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Understanding Down Syndrome: Causes, symptoms, diagnosis, & treatment

Dr. Rashmi ByakodiNov 28, 2022

Human body cells are made up of tiny structures known as chromosomes. Chromosomes carry the DNA and transfer the genetic codes from parents to their offspring. These DNA genetic codes decide the physical features such as eye colour, hair colour, height, and other natural traits. There are 23 pairs of chromosomes in each cell of the human body, including one pair of sex chromosomes. Down Syndrome, a genetic disorder, occurs when a human child is born with an extra copy of the 21st chromosome.

Babies born with Down Syndrome can have physical and mental disabilities. They may have typical facial and body features like short stature, a flat nasal bridge, low muscle tone, and a protruding tongue that set them apart from the general group. Their development may happen slower than normal, and they may be born with some grave medical conditions like congenital cardiac defects, gastrointestinal tract abnormalities, haematological, neurological, endocrinological, and musculoskeletal disorders, as well as visual and hearing disabilities. Read on to know more about Down Syndrome, its causes, symptoms, and treatment.

Down Syndrome

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What causes Down Syndrome?

Many factors contribute to Down Syndrome, but the principal one is the mother's age. The prevalence of Down Syndrome is higher if a woman becomes pregnant after age 35. There is a 1 in 1,250 chance of conceiving a baby with Down Syndrome at the age of 25. Whereas, at the age of 40 the occurrence becomes around 1 in 100.

At the time of conception, a pair of chromosomes 21 does not separate, and the embryo ends up having three copies or an extra partial copy of chromosome 21 instead of two. As the embryo grows, the extra chromosome is cloned in every cell of the body. As a result, every cell produces an excess of chemicals controlled by chromosome 21. This chemical imbalance causes complications in the mental and physical features as the baby grows up. Other causes of Down Syndrome may include family history and genetic translocation.

Types of Down Syndrome

There are three types of Down Syndrome.

1. Trisomy 21

Trisomy means having an additional copy of the chromosome. In this case, during the time of conception, a pair of chromosome 21 fails to separate in the embryonic cells and ends up having three copies instead of two. Hence, as the foetus grows, the extra chromosome is replicated in each cell of the body, which forms a complete trisomy. Being the most common type of Down Syndrome, trisomy 21 makes up to 95% of the total cases.

2. Mosaicism

It is a type of Down Syndrome, in which most of the body cells have the extra chromosome but some of them do not. Mosaicism can happen when the error in cell division occurs after a normal egg and sperm unite. It can also happen during early development when some cells lose the extra chromosome 21, which was present earlier at the time of conception. Being the rarest type of Down Syndrome, mosaicism symptoms may vary depending on how many cells lose the extra chromosome.

3. Translocation

It is a type of Down Syndrome in which an extra copy of chromosome 21 gets stuck to another chromosome and transferred into other cells as they divide. It is a rare type of Down Syndrome that accounts for 4% of the cases.

Symptoms of Down Syndrome

At birth, kids with Down Syndrome generally have specific physical features, certain developmental disabilities, and unique health problems. Physical features of babies with Down Syndrome include the following.

  • Upward slanting eyes

  • Short stature with a short neck

  • Small ears and head

  • White spot on the iris

  • Flat facial features with flat nasal bridge

  • Smaller limbs

  • Protruding tongue

  • Weak muscle mass

  • Palmar crease (single crease on the palms of the hands)

Other than distinct physical features, babies with Down Syndrome can also have certain developmental disabilities that may include the following.

  • Speech delay

  • Delay in language development

  • Attention issues

  • Sleep disorders

  • Slow learning capacity

  • Tantrums and stubbornness 

  • Cognitive delay

  • Impulsive behaviour

  • Unable to make proper judgement

Medical conditions associated with Down Syndrome

Individuals with Down Syndrome frequently get affected by several medical conditions. Either the health issues are present at birth or may develop over time. Common health conditions associated with Down Syndrome may include the following.

  • Congenital heart disease

  • Thyroid disorder especially hypothyroidism

  • Poor vision and hearing loss

  • Low fertility rate

  • Sleep apnea (a serious sleep disorder with repeated start-stop breathing)

  • Gastroesophageal reflux disease, constipation, and celiac disease (gluten intolerance)

  • Leukaemia

  • Obesity

  • Alzheimer’s disease, and dementia

  • Autism 

Additionally, people with Down Syndrome are also susceptible to infections. They often get infected by skin infections, respiratory tract infections, throat infections, and urinary tract infections.

Diagnosing Down Syndrome

Your healthcare provider can diagnose Down Syndrome by performing the following tests during pregnancy or at birth.

  • Prenatal tests: Your doctor will perform prenatal (before birth) tests such as screenings, blood tests, and ultrasound tests to look for “Down Syndrome markers.”

  • Chorionic villus sampling (CVS): Between 9 to 11 weeks, your doctor takes cell samples from your placenta to study foetal chromosomes.

  • Amniocentesis: During 14th to 18th week, your doctor will take a sample of amniotic fluid to study the number of chromosomes in each cell your baby carries.

  • Percutaneous umbilical blood sampling (PUBS) or cordocentesis: After 20 weeks, blood samples from your umbilical cord will be taken by your doctor to examine the chromosomal defects. Since the risk of miscarriage is high in this test, it is done only when other tests are uncertain.

  • Test at birth: Your doctor will look for physical characteristics of Down Syndrome at birth. If required, a blood test called a karyotype is done to ensure the diagnosis. In this test a blood sample is examined under a microscope to understand if any extra chromosome 21 is present. 

How is Down Syndrome treated?

The treatment for Down Syndrome starts in early childhood. This can help your child learn to cope with the condition and tackle the physical and cognitive challenges. Your doctor may provide you with a team of specialists in different fields. The team of specialists may include the following.

  • Primary care providers to observe development, growth, and vaccinations

  • Team of physicians depending on the health needs of your child such as cardiologist, ENT specialist, endocrinologist, etc.

  • Speech therapists to help your child learn communication

  • Physiotherapists to help strengthen your child’s muscles

  • Occupational therapists to help improve the motor skills of your child

  • Behavioural therapists to help your child handle emotional challenges

Frequently Asked Questions

Here’s a list of common questions and answers related to Down Syndrome.

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Is it possible to prevent Down Syndrome?

Unfortunately, there is no way to prevent Down Syndrome. However, if you give birth before age 35, you can lower your chances of having a child with Down Syndrome.

How can Down Syndrome be managed?

With the right treatment and therapies, Down Syndrome can be managed. With appropriate medical aid and different therapies like speech, occupational, and behavioural therapies with physiotherapy, you can help your child lead a healthy and active life.

Why is Down Syndrome caused?

Down Syndrome is caused when, during the time of conception, a pair of chromosome 21 fails to separate in the embryonic cells and ends up having three copies of chromosome 21 instead of two. Hence, as the foetus grows, the extra chromosome is replicated in each cell of the body, and every cell produces an extra amount of chemicals regulated by chromosome 21. This chemical imbalance causes complications in the mental and physical features as the baby grows up.

What factor carries the highest risk of developing Down Syndrome?

The possibility of Down Syndrome is higher if a woman becomes pregnant after the age of 35. There is a 1 in 1,250 chance of conceiving a baby with Down Syndrome at the age of 25. Whereas at the age of 40 the occurrence becomes around 1 in 100.

Sources

Disclaimer: The content on this page is generic and shared only for informational and explanatory purposes. Please consult a doctor before making any health-related decisions.

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