Trisomy 21
(Down Syndrome)

It is caused by the abnormal division of the 21st chromosome, resulting in three copies of the chromosome instead of the usual two. A chromosomal abnormality where there is one more chromosome than usual is called a trisomy, and Down syndrome is also called trisomy 21 because there are three copies of the 21st chromosome.

Down syndrome (trisomy 21) is classified into three types based on chromosomal structure: standard, translocation, and mosaic.^※2

<Standard Type>
This type is observed in approximately 95% of Down syndrome cases and occurs when three copies of chromosome 21 are present instead of the usual two.
It is caused by the failure of chromosomes to separate properly during the formation of eggs or sperm.

<Translocation Type>
This occurs in approximately 3-4% of all Down syndrome cases and is caused by chromosomal translocation, where part of chromosome 21 breaks off and attaches to another chromosome.

<Mosaic Type>
This is found in approximately 1-2% of all Down syndrome cases, where a mixture of cells with chromosomal abnormalities and cells with a normal chromosome count coexists in the body. Depending on the proportion of cells with chromosomal abnormalities, Down syndrome symptoms may be milder.

While symptoms vary from person to person, there are several common physical characteristics and health issues.^※3

<Physical Characteristics>
・Flat facial features
・Enlarged tongue
・Upward slanting eyes
・Fingerprint patterns running horizontally
・A single deep crease across the palm

<Cognitive and Developmental>
・Delayed growth
・Delayed speech development
・Learning and intellectual disabilities
・Attention and concentration issues

<Health Issues>
・Heart disease, especially congenital heart disease
・Hearing impairment
・Vision problems, such as strabismus
・Digestive system issues; susceptibility to infections due to a weak immune system
・Hormone-related problems such as hypothyroidism
・Increased risk of leukemia and other blood disorders

These symptoms can present in varying degrees depending on the individual. In addition, individuals with Down syndrome have diverse abilities and personalities, and with the provision of appropriate support and resources, it is often possible to live a fulfilling life.

Down syndrome is a genetic congenital condition, and there is no cure for the underlying cause.
However, many interventions are implemented to support the health, growth, and development of individuals with Down syndrome. Major therapies include the following:^※4

<Physical Therapy>
Through play-based activities, physical therapy promotes the acquisition of motor skills necessary for daily life. For instance, basic movements such as crawling and rolling over are practiced during infancy, while more complex movements like walking, running, and climbing stairs are trained from childhood through school age.

<Occupational Therapy>
Occupational therapy trains individuals to acquire necessary skills through actual daily activities, such as drawing, studying, exercising, dressing, and using scissors or chopsticks. The goal is to improve the ability to perform activities in daily life.

<Speech-Language Therapy>
Practices word pronunciation and comprehension using cards showing animals, food, etc. This approach focuses on improving language ability and helping the development of communication skills.

Each person with Down syndrome has their own personality and grows at their own pace.
It is important to consider the medical care, developmental support, and family assistance needed for children with Down syndrome.

Thanks to these medical advances, the average life expectancy for individuals with Down syndrome has more than doubled in the last 30 years.
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