy is a common chronic Neurological disorder that is characterized by recurrent unprovoked seizures.
However, health benefits of Down syndrome include greatly reduced incidence of many common malignancies except leukemia and testicular cancer — although it is, as yet, unclear whether the reduced incidence of various fatal cancers among people with Down syndrome is as a direct result of tumor-suppressor genes on chromosome 21 (such as Ets2), because of reduced exposure to environmental factors that contribute to cancer risk, or some other as-yet unspecified factor. In Epidemiology, environmental factors are those determinants of disease that are not transmitted genetically. In addition to a reduced risk of most kinds of cancer, people with Down syndrome also have a much lower risk of hardening of the arteries and diabetic retinopathy. Atherosclerosis is a Disease affecting arterial Blood vessels It is a chronic inflammatory response in the walls of arteries in large part due to the accumulation Diabetic retinopathy is Retinopathy (damage to the Retina) caused by complications of Diabetes mellitus, which can eventually lead to Blindness 
These factors can contribute to a shorter life expectancy for people with Down syndrome. One study, carried out in the United States in 2002, showed an average lifespan of 49 years, with considerable variations between different ethnic and socio-economic groups. The United States of America —commonly referred to as the  However, in recent decades, the life expectancy among persons with Down Syndrome has increased significantly up from 25 years in 1980. The causes of death have also changed, with chronic neurodegenerative diseases becoming more common as the population ages.
Down syndrome is “a developmental abnormality characterized by trisomy of human chromosome 21" (Nelson 619). Research of Down syndrome-related genes is based on studying the Genes located on chromosome 21 A trisomy is a form of Aneuploidy with the presence of three copies instead of the normal two of a particular Chromosome. Chromosome 21 is one of the 23 pairs of Chromosomes in Humans People normally have two copies of this chromosome The extra copy of chromosome-21 leads to an over expression of certain genes located on chromosome-21. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance
Research by Arron et al shows that some of the phenotypes (displayed genetic characteristics), associated with Down Syndrome can be related to the dysregulation of gene-regulating proteins (596). A phenotype is any observable characteristic of an Organism, such as its morphology, Development, biochemical or physiological properties The gene-regulating proteins bind to DNA and initiate certain segments of DNA to be replicated for the production of a certain protein (Arron et al. Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known 596). The gene-regulator in interest is called NFATc. Its activities are controlled by two proteins, DSCR1 and DYRK1A; these genes are located on chromosome-21 (Epstein 582). In people with Down Syndrome, these proteins have 1. 5 times greater concentration than normal (Arron et al. 597). The elevated levels of DSCR1 and DYRK1A mean that most of the NFATc is located in the cytoplasm rather than in the nucleus promoting DNA replication which will produce vital proteins (Epstein 583). The cytoplasm is the contents of a cell that is enclosed within the Plasma membrane. In Cell biology, the nucleus (pl nuclei; from Latin la ''nucleus'' or la ''nuculeus'' "little nut" or kernel is a membrane-enclosed DNA replication is the process of copying a double-stranded DNA molecule to form two double-stranded molecules
This dysregulation was discovered by testing in transgenic mice. The mice had segments of their chromosomes duplicated to simulate a human chromosome-21 trisomy (Arron et al. 597). A common characteristic of Down Syndrome is poor muscle tone, so a test involving the grip strength of the mice showed that the genetically modified mice had a significantly weaker grip (Arron et al. 596). The mice squeezed a probe with a paw; the modified mice displayed a . 2 Newton (measurement of force) weaker grip (Arron et al. 596). Down syndrome is also characterized by increased socialization. Both modified and unmodified mice were observed for social interaction. The modified mice showed as many as 25% more interactions per time period as the unmodified mice (Arron et al. 596).
