INTRODUCTION:

Down syndrome was first described by an English physician John Langdon Down in 1866, but its association with chromosome 21 was established almost 100 years later by Dr. Jerome Lejeune in Paris. It is the presence of all or part of the third copy of chromosome 21 which causes Down syndrome, the most common chromosomal abnormality occurring in humans. It is also found that the most frequently occurring live born aneuploidy is trisomy 21 that causes this syndrome.¹

Down syndrome is one of the most common chromosome abnormalities in humans. It occurs in about 1 in 1,000 babies born each year. In 2015, Down syndrome was present in 5.4 million individuals globally and resulted in 27,000 deaths, down from 43,000 deaths in 1990. Some aspects of the condition were described earlier by French psychiatrist Jean-Étienne Dominique Esquirol in 1838 and French physician ÉdouardSéguin in 1844.The genetic cause of Down syndrome was discovered in 1959.²

Down syndrome is one of the most leading causes of intellectual disability and millions of these patients face various health issues including learning and memory, congenital heart diseases(CHD), Alzheimer’s diseases (AD), leukemia, cancers and Hirschprungdisease(HD). The incidence of trisomy is influenced by maternal age and differs in population (between 1 in 319 and 1 in 1000 live births). DS has high genetic complexity and phenotype variability. In developed countries, the average life span for DS population is 55 years using a series of screenings and tests, healthcare professionals can detect Down syndrome before or after birth.Down syndrome occurs in around 1 in every 700 pregnancies. It is determined by many factors, but research suggests that there is a higher chance if the mother is older than 35 years of age.Before the age of 30, Down syndrome occurs in less than 1 in 1,000 pregnancies. After the age of 40, this figure rises to about 12 in 1,000.³

What is Down syndrome?

It is a genetic condition that occurs when there is an extra copy of a specific chromosome: chromosome 21. Down syndrome is not an illness. The term describes the features resulting from this change. The extra chromosome can affect a person’s physical features, intellect, and overall development. It also increases the likelihood of some health problems.

Causes:

All cells in the body contain genes that are grouped along chromosomes in the cell nucleus. There are normally 46 chromosomes in each cell 23 inherited from the mother and 23 from the father.When some or all of a person’s cells have an extra full or partial copy of chromosome 21, down syndrome occurs.⁴

Types of Down syndrome:

There are three types of Down syndrome:

Trisomy 21: Trisomy 21 means there’s an extra copy of chromosome 21 in every cell. This is the most common form of Down syndrome.

Mosaicism: Mosaicism occurs when a child is born with an extra chromosome in some but not all of their cells. People with mosaic Down syndrome tend to have fewer symptoms than those with trisomy 21.

Translocation: In this type of Down syndrome, children have only an extra part of chromosome 21. There are 46 total chromosomes. However, one of them has an extra piece of chromosome 21 attached.⁵

Symptoms:

Each person with Down syndrome is an individual intellectual and developmental problems may be mild, moderate or severe. Some people are healthy while others have significant health problems such as serious heart defects.Children and adults with Down syndrome have distinct facial features. Though not all people with Down syndrome have the same features, some of the more common features include:

Characteristics	%	Characteristics	%
Mental impairment	99%	Abnormal teeth	60%
Stunted growth	90%	Slanted eyes	60%
Umbilical hernia	90%	Shortened hands	60%
Increased skin on back of neck	80%	Short neck	60%
Low muscle tone	80%	Obstructive sleep apnea	60%
Narrow roof of mouth	76%	Bent fifth finger tip	57%
Flat head	75%	Brushfield spots in the iris	56%^]
Flexible ligaments	75%	Single transverse palmar crease	53%
Proportionally large tongue	75%	Protruding tongue	47%
Abnormal outer ears	70%	Congenital heart disease	40%
Flattened nose	68%	Strabismus	~35%

· Flattened face

· Small head

· Short neck

· Protruding tongue

· Upward slanting eye lids (palpebral fissures)

· Unusually shaped or small ears

· Poor muscle 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 be average size, but typically they grow slowly and remain shorter than other children the same age.

Intellectual disabilities:

Most children with Down syndrome have mild to moderate cognitive impairment. Language is delayed, and both short and long-term memory is affected.⁶

Prenatal Screening and Diagnosis:

Two types of prenatal tests are used to detect Down syndrome in a fetus: screening tests and diagnostic tests. Screening tests estimate the risk that a fetus has DS; diagnostic tests can tell whether the fetus actually has the condition.

Screening tests include:

Nuchal translucency testing:

This test, performed between 11 and 14 weeks of pregnancy, uses ultrasound to measure the clear space in the folds of tissue behind a developing baby's neck. Nuchal translucency testing is usually performed along with a maternal blood test.

The triple screen or quadruple screen (also called the multiple marker test):

These tests measure the quantities of normal substances in the mother's blood. These tests are typically offered between 15 and 18 weeks of pregnancy.

· Integrated screen: This uses results from first-trimester screening tests (with or without nuchal translucency) and blood tests with a second trimester quadruple screen to come up with the most accurate screening results.

· A genetic ultrasound: A detailed ultrasound is often performed at 18 to 20 weeks in conjunction with the blood tests, and it checks the fetus for some of the physical traits abnormalities associated with Down syndrome.

· Cell free DNA: This test analyzes fetal DNA found in the mother’s blood. It can be done in the 1st trimester and is more accurate at detecting Trisomy 21 than standard blood tests. Currently cell free DNA testing is only offered to women at high risk of having a baby with Down syndrome.

