Down's Syndrome - Causes, symptoms & diagnosis

What is Down syndrome?

Down syndrome (sometimes called Down’s syndrome) is a condition in which a child is born with an extra copy of their 21st chromosome — hence it lead to trisomy 21 this causes physical and mental developmental delays and disabilities.

Many of the disabilities are lifelong, and they can also shorten life expectancy, people with Down syndrome can live healthy and fulfilling lives by taking support from their families, and others cultural institutions provides many opportunities to help overcome the challenges of this condition.

What causes Down syndrome?

When the baby’s cells develop, each cell is supposed to receive 23 pairs of chromosomes, for 46 chromosomes total. chromosomes are received equally from the mother, and from the father.

In children with this syndrome, one of the chromosomes doesn’t separate properly, so the baby ends up with three copies, or an extra partial copy, of chromosome 21, instead of two. The extra chromosome causes problems as the brain and physical features develop. 

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 which is the most common form of Down syndrome.

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

Translocation - In this type 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.

Other parents who are more likely to have a child with Down syndrome include:

  • Children with a family history of Down syndrome

  • people who carry the genetic translocation

  • It’s important to remember that no one of these factors mean that you’ll definitely have a baby with Down syndrome. However, statistically and over a large population, they may increase the chance that you may.

What are the symptoms of Down syndrome?

Though the likelihood of carrying a baby with Down syndrome can be estimated by screening during pregnancy, they may not experience any symptoms of carrying a child with Down syndrome.

At birth, infant with Down syndrome usually have certain signs, that includes:

  • flat facial features

  • small head and ears

  • short neck

  • bulging tongue

  • eyes that slant upward

  • atypically shaped ears

  • poor muscle tone

  • A newborn with Down syndrome can be of average size, but will develop more slowly than a normal child.

People with Down syndrome usually have less degree of developmental disability, but it’s often mild to moderate. Mental and social development delays may occur in the child along with:

  • impulsive behavior

  • poor judgment

  • short attention span

  • slow learning capabilities

Medical complications often accompany Down syndrome, that includes:

  • congenital heart defects

  • hearing loss

  • poor vision

  • cataracts (clouded eyes)

  • hip problems, such as dislocations

  • leukemia

  • chronic constipation

  • sleep apnea (interrupted breathing during sleep)

  • dementia (thought and memory problems)

  • hypothyroidism (low thyroid function)

  • obesity

  • late tooth growth, causing problems with chewing

  • Alzheimer’s disease later in life

People with Down syndrome are also more likely to get infections, which mainly includes respiratory infections, urinary tract infections, and skin infections.

Down's syndrome - screening and diagnosis tests:

Diagnosis is done at various stages of pregnancy of the woman, that includes first trimester, second trimester & other prenatal tests.

First trimester 

 Blood tests and ultrasound evaluation can be used to find for Down syndrome infetus. If results aren't normal, doctor may recommend for Amniocentesis after 15th week of pregnancy.

Second trimester 

Ultrasound and quadruple marker screen (QMS) test can be used to detect Down syndrome and other defects in the brain and spinal cord, which are usually done between 15th to 20th week of pregnancy.

Additional prenatal tests:

These mainly include 

  • Amniocentesis,

  • Chorionic villus sampling (CVS),

  • Percutaneous umbilical blood sampling (PUBS, or cordocentesis).

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