The trisomy of chromosome 21 will affect almost every organ system in the body, with a wide range of phenotypic effects, although as mentioned earlier, not all cases of Down syndrome will present with the same phenotype. In all cases of Down syndrome there is a level of cognitive impairment, as well as the characteristic craniofacial features, such as an anteriorly and posteriorly flattened head, dysplastic low-set ears, small nose, depressed nasal bridge, protruding tongue, high-arched palate, dental abnormalities, and a short and broad neck. Further affects of the congenital disorder include, congenital heart disease, skeletal and bone abnormalities, compromised immune systems, hearing defects, increased predisposition to respiratory infections and increased chance of childhood leukemia [7].

Babies born with Down syndrome often have short arms and legs with lower than normal muscle tone, which makes it difficult for them to develop movement. Normal developmental milestones like standing, walking and reaching, often come later than for other children. In addition, 50% of all patients with Down syndrome will have problems with their sight and hearing. Otitis media with effusion is a common problem, which is a build up of fluid in the middle ear that may thicken causing sound to be muffled and distorted. Common eye problems include, a squint or lazy eye, short-sightedness, recurring eye infections and cataracts.

Approximately 1 in 10 patients affected with Down syndrome have issues with their thyroid gland, usually hypothyroidism. Symptoms of an under active thyroid include, lethargy, weight gain and slow reactions, both physical and mental. In more rare cases, Down syndrome patients may be affected with hyperthyroidism, symptoms of which include breathing and sleeping difficulties, and hyperactivity.

• Falling

  Impact on live birth rates may be minimal in settings where termination rates fall. Population-based studies are required to determine the true impact. © 2017 The Authors. Prenatal Diagnosis published by John Wiley & Sons Ltd. [ncbi.nlm.nih.gov]

  Beaver Falls, PA 15010 724-773-6851 Children's Specialty Care Center Erie at Magee–Womens, UPMC Hamot Magee–Womens, UPMC Hamot 118 East 2nd Street W1150 Erie, PA 16507 814-877-8701 Children's Specialty Care Center Hermitage 80 East Silver St., Suite 100 [chp.edu]

  “It looks like he might fall over with every step,” Amy explained earlier that morning on the approach trail. “But somehow it works out 90% of the time.” [climbing.com]

  In the U.S., that percentage falls somewhere between 67 and 90, according to a recent meta-study of Down-syndrome termination rates over the last few decades. [nationalreview.com]

  Researchers from its medical school and the Lucile Packard Children’s Hospital explored why children born with Down syndrome do not start life developmentally delayed but rather fall behind as they get older. [parenting.blogs.nytimes.com]

• Short Stature

  To save this word, you'll need to log in. variants: or Down's syndrome Definition of Down syndrome : a congenital condition characterized especially by developmental delays, usually mild to moderate impairment in cognitive functioning, short stature, [merriam-webster.com]

  Down Syndrome Down Syndrome This photo shows a young man with many typical physical characteristics of Down syndrome such as short stature, frontal balding, thin hair, epicanthal folds, thick neck, and mild truncal obesity. [msdmanuals.com]

  stature, brachycephaly, upslanting palpebral fissures, epicanthus, brushfield spots on the iris, protruding tongue, small ears, short, broad hands, fifth finger clinodactyly, simian crease, and moderate to severe mental retardation The most frequently [icd9data.com]

• Atrial Septal Defect

  The chimpanzee in the present case experienced retarded growth; infantile cataract and vision problems, including nystagmus, strabismus, and keratoconus; congenital atrial septal defect; and hypodontia. [ncbi.nlm.nih.gov]

  About one half of children with Down syndrome are born with heart problems, including atrial septal defect, ventricular septal defect, and endocardial cushion defects. Severe heart problems may lead to early death. [nlm.nih.gov]

