What is Down Syndrome? Symptoms, Types, Diagnosis and Treatment Methods

Down syndrome is a genetic difference that develops as a result of a person being born with an extra chromosome. This genetic difference, which has 3 different types including Trisomy 21, translocation Down syndrome, and mosaic Down syndrome, can manifest with different symptoms depending on the type. Although there is no definitive cure for Down syndrome today, various treatment methods applied in the early period can contribute to the individual's physical and mental development.

What is Down Syndrome?

Down syndrome is a genetic difference in which a person is born with an extra copy of the 21st chromosome. Under normal conditions, there are 23 pairs, or 46 chromosomes, in the cell nucleus of a human. In individuals with Down syndrome, there is a full or partial copy of the extra 21st chromosome. The presence of an extra chromosome in the genomic structure causes some differences to be seen in the individual's physical and mental development.

Down syndrome, first described in 1866 by an English physician named John Langdon Down, was linked to the 21st chromosome approximately 100 years later by Dr. Jerome Lejeune. Down syndrome is currently the most common type of chromosomal anomaly. Research shows that Down syndrome occurs in 1 out of every 1000 births each year. However, this rate may vary from region to region and even according to ethnic groups. For example, it may be more difficult to detect the physical symptoms of Down syndrome in people with darker skin tones. According to experts, the biggest risk factor for the emergence of this syndrome is maternal age. As maternal age increases, especially in pregnancies over the age of 35, the risk of chromosomal anomaly can increase significantly. Various studies show that this rate reaches 16.65 per 1000 births in mothers over the age of 45.

Down syndrome can manifest itself with differences in the palm line, eye shape, and muscle tone. In addition, since mental development problems can also be seen in individuals with Down syndrome, learning difficulties may be encountered. However, Down syndrome is not a disease, but a difference. For this reason, education and social support provided at an early age play an important role in the physical and mental development of individuals.

What Are the Types of Down Syndrome?

Although Down syndrome is a chromosomal anomaly that occurs due to an extra copy of the 21st chromosome, it is divided into different types within itself. The understanding that Down syndrome is a chromosomal anomaly began in 1959 when French scientists Lejeune, Gautier, and Turpin discovered the 47th chromosome by examining the cells of children with Down syndrome under a microscope. It was then understood that this chromosome was actually a 3rd copy of the 21st chromosome. However, it is observed that while some individuals with the syndrome have a full copy of this chromosome, others have a partial copy. The types of Down syndrome are determined according to this difference. Accordingly, the main types of Down syndrome are as follows:

Trisomy 21: Trisomy 21 is the most common type of the syndrome. For this reason, Down syndrome is often referred to as trisomy 21. Approximately 95% of cases have the trisomy 21 type. In people with the trisomy 21 type, three copies of the 21st chromosome are found in all cells due to an error that occurs during cell division.

Translocation: Translocation Down syndrome accounts for less than 4% of cases. In this type of Down syndrome, a part or all of the 21st chromosome is attached to a different chromosome. Unlike trisomy, there is no extra chromosome copy in this type of syndrome. The chromosome count of these individuals is 46. However, in these individuals, an extra part of the 21st chromosome is attached to another chromosome.

Mosaic Down syndrome: The characteristics of mosaic Down syndrome are slightly different. In this type of syndrome, which constitutes approximately 1% of cases, an extra chromosome copy is found in some of the cells, while the chromosome count of the others is 46.

Types of Down syndrome are the main reason why the symptoms of the syndrome and educational needs vary from person to person.

How Does Down Syndrome Occur?

It is not known exactly why and how Down syndrome occurs. Most of the time, an abnormal cell division that occurs for various reasons during the development of the male reproductive cell, the sperm, or the female reproductive cell, the egg, or during the early development period of the baby in the mother's womb, causes the syndrome to emerge. In some individuals, translocation Down syndrome can show genetic transmission. For this to occur, both parents usually need to have translocation Down syndrome. Although the causes of Down syndrome are not known for certain, various studies conducted for many years show that some factors may increase the risk of Down syndrome. Accordingly, the main risk factors are as follows:

Age: Various studies show that advanced maternal age is the main risk factor for the emergence of the syndrome. Getting pregnant at age 35 or older may increase the risk of giving birth to a child with this syndrome. However, when looking at studies on children with Down syndrome, it is seen that the mother's age is under 35 in the vast majority of them. The reason for this is that the number of children is higher in women under 35.

Having a child with Down syndrome: The risk of the syndrome occurring in other children of those who have previously given birth to a child with Down syndrome may be higher.

Today, thanks to early screening tests performed during pregnancy, the risk of Down syndrome can be detected in the early period. In addition, some physical and mental differences seen after birth can help in noticing Down syndrome in the early period. Accordingly, the main symptoms of Down syndrome are as follows:

The face being flatter than normal

The nasal bridge being flatter

The head being smaller and the neck being short

A crease in the palm called a palmar crease

Feet being smaller than normal

Tiny, white spots called Brushfield spots on the colored part of the eye

Weak muscle tone in infancy

Excessively flexible joints

The little finger being curved toward the thumb

In addition to the physical symptoms listed, the syndrome can also manifest itself with some mental and behavioral problems. The chromosomal difference in the child can cause differences in cognitive processes such as speech skills, motor skills such as walking, and learning. Also, children with Down syndrome may be prone to stubbornness or temper tantrums. The main cognitive symptoms seen in individuals with Down syndrome are as follows:

Delay in language and speech skills

Delay in gross motor skills such as crawling, walking, and climbing, and fine motor skills such as grasping objects

Learning disability

Difficulty in concentration

Difficulty in making decisions

In some individuals with Down syndrome, some congenital or later-emerging health problems may be encountered more frequently due to differences experienced during the development process in the womb. Some of these health problems are as follows:

Ear infections or hearing loss

Vision problems

Oral and dental diseases

Being more prone to infections or diseases

Obstructive sleep apnea

Cardiovascular diseases

Thyroid gland diseases

Digestive system problems such as reflux and constipation

Experts regularly monitor health problems that may be seen in addition to the syndrome throughout the individual's life and determine the appropriate treatment plan for the person when necessary.

