Down syndrome is a genetic disorder caused by the presence of an extra copy of chromosome 21. This additional genetic material affects development and results in the physical and intellectual characteristics associated with the condition. It’s one of the most common chromosomal disorders.

Three Main Types

Trisomy 21: This is the most common type, accounting for about 95% of cases. In Trisomy 21, each cell in the body has three copies of chromosome 21 instead of the usual two. This extra chromosome occurs due to nondisjunction, where the chromosome pair fails to separate during the formation of the egg or sperm.

Translocation Down Syndrome: This type accounts for about 3-4% of cases. It occurs when an extra part or a whole extra chromosome 21 is attached to another chromosome (usually chromosome 14). Unlike Trisomy 21, this form is hereditary and can be passed down from parent to child.

Mosaic Down Syndrome: Mosaicism occurs in about 1-2% of Down syndrome cases. In this type, some cells have the usual two copies of chromosome 21, while others have three copies. This variation in cell makeup can result in milder symptoms compared to Trisomy 21.

Common Characteristics of Down Syndrome

Intellectual disability: People with Down syndrome often have cognitive delays, and the level of intellectual disability can vary widely among individuals.

Physical features: Individuals with Down syndrome may have distinctive physical features, such as a flat facial profile, almond-shaped eyes, a small nose, and a protruding tongue. They may also have low muscle tone.

Health issues: People with Down syndrome are more prone to certain health conditions, including heart defects, respiratory problems, and gastrointestinal issues. Regular medical check-ups and interventions may be necessary to address these concerns.

Developmental delays: Individuals with Down syndrome may experience delays in reaching developmental milestones, such as walking and talking.

It’s important to note that while they may share some physical and developmental characteristics, each person is unique, and the range and severity of symptoms can vary widely.

With appropriate support, education, and healthcare, many lead fulfilling and active lives. Advances in medical care and increased awareness have improved the quality of life for individuals with Down syndrome and their families.