• Single Transverse Palmar Crease

  The hands are often short and broad and often have a single transverse palmar crease. The fingers are often short, with clinodactyly (incurving) of the 5th digit, which often has only 2 phalanges. [merckmanuals.com]

  palmar crease, and short fifth finger with clinodactyly. [dx.doi.org]

  transverse palmar creases (~60% of patients) Joint hyperextensibility or hyperflexibility Neuromuscular hypotonia Diastasis recti Dry skin Premature aging Congenital heart defects Complications of Down syndrome can involve almost every organ system of [emedicine.com]

• Fatigue

  The most commonly reported side effects were "diarrhoea, fatigue, insomnia, nausea and vomiting" (page 497; Prasher 2005 ). [doi.org]

  The other five patients positive for IgA-EMAs had gastrointestinal symptoms typical of celiac disease, including bulky stools, failure to thrive, fatigue, and personality changes (Table 1). [journals.lww.com]

  An echocardiogram should be obtained if there is a history of increasing fatigue, shortness of breath, or exertional dyspnea or abnormal physical examination findings, such as a new murmur or gallop. [dx.doi.org]

• Easy Bruising

  Parents of infants with TMD should be counseled regarding the risk of leukemia and made aware of the signs, including easy bruising, petechiae, onset of lethargy, or change in feeding patterns. [dx.doi.org]

• Sleep Apnea

  Significant improvement of parent's complaints (p CONCLUSION: Although adenotonsillectomy improved symptoms and objective sleep data in children with Down syndrome, it was not able to resolve obstructive sleep apnea syndrome in most patients. [ncbi.nlm.nih.gov]

  Prevalence of obstructive sleep apnea in children with Down syndrome. Sleep 2016;39:699-704. Lin SC, Davey MJ. Horne RS. Nixon GM. Screening for obstructive sleep apnea in children with Down syndrome. J Pediatr 2014;165:117-22. [saripediatri.org]

  Refer to a physician with expertise in pediatric sleep any child with signs or symptoms of obstructive sleep apnea or abnormal sleep-study results. Discuss obesity as a risk factor of sleep apnea. [dx.doi.org]

• Delayed Speech Development

  Apart from hearing problems, children with DS have delayed speech development [ 21 ]. Sleep-disordered breathing in children with Down syndrome is seen in half of the children with DS. [doi.org]

• Dyslexia

  It turns out Ally has dyslexia. [theatlantic.com]

  Lisette Hornstra, Eddie Denessen, Joep Bakker, Linda van den Bergh and Marinus Voeten, Teacher Attitudes Toward Dyslexia: Effects on Teacher Expectations and the Academic Achievement of Students With Dyslexia, Journal of Learning Disabilities, 43, 6, [doi.org]

• Seizure

  We hypothesized that the focal seizures in our patient were caused by the PRRT2 mutation, whereas the epileptic spasms were attributable to trisomy 21. [ncbi.nlm.nih.gov]

  Treatments can be given to manage symptoms of either condition, such as seizure medications for a person with cerebral palsy or surgery for heart defects in a child with Down syndrome. [cerebralpalsyguidance.com]

  This leads to an increased risk for memory loss, dementia, late-onset seizures (tonic-clonic seizures in particular), and hypothyroidism. Many individuals will show signs of dementia and develop early-onset Alzheimer's disease by age 40. [emedicinehealth.com]

  […] potential malformations and complications include: short stature, congenital cataract, conductive hearing loss, heart defects (atrio-ventricular canal), digestive malformations (duodenal atresia), Hirschsprung disease, West syndrome (see these terms), seizures [orpha.net]

• Nystagmus

  Nystagmus was related to myopia and esotropia, and to heart disease and heart operations. Conclusions: Comorbidities are common in DS and complicate diagnosis, development, and therapy. [dx.doi.org]

  The chimpanzee in the present case experienced retarded growth; infantile cataract and vision problems, including nystagmus, strabismus, and keratoconus; congenital atrial septal defect; and hypodontia. [ncbi.nlm.nih.gov]

  Ophthalmological disorders Most commonly: Cataracts Refractive errors Strabismus Nystagmus Congenital glaucoma Keratoconus Gastrointestinal disorders Oesophageal atresia or tracheo-oesophageal fistula. Duodenal atresia. Pyloric stenosis. [patient.info]

