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Down Syndrome

Langdon Down Syndrome

Down syndrome is the most common and best known chromosomal disorder in humans. It is typically associated with mental retardation, developmental delays and a particular set of facial characteristics. The three genetic variations that can cause Down syndrome include: Trisomy 21, mosaic Down syndrome and translocation Down syndrome.


Presentation

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.

Atrial Septal Defect
  • Additional external findings included alopecia universalis, penoscrotal hypospadias, ostium secundum type of atrial septal defect, right ventricular cardiac dilatation, diffuse cerebral atrophy, facial features compatible with Down syndrome, and generalized[ncbi.nlm.nih.gov]
  • Whether aIMT differs according to the type of congenital heart defect (such as atrial septal defect, ventricular septal defect, patent ductus arteriosus, and atrioventricular septal defect) among DS patients remains to be determined in future studies.[ncbi.nlm.nih.gov]
  • Ventricular septal defect, atrioventricular septal defect and atrial septal defect were the most frequent isolated defects. There was a downward trend in the prevalence of overall CHD (from 56.2% to 25.0%) and isolated CHD (from 56.2% to 19.8%).[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]
Short Stature
  • […] 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, upward slanting eyes, a flattened nasal bridge[merriam-webster.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]
  • Short stature as the major manifestation of celiac disease in older children. Clin Pediatr 1986; 25:13–6. 12. Rossi TM, Kumar V, Lerner A, et al.[journals.lww.com]
  • The main 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[orpha.net]
  • The characteristics of Down syndrome include low muscle tone, short stature, a flat nasal bridge, and a protruding tongue. People with Down syndrome have a higher risk of some conditions, including Alzheimer's disease and epilepsy.[medicalnewstoday.com]
Single Transverse Palmar Crease
  • palmar crease, and short fifth finger with clinodactyly.[dx.doi.org]
  • palmar crease, and short fifth finger with clinodactyly and wide spacing, often with a deep plantar groove between the first and second toes.[dx.doi.org]
Sleep Apnea
  • OBJECTIVES: To evaluate the evolution of polysomnographic parameters of children with Down syndrome and obstructive sleep apnea syndrome submitted to adenotonsillectomy and the interaction of comorbidities on therapeutic outcome.[ncbi.nlm.nih.gov]
  • Kristen's presentation was exacerbated by salient environmental stress and sleep apnea, rather than a cognitive regression associated with a medical cause.[ncbi.nlm.nih.gov]
  • It is an effective treatment of sleep apnea in select adult patients because it allows for alleviation of tongue base collapse, improving airway obstruction.[ncbi.nlm.nih.gov]
  • OBJECTIVE: Evaluate peri-operative course and morbidity in children with Down syndrome (DS) who underwent a lingual tonsillectomy (LT) for residual obstructive sleep apnea (rOSA).[ncbi.nlm.nih.gov]
  • This review provides an overview of the various causes of respiratory disease, and insight into some of the newer therapies available to treat obstructive sleep apnea, in this population. Copyright 2017 Elsevier Ltd. All rights reserved.[ncbi.nlm.nih.gov]
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.[ncbi.nlm.nih.gov]
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]
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.[ncbi.nlm.nih.gov]
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]
  • [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]
  • Katsaris , Malocclusion and the need for orthodontic treatment in 8‐year‐old children with Down syndrome: a cross‐sectional population‐based study , Special Care in Dentistry , 36 , 4 , (194-200) , (2016) .[doi.org]
High Arched 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. Congenital heart defects. Duodenal atresia.[patient.info]
  • palate, dental abnormalities, and a short and broad neck.[symptoma.com]
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]
  • If appropriate, discuss skin problems: very dry skin and other skin problems are particularly common in patients with Down syndrome. Discuss symptoms related to obstructive sleep apnea, including snoring, restless sleep, and sleep position.[dx.doi.org]
  • Very dry skin, which may be a sign of hypothyroidism, and other skin problems are particularly common in patients with Down syndrome. Therefore, be attentive to these dermatologic problems and discuss them with the patient and family.[dx.doi.org]
Hearing Problem
  • 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]
  • 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]
  • These could include heart disease, hearing problems, or problems with their intestines. Many begin treatment for medical issues early and live full, healthy, productive lives.[familydoctor.org]
  • problems, probably caused by repeated ear infections Hip problems and risk of dislocation Long-term (chronic) constipation problems Sleep apnea (because the mouth, throat, and airway are narrowed in children with Down syndrome) Teeth that appear later[nlm.nih.gov]
Hearing Impairment
  • Abstract 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]
  • The management of significant co-morbidities in children with DS can delay initial diagnosis of hearing impairment and assessment of suitability for CI can likewise be challenging, due to difficulties conditioning to behavioural hearing tests.[ncbi.nlm.nih.gov]
  • We provide data on thyroid disease, cervical spine disease, hearing impairment, overweight-obesity, sleep apnea, congenital heart disease, and osteopenia-osteoporosis.[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]
  • impairment Inwardly curved little finger Abnormal space between the great and second toe Unusual creases on the soles of the feet and one or both hands Tests to confirm Down syndrome are often done before a baby is born through amniocentesis or chorionic[chop.edu]
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]
  • 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]
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]
  • spots) Physical development is often slower than normal.[nlm.nih.gov]
Epicanthal Folds
  • In 1876 he specifically identified the fold of skin at the inner corner of the eyes which he described as epicanthic folds and he also noted that the ear was usually placed further back in relation to the head and face than in normal children.[intellectualdisability.info]
  • 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]
  • Epicanthic folds. Ring of iris speckles - Brushfield's spots. Ears set low, folded or stenotic meatus. Flat nasal bridge. Mouth: Protruding tongue (small narrow palate). High arched palate. Neck: Loose skin on nape of neck.[patient.info]
Almond-Shaped Eyes
  • 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]
  • 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]
Blepharitis
  • We describe a case of necrotizing Tenon's capsule infection after uncomplicated strabismus surgery in a boy with Down syndrome and blepharitis. Pathologic diagnosis was severe acute necrotizing inflammation with Gram positive coccal forms.[ncbi.nlm.nih.gov]
  • […] 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[ncbi.nlm.nih.gov]
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 Hands
  • 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]
  • 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 be average size[mayoclinic.org]
Muscle Hypotonia
  • For example, most individuals with DS have memory and learning difficulties, craniofacial alterations and muscle hypotonia, but only some have congenital heart malformations, leukaemia or gut abnormalities.[doi.org]
  • 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]
  • The disorder can be diagnosed in utero by screening or karotyping, or early after birth by muscle hypotonia (poor muscle tone) and other symptoms and confirmed by karyotype analysis of a blood sample ( Saenz 1999 ).[doi.org]
Short Neck
  • 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]
  • Though not all people with Down syndrome have the same features, some of the more common features include: Flattened face Small head Short neck Protruding tongue Upward slanting eye lids (palpebral fissures) Unusually shaped or small ears Poor muscle[mayoclinic.org]
  • At birth, babies with Down syndrome usually have certain characteristic signs, including: flat facial features small head and ears short neck bulging tongue eyes that slant upward atypically shaped ears poor muscle tone An infant with Down syndrome can[healthline.com]
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]
Seizure
  • She had focal seizures at five months of age, which were controlled with phenobarbital. However, epileptic spasms appeared at seven months of age in association with hypsarrhythmia.[ncbi.nlm.nih.gov]
  • The evaluation in the DS clinic focused on potential medical diagnoses including atlantoaxial joint instability, vitamin deficiency, obstructive sleep apnea (OSA), and seizures.[ncbi.nlm.nih.gov]
  • […] 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]
  • 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]
  • Seizures occur in 5-10%. In older patients an Alzheimer's-type picture develops in 60% of those over 60 years of age.[patient.info]
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]
  • 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]
  • Check for strabismus, cataracts, and nystagmus by 6 months, if not done at birth. Check the infant's vision at each visit, using developmentally appropriate subjective and objective criteria.[dx.doi.org]
  • In addition to ocular features related to DS such 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[ncbi.nlm.nih.gov]