The genes that may be responsible for the phenotypes associated may be located proximal to 21q22. 3. Testing by Olson et al, in transgenic mice show the duplicated genes presumed to cause the phenotypes are not enough to cause the exact features. While the mice had sections of multiple genes duplicated to approximate a human chromosome-21 triplication, they only showed slight craniofacial abnormalities (688-690). The transgenic mice were compared to mice that had no gene duplication by measuring distances on various points on their skeletal structure and comparing them to the normal mice (Olson et al. 687). The exact characteristics of Down Syndrome were not observed, so more genes involved for Down Syndrome phenotypes have to be located elsewhere.
Reeves et al, using 250 clones of chromosome-21 and specific gene markers, were able to map the gene in mutated bacteria. The testing had 99. 7% coverage of the gene with 99. 9995% accuracy due to multiple redundancies in the mapping techniques. In the study 225 genes were identified (311-313).
The search for major genes that may be involved in Down syndrome symptoms is normally in the region 21q21–21q22. 3. However, studies by Reeves et al. show that 41% of the genes on chromosome-21 have no functional purpose, and only 54% of functional genes have a known protein sequence. Functionality of genes was determined by a computer using exon prediction analysis (312). An exon is a Nucleic acid sequence that is represented in the mature form of an RNA molecule after a portions of a precursor RNA Introns have been Exon sequence was obtained by the same procedures of the chromosome-21 mapping. An exon is a Nucleic acid sequence that is represented in the mature form of an RNA molecule after a portions of a precursor RNA Introns have been
Research has led to an understanding that two genes located on chromosome-21, that code for proteins that control gene regulators, DSCR1 and DYRK1A can be responsible for some of the phenotypes associated with Down Syndrome. DSCR1 and DYRK1A cannot be blamed outright for the symptoms; there are a lot of genes that have no known purpose. Much more research would be needed to produce any appropriate or ethically acceptable treatment options.
Recent use of transgenic mice to study specific genes in the Down syndrome critical region has yielded some results. This article is about organisms which have been genetically modified A mouse (plural mice) is a small Animal that belongs to one APP is an Amyloid beta A4 precursor protein. It is suspected to have a major role in cognitive difficulties.  Another gene, ETS2 is Avian Erythroblastosis Virus E26 Oncogene Homolog 2. Researchers have "demonstrated that over-expression of ETS2 results in apoptosis. Transgenic mice over-expressing ETS2 developed a smaller thymus and lymphocyte abnormalities, similar to features observed in Down syndrome. "
Vitamin supplements, in particular supplemental antioxidants and folinic acid, have been shown to be ineffective in the treatment of Down syndrome. 
Advocates for people with Down syndrome point to various factors, such as additional educational support and parental support groups to improve parenting knowledge and skills. There are also strides being made in education, housing, and social settings to create environments which are accessible and supportive to people with Down syndrome. In most developed countries, since the early twentieth century many people with Down syndrome were housed in institutions or colonies and excluded from society. However, since the early 1960s parents and their organizations (such as MENCAP), educators and other professionals have generally advocated a policy of inclusion, bringing people with any form of mental or physical disability into general society as much as possible. In many countries, people with Down syndrome are educated in the normal school system; there are increasingly higher-quality opportunities to move from special (segregated) education to regular education settings.
Despite these changes, the additional support needs of people with Down syndrome can still pose a challenge to parents and families. Although living with family is preferable to institutionalization, people with Down syndrome often encounter patronizing attitudes and discrimination in the wider community.
The first World Down Syndrome Day was held on 21 March 2006. World Down Syndrome Day (WDSD is on 21 March. On this day Down syndrome organizations throughout the world organize and participate in events to raise public Events 630 - Byzantine emperor Heraclius restores the True Cross to Jerusalem. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. The day and month were chosen to correspond with 21 and trisomy respectively. It was proclaimed by European Down Syndrome Association during their European congress in Palma de Mallorca (febr. 2005). In the United States, the National Down Syndrome Society observes Down Syndrome Month every October as "a forum for dispelling stereotypes, providing accurate information, and raising awareness of the potential of individuals with Down syndrome. " In South Africa, Down Syndrome Awareness Day is held every October 20. The Republic of South Africa (also known by other official names) is a country located at the southern tip of the continent of Africa  Organizations such as Special Olympics Hawaii provide year-round sports training for individuals with intellectual disabilities such as down syndrome.