• Profound Intellectual Disability

  Behavior suggestive of attention-deficit/hyperactivity disorder is often present in childhood, and the incidence of autistic behavior is increased (particularly in children with profound intellectual disability). [merckmanuals.com]

  As a general rule, children and adults functioning in the severe and profound intellectual disability range have very limited spoken language skills. [doi.org]

• Cryptorchidism

  RESULTS: Cryptorchidism was observed in 27.5% of the patients (95CI 15.98-42.96). [ncbi.nlm.nih.gov]

  Among the men, the frequency of hypospadias and cryptorchidism was similar to that of the general population. In both men and women, the ages for the onset and completion of puberty were also normal. [dx.doi.org]

• Failure to Thrive

  The other five patients positive for IgA-EMAs had gastrointestinal symptoms typical of celiac disease, including bulky stools, failure to thrive, fatigue, and personality changes (Table 1). [journals.lww.com]

  If severe or contributing to cardiorespiratory problems or failure to thrive, refer for subspecialty intervention. Stridor, wheezing, or noisy breathing. [dx.doi.org]

  Unsupervised dietary restriction can affect a child’s growth, and bone health, leading to nutritional deficiency and failure to thrive. [indi.ie]

• Abdominal Pain

  METHODS: Computed tomography (CT) images of the pelvis of 42 patients with Down syndrome and hip symptoms were compared with those of 42 age and sex-matched subjects without Down syndrome or history of hip disease who had undergone CT for abdominal pain [ncbi.nlm.nih.gov]

  Signs and symptoms include cramping, abdominal pain, bloating, gas, and diarrhea or constipation, or both. IBS is a chronic condition that you'll need to manage long term. Only a small number of people with IBS have severe signs and symptoms. [mayoclinic.org]

  pain, nausea, diarrhoea, and mild to moderate enlargement of ovaries and ovarian cysts mt Ġurnta fuq il-baħar imma mhux għas-sajd jew waqt transitu en The most common location of cysts is the liver, but cysts may develop in almost any organ, including [glosbe.com]

  The adverse events recorded include nausea, vomiting, dizziness, weight loss, anorexia, abdominal pain, tremor and occurred at were found to be statistically significant levels at higher doses compared to people given placebo. [doi.org]

  For children on a diet that contains gluten, at each preventative care visit review for symptoms potentially related to celiac disease, including diarrhea or protracted constipation, slow growth, unexplained failure to thrive, anemia, abdominal pain or [dx.doi.org]

• Nausea

  A 35-year-old female patient had visited another hospital for 1 month for abdominal discomfort, nausea, constipation, and palpable mass. Cystic mass in the pelvic cavity, increased BUN, and Cr findings were observed. Residual urine was 1.8 L. [ncbi.nlm.nih.gov]

  […] laryngotomies, periosteal stripping, cyst or lump excisions, repair of facial fractures, cast applications and umbilical hernia repairs. mt Pjan ta’ Twaqqif għall en Clinical symptoms and signs of mild ovarian hyperstimulation syndrome are abdominal pain, nausea [glosbe.com]

  The most commonly reported side effects were "diarrhoea, fatigue, insomnia, nausea and vomiting" (page 497; Prasher 2005 ). [doi.org]

• Heart Murmur

  The doctor may hear a heart murmur when listening to the baby's chest with a stethoscope. A blood test can be done to check for the extra chromosome and confirm the diagnosis. [nlm.nih.gov]

  Down Syndrome and Diet-Related Issues Heart Defects: 40-50% of babies with Down Syndrome have congenital heart defects ranging from a heart murmur to more severe conditions requiring cardiac surgery. [indi.ie]

• Macroglossia

  Recent findings Genetic reasons for macroglossia are being identified. Sleep endoscopy and imaging allow assessment of tongue base-induced obstructive sleep apnea. Dental malocclusion and macroglossia are associated. [doi.org]

  In the postnatal period, characteristic phenotypical features point to the diagnosis: depressed nasal bridge epicanthic folds abundant neck skin macroglossia simian crease ( single palmar crease ) hypotonia Intellectual disability becomes evident in early [radiopaedia.org]