Workup

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].

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

Treatment depends on the organ systems involved.

Prognosis

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.

Etiology

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.

Epidemiology

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].

Sex distribution
Age distribution

Pathophysiology

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].

Prevention

There are no guidelines for prevention of Down Syndrome.

Summary

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].

Patient Information

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.

References

Article

  1. Korenberg JR, Chen XN, Schipper R, et al. Down Syndrome phenotypes: The consequences of chromosomal imbalance. Proc. Natl. Acad. Sci. 1994 Vol 91: 4997-5001.
  2. Antonarakis AE, Lyle R, Dermizakis ET, et al. Chromosome 21 and Down syndrome: From genomics to pathophysiology. Nature Reviews. 2004 Vol 5: 725-738
  3. Sherman SL, Allen EG, Bean LH, Freeman SB. Epidemiology of Down syndrome. Mental Retardation and Developmental Disabilities 2007 Vol 13: 221-227
  4. Canfield MA, Honein MA, Yuskiv N. et al. National estimates and race/ethnic-specific variation of selected birth defects in the United States, 1999-2001. Birth Defects Res A Clin Mol Teratol. 2006 Vol 76(11): 747-56
  5. Fisch H, Hyun G, Golden R et al. The influence of paternal age on Down syndrome. The Journal of Urology. 2003 Vol 169: 2275-2278
  6. Jyothy A, Kumar KSD, Naga G, et al. Parental age and the origin of extra chromosome 21 in Down syndrome. J Hum Genet. 2001 Vol 46: 347-350
  7. Kola I, Hertzog PJ. Animal models in the study of the biological function of genes on human chromosome 21 and their role in the pathophysiology of Down syndrome. Human Molecular Genetics 1997 Vol 6(10):1712-1727
  8. Johnson CHZ, Thornton L, Fogarty J, et al. Ten-year survival of Down syndrome births. International Journal of Epidemiology. 1997 Vol 6(4): 822-829
  9. Bittles AH, Glasson E J. Clinical, social and ethical complications of changing life expectancy in Down syndrome. Developmental Medicine and Child Neurology. 2004 Vol 46(4): 282-286
  10. Coppus AM, Evenhuis HM, Verberne GJ, et al. Survival in elderly persons with Down syndrome. J Am Geriatr Soc. 2008 Vol 56(12):2311-6.
  11. Khalil A, Pandya P. Screening for Down syndrome. J Obstet Gynecol India 2006 Vol 56(3): 205-211
  12. Bull M J. Health supervision for children with Down syndrome. Pediatrics 2011 Vol 128(2): 393-406

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Last updated: 2018-06-22 12:28