English physician John Langdon Down first characterized Down syndrome as a distinct form of mental disability in 1862, and in a more widely published report in 1866. John Langdon Haydon Down ( November 18, 1828 - October 7, 1896) was a British doctor best known for his description of what  Due to his perception that children with Down syndrome shared physical facial similarities (epicanthal folds) with those of Blumenbach's Mongolian race, Down used terms derived from prevailing ethnic theory. Johann Friedrich Blumenbach ( May 11, 1752 – January 22, 1840) was a German doctor and Physiologist, 
By the 20th century, Down Syndome had become the most recognizable form of mental disability. Most individuals with Down syndrome were institutionalized, few of the associated medical problems were treated, and most died in infancy or early adult life. With the rise of the eugenics movement, 33 of the (then) 48 U.S. states and several countries began programs of forced sterilization of individuals with Down syndrome and comparable degrees of disability. A US state is any one of the fifty subnational entities of the United States of America that share Sovereignty with the federal government The ultimate expression of this type of public policy was the so called euthanasia program "Action T-4" in Nazi Germany, a program of systematic murder. Action T4 (Aktion T4 was a program in Nazi Germany spanning October 1939 until August 1941 during which physicians killed 70273 peoplespecified in Hitler's Nazi Germany and the Third Reich are the common English names for Germany under the regime of Adolf Hitler and the National Socialist German Workers Court challenges, scientific advances and public revulsion led to discontinuation or repeal of such sterilisation programs during the decades after World War II. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including
Until the middle of the 20th century, the cause of Down syndrome remained unknown. However, the presence in all races, the association with older maternal age, and the rarity of recurrence had been noticed. Standard medical texts assumed it was caused by a combination of inheritable factors which had not been identified. Other theories focused on injuries sustained during birth. 
With the discovery of karyotype techniques in the 1950s, it became possible to identify abnormalities of chromosomal number or shape. A karyotype is the characteristic Chromosome complement of a Eukaryote Species. In 1959, Jérôme Lejeune discovered that Down syndrome resulted from an extra chromosome.  The extra chromosome was subsequently labeled as the 21st, and the condition as trisomy 21. Chromosome 21 is one of the 23 pairs of Chromosomes in Humans People normally have two copies of this chromosome
In 1961, nineteen geneticists wrote to the editor of The Lancet suggesting that Mongolian idiocy had "misleading connotations," had become "an embarrassing term," and should be changed. This article is about the journal For other uses of the term "lancet" see Lancet (disambiguation.  The Lancet supported Down's Syndrome. The World Health Organization (WHO) officially dropped references to mongolism in 1965 after a request by the Mongolian delegate.  However, almost 40 years later, the term ‘mongolism’ still appears in leading medical texts such as Review of Medical Physiology, 22nd Edition, 2005, by Professor William Ganong and General and Systematic Pathology, 4th Edition, 2004, edited by Professor Sir James Underwood. Sir James Cresseé Elphinstone Underwood is an eminent British scientist who was awarded a Knighthood for services to Medicine in the 2005 New Year
In 1975, the United States National Institutes of Health convened a conference to standardize the nomenclature of malformations. "NIH" redirects here For other meanings of NIH see NIH (disambiguation. They recommended eliminating the possessive form: "The possessive use of an eponym should be discontinued, since the author neither had nor owned the disorder. " Although both the possessive and non-possessive forms are used in the general population, Down syndrome is the accepted term among professionals in the USA, Canada and other countries; Down's syndrome is still used in the United Kingdom and other areas. Country to "Dominion of Canada" or "Canadian Federation" or anything else please read the Talk Page The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located 
The Down Syndrome Association of Los Angeles maintains a list of individuals with Down syndrome in roles in TV and movies. 
The Open Directory Project ( ODP) also known as dmoz (from directory "NIH" redirects here For other meanings of NIH see NIH (disambiguation.