  These mid-face problems, together with hypotonia and macroglossia (children with DS have a relatively large tongue compared to the oral cavity), are responsible for chronic middle ear disease and chronic rhinorrhoea. [dx.doi.org]

• High Arched Palate

  palate, dental abnormalities, and a short and broad neck. [symptoma.com]

  Mouth: Protruding tongue (small narrow palate). High arched palate. Neck: Loose skin on nape of neck. Hands: Single palmar crease. Short little finger. In-curved little finger. Short broad hands. Feet: Gap between hallux and second toes. [patient.info]

  In addition, the tongue may appear larger due to a high arched palate, a smaller oral cavity and reduced muscle tone in the tongue. Teeth tend to appear at a later stage. [indi.ie]

• Malocclusion

  Dental malocclusion and macroglossia are associated. Technical modifications to increase macroglossia surgery safety and efficacy have been described. An anatomic and functional basis for tongue reduction surgery is being developed. [doi.org]

  55][57][58][59] Higher rates of tooth wear and bruxism are also common.[57] Other common oral manifestations of Down syndrome include enlarged hypotonic tongue, crusted and hypotonic lips, mouth breathing, narrow palate with crowded teeth, class III malocclusion [en.wikipedia.org]

• Fissured Tongue

  They had upward slanting eyes, flattening of the back of the head and poorly controlled and fissured tongues. [downs-syndrome.org.uk]

• Hearing Problem

  Individuals with Down syndrome are at an increased risk for heart, gastrointestinal, hematologic, respiratory, visual, sensory-motor, speech and language and hearing problems. [genetics.emory.edu]

  They may have hearing problems and problems with the intestines, eyes, thyroid, and skeleton. The chance of having a baby with Down syndrome increases as a woman gets older. Down syndrome cannot be cured. [medlineplus.gov]

  problems, Alzheimer’s disease, childhood leukemia and thyroid conditions. [ndss.org]

  Children with Down syndrome have a higher incidence of infection, respiratory, vision and hearing problems as well as thyroid and other medical conditions. [web.archive.org]

  Up to 75% of children with Down syndrome have problems with their hearing. They need regular hearing screenings and may need to have hearing problems corrected. Vision problems. [familydoctor.org]

• Hearing Impairment

  We report a patient with non-Down syndrome AML, also known as AMKL, with monosomy 7, who was also obese and had a hearing impairment and mental retardation. [ncbi.nlm.nih.gov]

  These have often been based on samples where children with the most severe hearing impairments have been excluded and so results do not generalize to the wider population with Down syndrome. [dx.doi.org]

• Low Set Ears

  Abnormalities are variable from individual to individual and may include mental retardation, retarded growth, flat hypoplastic face with short nose, prominent epicanthic skin folds, small low-set ears with prominent antihelix, fissured and thickened tongue [icd9data.com]

  Some common physical signs of the disorder include a small head, flattened face, short neck, up-slanted eyes, low-set ears, enlarged tongue and lips, and sloping underchin. [britannica.com]

  In all cases of Down syndrome there is a level of cognitive impairment, as well as the characteristic craniofacial features, such as an anteriorly and posteriorly flattened head, dysplastic low-set ears, small nose, depressed nasal bridge, protruding [symptoma.com]

  These features include: upward slanting eyes, flattened bridge of the nose, prominent tongue and low set ears. </p><p>Although children with Down syndrome share some common physical characteristics, they do not all look the same. [aboutkidshealth.ca]

• Short Hands

  […] fold that comes out from the upper eyelid and covers the inner corner of the eye White spots on the colored part of the eye (called Brushfield spots) Wide, short hands with short fingers A single, deep, crease across the palm of the hand A deep groove [nichd.nih.gov]

  Wide, short hands with short fingers White spots on the colored part of the eye (Brushfield spots) Physical development is often slower than normal. [nlm.nih.gov]

  […] tone Broad, short hands with a single crease in the palm Relatively short fingers and small hands and feet Excessive flexibility Tiny white spots on the colored part (iris) of the eye called Brushfield's spots Short height Infants with Down syndrome may [mayoclinic.org]

