Down Syndrome: What Is It, Symptoms, and Causes?

Down syndrome is a genetically based disorder commonly seen in society. Individuals with Down syndrome may experience various complications related to the condition, but thanks to the advancements in medical care, people with Down syndrome can lead long and healthy lives.

What is Down Syndrome?

Down syndrome is a genetic disorder. In healthy individuals, there are a total of 46 chromosomes, including two sex chromosomes (XX or XY). Chromosomes are structures that contain the DNA of an individual and are wrapped in proteins. They are found in the nucleus of cells and control the cell's functions. Each chromosome exists in two copies, one from the mother and one from the father. Therefore, excluding the sex chromosomes, the remaining 44 chromosomes are in 22 pairs. In individuals with Down syndrome, a problem occurs during cell division, resulting in three copies of the 21st chromosome instead of the usual two copies. As a result, individuals with Down syndrome have a total of 47 chromosomes instead of 46. Because of the extra copy of the 21st chromosome, Down syndrome is also called Trisomy 21.

The severity of the condition can vary among individuals with Down syndrome. Some may have mild symptoms, while others may exhibit more severe symptoms. Intellectual disability is common in people with Down syndrome. In addition, children with Down syndrome may lag behind their peers in developmental milestones. Aside from the mental effects, Down syndrome can also cause problems in various organs and systems such as the digestive system and the heart.

It is important for the families of individuals with Down syndrome to be aware of this genetic condition and make educational and social life arrangements based on the needs of the individual with the syndrome. This can positively contribute to the quality of life of individuals with Down syndrome.

Complications Associated with Down Syndrome:

People with Down syndrome may develop many different complications related to the condition. These complications may become more prominent as the individual ages. Some of the complications associated with Down syndrome include:

• Heart Defects: About half of babies born with Down syndrome have a heart defect. In some cases, the defect may be serious enough to threaten life, requiring emergency surgery to correct the issue.
• Digestive System Defects: Individuals with Down syndrome often have defects in various parts of the digestive system, including the intestines, esophagus, and anus.
• Immune Disorders: Due to abnormalities in the immune system, individuals with Down syndrome are at risk for autoimmune diseases, certain types of cancer, and infectious diseases.
• Sleep Apnea: Differences in the bone and soft tissue structures of individuals with Down syndrome make them more prone to sleep apnea.
• Obesity: People with Down syndrome are at a higher risk of obesity compared to the general population.
• Spine Problems: Some individuals with Down syndrome have a misalignment of two vertebrae in the neck. This can increase the risk of spinal cord injury, especially if the head is tilted too far backward.
• Leukemia: Young children with Down syndrome are at an increased risk of leukemia.
• Dementia: Individuals with Down syndrome have a higher risk of developing dementia, which typically begins around the age of 50.
• Other Issues: People with Down syndrome may also experience a range of other health issues, including endocrine disorders, dental problems, vision impairments, and ear infections.

What Are the Symptoms of Down Syndrome?

The symptoms of Down syndrome vary greatly among individuals. Intellectual disability and developmental delays in people with Down syndrome can range from mild to moderate to severe. While some individuals with Down syndrome are physically healthy, others may have serious heart diseases or other health problems.

Common symptoms seen in individuals with Down syndrome include:

• Flattened face
• Short neck
• Small head size
• Protruding tongue
• Almond-shaped, small, slanted eyes
• Unusual-shaped or small ears
• Weak muscle tone
• Wide, small hands with a single crease in the palm
• Short fingers and toes
• Increased flexibility
• Small white spots on the iris (Brushfield spots)
• Short stature

In Down syndrome, characteristics such as height and weight can differ among individuals. However, people with Down syndrome generally develop more slowly compared to their peers and tend to remain shorter in stature as they grow.

Most individuals with Down syndrome experience mild to moderate intellectual disability. These individuals may have delayed language development and may encounter issues related to both short- and long-term memory.

What Causes Down Syndrome?

Down syndrome occurs due to the presence of three copies of the 21st chromosome instead of the normal two. The symptoms and complications associated with the syndrome are fundamentally caused by this genetic issue.

There are several mechanisms that can lead to the presence of three copies of the chromosome. These mechanisms are as follows:

• Trisomy 21: About 95% of Down syndrome cases involve trisomy 21, where the 21st chromosome has three copies instead of two. This condition affects all cells in the body and occurs due to an abnormality in cell division in either the sperm or egg that formed the individual.
• Mosaic Down Syndrome: In the rare case of Mosaic Down Syndrome, some cells contain two copies of the 21st chromosome, while others contain three. This happens due to some cells dividing normally and others abnormally after fertilization.
• Translocation Down Syndrome: Down syndrome can also occur when a portion of the 21st chromosome attaches to another chromosome, a condition known as translocation. Individuals with this form of Down syndrome carry two copies of the 21st chromosome and additional 21st chromosome material attached to another chromosome.

The question, "Is Down syndrome hereditary?" is frequently asked. Down syndrome is usually not an inherited condition. It occurs due to abnormal cell division in the early stages of fetal development. However, Translocation Down syndrome can be passed from parent to child. Translocation Down syndrome accounts for about 3-4% of all Down syndrome cases, and only a small fraction of these cases are inherited from the family. Therefore, the likelihood of Down syndrome being hereditary is quite low.

There are factors that can increase the likelihood of parents having a child with Down syndrome. These risk factors are:

• Advanced Maternal Age: The likelihood of having a child with Down syndrome increases as the mother's age increases. This is due to the aging of the eggs in older women, which raises the risk of problems during cell division. The age threshold for increased risk in women is considered to be 35, although younger mothers can still have babies with Down syndrome.
• Being a Carrier of Translocation Down Syndrome: Both the mother and father can pass Translocation Down Syndrome to their child.
• Having a Child with Down Syndrome: Families who are carriers of translocation and have previously had a child with Down syndrome may have an increased risk of Down syndrome in subsequent children. These families can seek genetic counseling to understand the likelihood of Down syndrome before deciding to have another child.

With advancements in healthcare, individuals with Down syndrome can live for more than 60 years today. Early diagnosis of Down syndrome, screening for potential complications, and intervention for those complications are crucial for the individual to lead a healthy life. It is also extremely important for families to be aware of Down syndrome in order to provide the necessary education and social arrangements for the child’s special needs.

A person with Down syndrome should have regular checkups from birth by the appropriate specialists. Therefore, it is better for an individual with Down syndrome to be followed up in a comprehensive hospital.