Down Syndrome

Down Syndrome is a chromosomal disorder that occurs when an individual has three copies of chromosome 21 instead of the usual two. This extra chromosome results in characteristic physical features and intellectual disabilities. 

Chromosomes are the structures that carry genes, and they are found in every cell of the body. Most people have 46 chromosomes, but people with Down Syndrome have 47. The extra chromosome results in physical and mental differences, as well as an increased risk of certain health problems. 

People with Down Syndrome typically have decreased muscle tone, reduced height, and developmental delays. They may also have distinct facial features, such as a flattened nose and small ears. 

There are three types of Down Syndrome, which are classified according to the genes involved. 

The most common type is Trisomy 21, where there are three copies of chromosome 21 instead of two. This accounts for around 95% of Down Syndrome cases. 

The second type is Mosaic Down Syndrome, where there is a mix of cells with different chromosome counts. This accounts for around 4% of cases. 

The third and rarest type is Translocation Down Syndrome, where part of chromosome 21 becomes attached to another chromosome. This accounts for around 1% of cases. 

All types of Down Syndrome result in similar physical and intellectual disabilities. Early diagnosis and intervention can help to improve the quality of life for people with Down Syndrome, but there is no cure. 

Down Syndrome is a chromosomal disorder caused by an error in cell division. The severity of the symptoms associated with Down Syndrome can vary from mild to severe, and individuals with Down Syndrome typically have a lower life expectancy than the general population. Around 1 in every 1100 babies born in Australia will have Down Syndrome, making it the most common chromosomal disorder. 

Although the cause of Down Syndrome is not fully understood, it is believed that certain environmental and lifestyle factors may increase the risk of developing the condition. These include advanced maternal age, cigarette smoking, and exposure to ionizing radiation. 

Symptoms vary from person to person, but common symptoms include low muscle tone, short stature, flattened facial features, upward-slanting eyes, poor coordination, and intellectual disability. 

Although some of the features associated with Down Syndrome are visible at birth, others may not be apparent until later in childhood. A diagnosis of Down Syndrome can be made before or after birth. Prenatal testing, which is typically done during the first or second trimester, can screen for the presence of the extra chromosome. After birth, a diagnosis can be made based on physical characteristics and/or through genetic testing.