• Muscle Hypotonia

  These parafunctional activities can be caused by muscle hypotonia and developmental retardation of gross motor function. However, the relationship between the development of gross motor function and oral parafunctional habits remains unclear. [repo.lib.tokushima-u.ac.jp]

  Because of weak, floppy muscles ( hypotonia ), babies learn to sit up, crawl, and walk much later than their normal peers. Talking is also quite delayed. The level of mental retardation is considered to be mild-to-moderate in Down syndrome. [healthofchildren.com]

  Motor control and hypotonia Neonates with DS present with muscle hypotonia and many individuals with DS demonstrate some form of motor impairment, often described as clumsiness or deficits in fine motor control ( Morris et al., 1982 ; Shumway-Cook and [doi.org]

• Dry Skin

  skin, weight gain, and decreased growth velocity relative to the Down’s syndrome growth chart). 16 For the assessment of growth velocity in relation to thyroid function, eight Down’s syndrome children who developed hypothyroidism at the ages of 2–11 [dx.doi.org]

  skin Premature aging Congenital heart defects Complications of Down syndrome can involve almost every organ system of the body. [emedicine.com]

• Eczema

  Alopecia areata (2.9–20%), vitiligo (1.9%), seborrhoeic eczema (8–36%), folliculitis (10.3–26%) and syringoma (12.3–39.2%) are more frequently seen in children with DS. [doi.org]

• Brushfield Spots

  Results: Ocular findings included nystagmus (29.2%), esotropia (26.1%), epiphora (21.5%), Brushfield spots (16.9%), lens opacities (12.3%), abnormalities of the retinal vessels, foveal hypoplasia, or retinal pigment epithelium hyperplasia (32.2%), and [dx.doi.org]

  spots on the iris, protruding tongue, small ears, short, broad hands, fifth finger clinodactyly, simian crease, and moderate to severe mental retardation The most frequently occurring mental retardation/multiple anomaly syndrome usually involving more [icd9data.com]

  Brushfield's spots: Speckled iris. Little white spots that slightly elevated on the surface of the iris arranged in a ring concentric with the pupil. These spots occur in normal children but are far more frequent in Down's syndrome (trisomy 21). [medterms.com]

  […] on the colored part of the eye (called Brushfield spots) Wide, short hands with short fingers A single, deep, crease across the palm of the hand A deep groove between the first and second toes In addition, physical development in children with Down syndrome [nichd.nih.gov]

• Strabismus

  Periocular infection is a rare complication of strabismus surgery. We describe a case of necrotizing Tenon's capsule infection after uncomplicated strabismus surgery in a boy with Down syndrome and blepharitis. [ncbi.nlm.nih.gov]

  Introduction: Ocular problems as refractive errors, strabismus, accommodation, and cataract are well known in children with Down syndrome (DS). [dx.doi.org]

• Almond-Shaped Eyes

  A flattened face — especially across the nose — and upward-slanted, almond-shaped eyes are two of the common physical features of Down syndrome. [everydayhealth.com]

  Individuals with DS may have certain physical attributes including: Almond-shaped eyes with striking Brushfield spots (small, white, crescent-shaped markings) on the irises Single palmar crease on one or both hands Small head or features (such as hands [babycenter.com]

  Some common physical features of Down syndrome include: A flattened face, especially the bridge of the nose Almond-shaped eyes that slant up A short neck Small ears A tongue that tends to stick out of the mouth Tiny white spots on the iris (colored part [cdc.gov]

• Blepharitis

  Patients with Down syndrome may have risk factors for postoperative infection including blepharitis and immunologic abnormalities. [ncbi.nlm.nih.gov]

  […] sightedness- where distant objects appear blurred long sightedness- where nearby objects appear blurred eye infections - most infections occur in either the membrane that covers the eye (conjunctivitis), the middle layer of the eye (uveitis), or the eyelids (blepharitis [hse.ie]

