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Down’s syndrome is a genetic condition caused by the presence of an extra copy of chromosome 21. It is one of the most common chromosomal conditions in the UK, affecting around 1 in every 1,000 babies born. This guide explains what Down’s syndrome is, how it presents and what life with it involves.
Down’s syndrome is a lifelong genetic condition caused by the presence of an extra copy of chromosome 21 in a person’s cells. In a typical human cell there are 46 chromosomes arranged in 23 pairs. In Down’s syndrome, chromosome 21 appears three times rather than twice, which is why the condition is also known as trisomy 21. This extra genetic material changes the course of development, resulting in varying degrees of intellectual disability, characteristic physical features and a higher likelihood of certain health conditions. The Down’s Syndrome Association confirms that Down’s syndrome occurs in approximately 1 in every 1,000 live births in the UK.
Down’s syndrome was first described scientifically by the English physician John Langdon Down in 1866, which is how the condition takes its name. The chromosomal basis of the condition was not identified until 1959, when the French geneticist Jerome Lejeune discovered the presence of an extra chromosome 21. Before that discovery, people with Down’s syndrome were poorly understood and often institutionalised; life expectancy in the 1940s was only around 12 years. Medical advances, improved support and greater inclusion in education and community life have transformed outcomes dramatically. According to DSMIG data, median life expectancy in the UK for people with Down’s syndrome is now 58 years, with current estimates from Intellectual Disability and Health placing the range at 60 to 65 years, and many people with Down’s syndrome living into their sixties and beyond.
The extra copy of chromosome 21 in Down’s syndrome occurs in three main forms. Trisomy 21, where every cell in the body contains three copies of chromosome 21, accounts for approximately 94 percent of cases. Translocation Down’s syndrome, where extra chromosome 21 material is attached to another chromosome, accounts for around 4 percent of cases. Mosaic Down’s syndrome, where only some cells contain the extra chromosome, accounts for approximately 2 percent of cases. The characteristics and abilities of people with Down’s syndrome are broadly similar across all three types, though mosaicism can sometimes result in a milder presentation.
Down’s syndrome in the UK today: NCARDRS data confirms that approximately 41,700 people are living with Down’s syndrome in England and Wales. The Down’s Syndrome Association confirms around 1 in every 1,000 babies born in the UK will have Down’s syndrome. Approximately 762 babies with Down’s syndrome were born in England and Wales in 2018 according to NCARDRS figures, and this figure has been broadly stable in recent years. Advances in prenatal screening have changed the prenatal landscape but have not altered the underlying birth rate significantly.
People-first language: The term “Down’s syndrome” is the standard term used in the UK, named after John Langdon Down. The Down’s Syndrome Association uses and recommends this terminology. In the United States, “Down syndrome” without the possessive is more common. The condition should not be referred to as “Down’s disease”, since it is a genetic condition rather than a disease. People with Down’s syndrome are people first; the condition is a part of who they are but does not define their identity, abilities or potential.
Down’s syndrome affects development across several areas. The nature and degree of impact varies widely between individuals.
All people with Down’s syndrome have some degree of intellectual disability, ranging from mild to moderate. Intellectual Disability and Health confirms that children with Down’s syndrome do learn to walk, talk and achieve other developmental milestones but will typically reach these later than non-disabled peers. There is wide variation in ability within the Down’s syndrome population, just as there is within any other population. Early intervention programmes and inclusive education significantly improve outcomes.
Common physical features associated with Down’s syndrome include a flattened facial profile, almond-shaped eyes with a slight upward slant, a small nose and a mouth that may be smaller than average, lower muscle tone at birth known as hypotonia and shorter stature. These features vary in how strongly they present in individual people with Down’s syndrome, and none of them limit what a person can achieve with the right support.
People with Down’s syndrome have a higher likelihood of certain health conditions, including congenital heart defects, hearing and vision difficulties, thyroid conditions, respiratory infections and, in later life, an earlier onset of dementia. NADS confirms that around 40 percent of children with Down’s syndrome have congenital heart defects, making early cardiac screening essential. With appropriate monitoring and treatment, most health conditions associated with Down’s syndrome can be well managed.
Speech and language development is typically delayed in children with Down’s syndrome, and receptive language (understanding) generally develops ahead of expressive language (speaking). Many children benefit significantly from speech and language therapy from an early age. Most people with Down’s syndrome are effective communicators and can express themselves clearly once their communication needs are understood and supported. Total Communication approaches are often used to bridge early language gaps.
Children with Down’s syndrome can and do attend mainstream schools in the UK, and many thrive in inclusive settings with appropriate support. Some children are educated in specialist provisions or special schools, depending on their individual needs and the support available. The Down’s Syndrome Association provides extensive guidance on educational placement. Children with Down’s syndrome are typically entitled to an Education, Health and Care Plan, which provides legally binding provision for their specific needs.
With appropriate support, many adults with Down’s syndrome live semi-independently or fully independently, work in paid employment, have long-term relationships and contribute to their communities. Intellectual Disability and Health confirms that people with Down’s syndrome can and do continue to learn throughout their lives. Independent living, supported housing, advocacy and employment initiatives have expanded significantly in recent decades, and many adults with Down’s syndrome live rich and fulfilling lives.
SENDhelp places specialist SEN teachers, teaching assistants and support staff in schools and provisions across North London, Bedfordshire, Buckinghamshire and Hertfordshire. If your school needs staff experienced with Down’s syndrome, we can help.
For more information on what causes Down’s syndrome at the chromosomal level, see our article on Causes of Down’s Syndrome. For information on the three types of Down’s syndrome, see our article on The 3 Types of Down’s Syndrome.
Down’s syndrome is a genetic condition caused by the presence of an extra copy of chromosome 21. This extra genetic material affects development, resulting in varying degrees of intellectual disability, characteristic physical features and an increased likelihood of certain health conditions. It is one of the most common chromosomal conditions in the UK, affecting around 1 in every 1,000 live births.
Yes. With appropriate education, support and healthcare, many adults with Down’s syndrome live semi-independently or fully independently, work in paid employment and have meaningful relationships. Life expectancy has increased dramatically from around 12 years in the 1940s to 60 to 65 years today, reflecting the enormous improvements in healthcare and inclusion over the past eight decades.
The birth rate of Down’s syndrome has remained broadly stable. Overall prevalence has risen because people with Down’s syndrome are living much longer, meaning there are more people with the condition alive at any given time than in previous generations. The increase in prenatal screening has changed the landscape of prenatal diagnosis but has not significantly altered the underlying chromosomal rate at which Down’s syndrome occurs.
Visit our Understanding Down’s Syndrome hub for more guides on causes, diagnosis, education, health conditions and independent living.
The information in this article is provided for educational purposes only and is not intended as medical advice. If you have concerns about Down’s syndrome or any health condition, speak to a qualified healthcare professional. SENDhelp Education Limited accepts no responsibility or liability for any loss or damage arising from reliance on this content. Any links to third-party websites are provided for convenience only and do not constitute endorsement of their content.
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