What Is Down Syndrome?

Down syndrome is a genetic condition caused by an extra copy of chromosome 21, also called Trisomy 21. Instead of having two copies, people with Down syndrome have three copies of chromosome 21, which affects physical growth, learning, and development.

 Types of Down Syndrome

• Trisomy 21 (95%): Every cell has an extra chromosome 21.
• Translocation (3–4%): Part of chromosome 21 attaches to another chromosome.
• Mosaic (1–2%): Only some cells have the extra chromosome, often leading to milder symptoms.

Features and Characteristics

• Physical features: flat facial profile, upward-slanting eyes, small ears, low muscle tone (hypotonia), and a single crease across the palm.
• Developmental delay: slower speech and motor development.
• Learning difficulties: mild to moderate intellectual disability.
• Health concerns (not in all cases): heart defects, thyroid problems, hearing or vision issues.

 Risk Factors

Down syndrome can happen in any pregnancy but the risk increases with maternal age, especially 35 years and older. Most cases are random and not inherited.

 Diagnosis

• Screening tests: NT scan combined with blood tests or Non-Invasive Prenatal Testing (NIPT).
• Diagnostic tests: Chorionic Villus Sampling (CVS) or Amniocentesis confirm the diagnosis.

 Living with Down Syndrome

With early medical care, therapies such as speech and physiotherapy, and family support, many people with Down syndrome live healthy and fulfilling lives.