  […] as epicanthal folds, narrowed or slanted palpebral fissures (the mongoloid slant) and Brushfield spots (38–85%)(Fig. 4 ), these vision disorders include strabismus (20–47%), nystagmus (11–29%), congenital cataract (4–7%), acquired cataract (3–15%), blepharitis [doi.org]

• Esotropia

  Nystagmus was related to myopia and esotropia, and to heart disease and heart operations. Conclusions: Comorbidities are common in DS and complicate diagnosis, development, and therapy. [dx.doi.org]

• Short Neck

  Children suffering from Down syndrome show certain features such as flat face, a short neck, slating eyes and small mouth. They also have small degree of intellectual disability. [imedpub.com]

  Symptoms include short head,short neck,poor muscle tone, excessive flexibility etc. Down Syndrome results when each cell in the body possess three copies of chromosome 21 instead of two copies. [longdom.org]

  Some of the other common physical characteristics include a short neck, small hands and feet, small stature, and a lack of muscle tone. [everydayhealth.com]

  stocky arms and legs a wide space between the big toe and second toe short necks and small hands with short fingers one single crease that goes straight across the palm, and a second crease that curves down by the thumb, rather than three creases in [childrenshospital.org]

  Physical Symptoms Common physical signs of Down syndrome include1,2: Decreased or poor muscle tone Short neck, with excess skin at the back of the neck Flattened facial profile and nose Small head, ears, and mouth Upward slanting eyes, often with a skin [nichd.nih.gov]

Antenatal screening for Down syndrome was first developed in the 1970s using previous history of congenital disorders and advanced maternal age. Things moved on in the 1980s when it was discovered that there was an association with Down syndrome and abnormal levels of serum markers, such as alpha fetoprotein and human chorionic gonadotrophin. Maternal serum screening further improved the detection rate of Down syndrome [11].

Recently, the ultrasound has become an extremely useful tool for screening for Down syndrome, which offers a number of advantages. The condition can be detected in the first trimester via fetal nechal translucency thickness; by accurately dating the pregnancy there can be a more precise evaluation or serum screening; and an ultrasound in the second trimester can reveal minor and major structural abnormalities characteristic of the condition [11].

Screening for trisomy at chromosome 21 should be an option for all women as part of their routine antenatal care, being fully informed of the implications and limitations of the screening methods. Women deemed in the high risk group following screening, should then be offered diagnostic testing to determine if their foetus is affected by trisomy 21. Since invasive prenatal diagnosis has around a 1% risk of miscarriage, information gained from the various screening techniques is combined with maternal age to greatly lower the number of false positive rate and therefore reduce the need for unnecessary invasive testing [11].

• Hyperuricemia

  EMBO J 26:3968–3980 PubMed CrossRef Google Scholar Pant SS, Moser HW, Krane SM (1968) Hyperuricemia in Down’s syndrome. [doi.org]

  Decreased buffering of metabolic processes results in a predisposition to hyperuricemia and increased insulin resistance. Diabetes mellitus develops in many affected patients. Premature senescence causes cataracts and Alzheimer disease. [emedicine.com]

• Karyotype Abnormal

  Instead, several karyotypic abnormalities are more frequent in ML-DS than in children without Down syndrome, including trisomy 8, trisomy 11, trisomy 21, del (6q), del(7p), del(16q) and dup(1p) [ 49 ]. [doi.org]

Treatment depends on the organ systems involved.

Over the past 50 years the prognosis of people with Down syndrome has greatly improved, with individuals being healthier, well integrated into society with jobs and social lives, and have improved life expectancies. However, compared to non-Down patients their life expectancy is still reduced. Studies have shown that 1 year survival rates for infants with Down syndrome increased from 60% in the 1940's to over 90% in the 1980s [8]. A study of 389 Down syndrome infants between 1980 and 1989 showed that survival rate were 88% at 1 year and 82% at 10 years. There was a reduced survival rate in patients with congenital heart defects, which was at 72% at 10 years, with pneumonia often being a complication. Information in the cause of death were obtained for 55 of the 63 (87%) deaths, which are as follows:

47.3% caused by cardiac abnormalities.
10.9% caused by leukaemia.
9.1% of deaths were the result of respiratory infection.
3.6% caused by pulmonary hypertension.
14.5% of deaths from other causes.