How is Down Syndrome Diagnosed?

A diagnosis of Down syndrome can be made with the help of various tests performed during pregnancy or after birth. The Down syndrome test performed before birth is examined in two classes: screening tests and diagnostic tests. Accordingly, the screening tests performed during pregnancy are as follows:

First-trimester screening tests: These tests, performed between the 11th and 14th weeks of pregnancy, that is, in the first three-month period, measure the levels of pregnancy hormone known as plasma protein-A (PAPP-A) and human chorionic gonadotropin (HCG) in the expectant mother's blood. Results outside the normal range may indicate a problem with the baby. In addition, more fluid may collect in the neck area in babies with chromosomal anomalies. For this reason, the nuchal translucency test, also known as the Down syndrome nuchal translucency test, where the fetus's neck thickness is measured with ultrasound in the first trimester, can also be utilized.

Second-trimester screening tests: The levels of some proteins in the mother's blood can be measured with triple screening tests and quadruple screening tests between the 16th and 18th weeks of pregnancy. Abnormalities seen in alpha-fetoprotein, estriol, HCG, and inhibin A protein levels may indicate a chromosomal anomaly in the baby.

Cell-free DNA tests: A small amount of the fetus's DNA is released into the mother's blood through the placenta. This cell-free DNA in the blood can be examined for the 21st chromosome using various methods.

The tests listed above are not sufficient for a definitive diagnosis. If the Down syndrome test result is positive or there is uncertainty, experts may deem it appropriate to perform further tests. The main methods used by experts to confirm the diagnosis in cases where they suspect symptoms of Down syndrome in babies in the womb are as follows:

Amniocentesis: Chromosome analysis can be performed by taking a sample from the amniotic fluid, that is, the baby's water. During amniocentesis, which is usually performed between the 15th and 20th weeks of pregnancy, experts take a fluid sample from the uterus with the help of a needle. Examining the taken fluid in a laboratory environment can help make a definitive diagnosis.

Chorionic villus sampling (CVS): During chorionic villus sampling, experts enter through the cervix with the help of a thin cannula and take a sample from the placental tissue to examine it under a microscope.

In addition to the examinations performed during pregnancy, a diagnosis of Down syndrome can also be made with genetic analyses performed after birth.

Is There a Treatment for Down Syndrome?

Since Down syndrome is not a disease but a difference, there is no cure for the syndrome. However, experts act with a multidisciplinary approach to help individuals with Down syndrome learn how to live with this syndrome and improve their quality of life. Every child with Down syndrome is different. For this reason, education and social support programs are prepared according to the individual's needs. The main support programs prepared for individuals with Down syndrome and their families are as follows:

Programs aimed at improving sensory skills

Programs aimed at improving social skills

Programs aimed at enabling the person to be self-sufficient

Physical therapy or occupational therapy programs

Speech therapy

Treatment and follow-up of accompanying other health problems

It is important that parents or those responsible for the care of children also participate in Down syndrome support programs. In this way, they can help their children become self-sufficient.

Frequently Asked Questions

Down syndrome is a genetic difference caused by the presence of an extra copy of the 21st chromosome or the attachment of all or part of the 21st chromosome to another chromosome. Autism spectrum disorder, on the other hand, is a neurodevelopmental disorder that manifests itself with symptoms such as deficiencies in social interaction and communication, and repetitive behaviors as a result of the different functioning of the brain region responsible for determining communication with the environment. Down syndrome can be seen in anyone, regardless of ethnic origin and economic welfare level. However, women who become mothers at age 35 or older, those who have a child with Down syndrome or another chromosomal disorder, or those who have a chromosomal disorder themselves may have a higher risk of having a child with Down syndrome. Down syndrome can lead to mild to moderate intellectual disability. Various studies point to Down syndrome as the most common cause of intellectual disability worldwide. It is normal for people with Down syndrome to have a certain level of mental developmental delay. However, with education and support programs prepared specifically for the individual, they can reach their maximum potential and easily adapt to social life. Children with Down syndrome may start talking 9-12 months later than their peers. Children with Down syndrome may start speaking their first words between the ages of 1-4. They can form two-word sentences between the ages of 2 and 7.5. However, thanks to speech therapies started in the early period, they can acquire skills such as imitating sounds, even if they cannot say their first words until they are 2-3 years old. The main reason why people with Down syndrome resemble each other is the presence of a partial or full extra copy of the 21st chromosome. This genetic difference can cause common physical characteristics. However, it should not be forgotten that although they carry common physical characteristics, every individual is different. Today, thanks to the widespread use of education and support programs and the close monitoring of individuals with the syndrome in terms of accompanying health problems, the life expectancy for Down syndrome has reached 60 years and over.

Down syndrome can be detected with tests performed in the early period, and the development of individuals can be contributed to with appropriate support programs. If you want to get an expert opinion for your child and have the necessary checks done, you can make an appointment with our Hisar Hospital Intercontinental Department of Pediatrics immediately. Early diagnosis is the first step to a healthy future.