Down syndrome: what it really is

Quick answer. Down syndrome is a chromosomal variation: people have three copies of chromosome 21 instead of two. It is not a disease, it is not contagious, and it is compatible with a long and full life.

Why it matters. There are deep myths around Down syndrome that affect how people with it are treated. Understanding what it really is — biologically — helps reject what it is not.

What the source says. According to NDSS, every cell in the body has 46 chromosomes: 23 pairs. In Down syndrome, pair number 21 has an extra chromosome (hence “Trisomy 21”). That chromosomal difference begins before birth and lasts a lifetime. It does not progress, does not worsen on its own, and is not hereditary in most cases (the most common type is spontaneous — the result of how the egg or sperm divided).

What Down syndrome is NOT: a disease (you don’t catch it or cure it), a mental disability that defines a person’s potential (the range of abilities is as wide as in any population), a sentence to dependence (there are adults with Down syndrome who live independently, work, marry), or a moral failing.

What can you do now? Read NDSS guides specifically about what you CAN expect in terms of abilities and participation in life. Actively reject myths — with friends, family, professionals — because beliefs about what is possible shape actual opportunities.

To go deeper. NDSS — Facts, Myths, & Truths About Down Syndrome: dispels common myths with evidence.

⚠️ This isn't medical advice. It describes what the cited sources say — always check with your child's pediatrician or specialist before making health decisions.