The life expectancy of those with Down syndrome has greatly improved in the last 100 years. For example in Australia the average life expectancy has gone from 18 years in 1963 to 60 years in 2002 [9]. For those reaching their sixth decade, their longer lifespan is associated with better cognitive functioning [10].

With longer life spans and improved prognosis, patients with Down syndrome can now live a relatively long and fulfilled life. With medical management, early intervention, an appropriate home environment, education and vocational training, the cognitive level of functioning of Down syndrome children and adolescents is improved, greatly helping with the transition into adulthood12. Patients should be actively encouraged to develop a level of independence and participate in recreational and social activities.

Down Syndrome is caused by one of three chromosomal anomalies. The majority of cases, around 88%, is caused by full trisomy at chromosome 21. Chromosomal translocation is the cause in approximately 4.5% of cases, with the remaining 7.5% of cases being the result of mosaic trisomy [6].

In approximately 79.5% of cases the chromosomal abnormality is maternal and the remaining 20.5% is paternal [6]. The abnormality is most likely to occur during the first meiotic division, occurring 3 times as often than meiosis II errors.

Many studies have been conducted over the last century to determine the prevalence of Down syndrome, due to its clinical significance. In the most general terms it is estimated that Down syndrome occurs in 1 of 732 births in the United States, although this may vary with maternal age and different ethnic groups [3].

Some evidence has suggested that there is an increased prevalence of Down syndrome in infants of Hispanic mothers when compared to non-Hispanic white mothers and African American or African mothers [4]. However, it is important to note that these variations in prevalence could be influenced by factors affecting the level of healthcare, such as prenatal care and diagnosis, or selective termination [3].

The age of the mother can also affect the prevalence of Down Syndrome, in fact the most important risk factor for Down syndrome is advanced maternal age [3]. There is no significant affect on parental age until it reaches 35 years or older and the risk is at its greatest when the maternal age is 40 years or older [5].

Animal models have proved extremely useful in determining a genetic model for Down syndrome. A popular hypotheses for the abnormal gene mechanism is the gene-dosage hypothesis, where having three copies of the same gene expressed, results in the phenotypes of Down syndrome [2]. It can be explained as a threshold effect – the amount of protein produced from the transcription of the three alleles, has to reach a certain level before the phenotype manifests. If the threshold is not reached then the associate phenotype does not present. This helps to explain why some Down syndrome patients have different phenotypes to others [2].

There are no guidelines for prevention of Down Syndrome.

The most common and well known chromosomal disorder in humans, Down syndrome, is caused by a trisomy at Chromosome 21 [1]. It is a major cause of mental retardation and congenital heart disease and is characterised by dysmorphic body and facial features, problems with the endocrine, immune and digestive systems, as well as an increased risk of developing dementia and leukemia [1].

However, it is important to note that the phenotypic expression of Down syndrome is not the same in each patient, for example there is a congenital heart defect in only 40% of Down syndrome patients [2].

Down syndrome is the result of an extra chromosome 21 i.e. three chromosomes instead of the usual two. The biggest risk factor is an advanced age of the mother, with those over 40 having the highest risk of having a child affected with Down syndrome. In general the condition occurs in approximately 1 in 750 births and can be detected by a number of antenatal screening methods, including ultrasound and maternal blood serum analysis.

The extra chromosome 21 affects every organ system in the body and is characterised primarily with mental retardation and recognisable facial features. Not all cases of Down syndrome are the same, some patients will have different presentations to others. Other affects of the extra chromosomes include, heart disease, skeletal abnormalities, problems with the immune system, hearing difficulties and an increased chance of developing a childhood leukaemia.

Over the past 50 years the prognosis in those with Down syndrome has greatly improved, with it not being unusual for a patient to live into their sixth decade.

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12. Bull M J. Health supervision for children with Down syndrome. Pediatrics 2011 Vol 128(2): 393-406