Diagnostic tests include:

Chorionic villus sampling (CVS):

CVS involves taking a tiny sample of the placenta, either through the cervix or through a needle inserted in the abdomen.

Amniocentesis:

This test, performed between 15 and 20 weeks of pregnancy, involves the removal of a small amount of amniotic fluid through a needle inserted in the abdomen. The cells can then be analyzed for the presence of chromosomal abnormalities.

Percutaneous umbilical blood sampling (PUBS) or cordocentesis:

Usually performed after 18 weeks, this test uses a needle to retrieve a small sample of blood from the umbilical cord.

After a baby is born, if the doctor suspects DS based on the infant's physical characteristics, a karyotypea blood or tissue sample stained to show chromosomes grouped by size, number, and shape can be done to verify the diagnosis.⁷

Treatment:

There is no single, standard or specific treatment for Down syndrome. Treatment for Down syndrome varies. It typically starts in early childhood. The purpose is for you and your child with Down syndrome to learn to cope with the condition, as well as treat what physical and cognitive (thinking) challenges arise. Your providers may help you develop a care team for your family member with Down syndrome. The care team may include:

1. Primary care providers to monitor growth, development, medical concerns and provide vaccinations.

2. Medical specialists depending on the needs of the person (for example, cardiologist, endocrinologist, geneticist, hearing and eye specialists).

3. Speech therapists to help them communicate.

4. Physical therapists to help strengthen their muscles and improve motor skills.

5. Occupational therapists to help refine their motor skills and make daily tasks easier. May require evaluation and care, sometimes requiring surgery.

6. Behavioral therapists to help manage emotional challenges that can come with Down syndrome.

Prevention:

Down syndrome can’t be prevented, but parents can take steps that may reduce the risk. The older the mother, the higher the risk of having a baby with Down syndrome. Women can reduce the risk of Down syndrome by giving birth before age 35.⁸

Complications:

People with Down syndrome can have a variety of complications, some of which become more prominent as they get older. These complications can include:

· Heart defects: About half the children with Down syndrome are born with some type of congenital heart defect. These heart problems can be life-threatening and may require surgery in early infancy.

· Gastrointestinal (GI) defects: GI abnormalities occur in some children with Down syndrome and may include abnormalities of the intestines, esophagus, trachea and anus. The risk of developing digestive problems, such as GI blockage, heartburn (gastroesophageal reflux) or celiac disease, may be increased.

· Immune disorders: Because of abnormalities in their immune systems, people with Down syndrome are at increased risk of developing autoimmune disorders, some forms of cancer, and infectious diseases, such as pneumonia.

· Sleep apnea: Because of soft tissue and skeletal changes that lead to the obstruction of their airways, children and adults with Down syndrome are at greater risk of obstructive sleep apnea.

· Obesity: People with Down syndrome have a greater tendency to be obese compared with the general population.

· Spinal problems: Some people with Down syndrome may have a misalignment of the top two vertebrae in the neck (atlantoaxial instability). This condition puts them at risk of serious injury to the spinal cord from overextension of the neck.

· Leukemia: Young children with Down syndrome have an increased risk of leukemia.

· Dementia: People with Down syndrome have a greatly increased risk of dementia-signs and symptoms may begin around age 50. Having Down syndrome also increases the risk of developing Alzheimer's disease.

· Other problems: Down syndrome may also be associated with other health conditions, including endocrine problems, dental problems, seizures, ear infections, and hearing and vision problems.⁹

CONFLICT ON INTEREST:

Nil

REFERENCES:

1. Wahab AA, Bener A, Teebi AS. The incidence patterns of Down syndrome in Qatar. Clin Genet. 2006; 69: 360-2.

2. Bull MJ, the Committee on Genetics. Health supervision for children with Down syndrome. Pediatrics. 2011; 128: 393-406.

3. https://en.wikipedia.org/wiki/Down_syndrome

4. Ambreen A., Kumar A.; Down syndrome: an insight of the disease. Journal of Biomedical Science. 2015; 22(41): 1-26.

5. Crosta P. what to know about Down syndrome; Medical News Today. Dec. 2017; 4(3): 24-30.

6. Amiel J, Sproat-Emison E, Garcia-Barcelo M, Lantieri F, Burzynski G, Borrego S, et al. Hirschsprung disease, associated syndromes and genetics: a review. J Med Genet. 2008; 45: 1-14.

7. Charles M.Down syndrome, Mayo Clinic Family Health Book; 5th Ed.dec.2018: 35-40.

8. Mary L. Gavin, MD Down syndrome; Kids Health. Sep. 2015; 3(2): 1-7.

9. Salehi A, Delcroix JD, Belichenko PV, Zhan KWC, Valletta JS, Takimoto-Kimura, et al. Increased App expression in a mouse model of Down’s syndrome disrupts NGF transport and causes cholinergic neuron degeneration. Neuron. 2006; 51: 29-42.

10. Lwerence k.Down syndrome, Mayo Clinic Family Health Book. 5th Ed.dec.2018; 3(4): 35-40.

Received on 26.04.2021 Modified on 10.05.2021

Int. J. of Advances in Nur. Management. 2021; 9(3):328-331.

DOI: 10.52711/2454-2652.2021.00075

Symptoms:

Intellectual disabilities:

Most children with Down syndrome have mild to moderate cognitive impairment. Language is delayed, and both short and long-term memory is affected.6

Prenatal Screening and Diagnosis:

Treatment:

Most children with Down syndrome have mild to moderate cognitive impairment. Language is delayed, and both short and long-term memory is affected.⁶