What is Down Syndrome?
Down syndrome is a chromosomal disorder caused by the presence of an extra copy of chromosome 21. Normally, humans have 46 chromosomes in each cell, divided into 23 pairs. In Down syndrome, there is an extra chromosome in the 21st pair, making a total of three copies instead of the usual two. This additional genetic material disrupts normal development, resulting in the characteristic features and developmental delays associated with the condition.
Down syndrome is the most common chromosomal condition diagnosed in the United States, occurring in approximately 1 in every 700 births. While it is a lifelong condition, individuals with Down syndrome can lead fulfilling lives with appropriate support, education, and medical care.
Symptoms of Down Syndrome
The symptoms of Down syndrome can vary widely among individuals but generally include a combination of physical and intellectual characteristics. Common signs and symptoms include:
Physical Features
- Distinct Facial Features: Individuals often have a flat facial profile, particularly the bridge of the nose, and almond-shaped eyes that may slant upward.
- Short Stature: Children with Down syndrome typically grow more slowly and may remain shorter than their peers.
- Low Muscle Tone (Hypotonia): Reduced muscle tone can lead to delays in motor skills development, such as sitting, crawling, and walking.
- Single Palmar Crease: A single crease across the palm of the hand is a common trait.
- Short Neck: A shorter neck with excess skin at the back is frequently observed.
- Small Ears and Mouth: These features can contribute to speech delays and hearing issues.
Intellectual and Developmental Delays
- Cognitive Impairment: Ranging from mild to moderate, cognitive delays affect learning and problem-solving abilities.
- Speech and Language Delays: Children may begin speaking later and have difficulties with articulation and vocabulary.
- Delayed Motor Skills: Fine and gross motor skills may develop more slowly, affecting activities like writing or running.
Health-Related Issues - Congenital Heart Defects: Approximately half of the children with Down syndrome are born with heart defects, which may require surgical intervention.
- Hearing and Vision Problems: Increased risk of ear infections, hearing loss, and vision issues such as cataracts or strabismus.
- Thyroid Disorders: Hypothyroidism is more common in individuals with Down syndrome.
- Respiratory Infections: Greater susceptibility to respiratory issues due to anatomical differences and immune system challenges.
Causes of Down Syndrome
Down syndrome is caused by an error in cell division that results in an extra copy of chromosome 21. This condition is present from conception and is not typically inherited, although rare cases of translocation Down syndrome involve genetic material from chromosome 21 being transferred to another chromosome.
There are three primary types of Down syndrome, each resulting from the presence of an extra chromosome 21 in different ways:
- Trisomy 21: The most common form, accounting for about 95% of cases, occurs when every cell in the body has three copies of chromosome 21 instead of the usual two.
- Mosaic Down Syndrome: This rare form, present in about 1-2% of cases, occurs when some cells have an extra chromosome 21, while others have the typical two copies. The symptoms can be less pronounced compared to Trisomy 21.
- Translocation Down Syndrome: Representing approximately 3-4% of cases, this type happens when part of chromosome 21 becomes attached (translocated) to another chromosome, typically chromosome 14. This can sometimes run in families if a parent carries a balanced translocation.
- Risk Factors for Down Syndrome
While Down syndrome can occur in any pregnancy, certain factors can increase the likelihood: - Advanced Maternal Age: The risk of having a child with Down syndrome increases with the mother’s age. Women over 35 have a higher chance compared to younger women. For example, at age 25, the risk is about 1 in 1,250, whereas at age 40, it rises to approximately 1 in 100.
- Genetic Factors: Although most cases are not inherited, translocation Down syndrome can run in families if a parent carries a balanced translocation.
Previous Child with Down Syndrome: Having one child with Down syndrome slightly increases the likelihood of having another affected child, especially in cases of translocation. - Carrier of Genetic Translocation: Parents who carry a rearrangement of genetic material involving chromosome 21 have a higher risk of having a child with Down syndrome.
It’s important to note that most children with Down syndrome are born to women under 35, simply because younger women have more babies overall.
How is Down Syndrome Diagnosed Before Birth?
Prenatal screening and diagnostic tests can identify Down syndrome during pregnancy. These tests are typically offered based on risk factors such as maternal age or family history. They fall into two categories: screening tests and diagnostic tests.
- Screening Tests: Screening tests estimate the likelihood that a fetus has Down syndrome but do not provide a definitive diagnosis. They are non-invasive and pose no risk to the pregnancy.
- First-Trimester Screening: Conducted between weeks 11 and 14, this includes a blood test measuring levels of specific proteins and a nuchal translucency ultrasound to assess fluid at the back of the fetus’s neck.
- Second-Trimester Screening (Triple or Quad Screen): Performed between weeks 15 and 20, this blood test measures markers such as alpha-fetoprotein, human chorionic gonadotropin (hCG), estriol, and inhibin-A.
Integrated Screening: Combines first and second-trimester screenings to improve accuracy. - Non-Invasive Prenatal Testing (NIPT): Analyzes fetal DNA circulating in the mother’s blood, offering high accuracy for detecting Down syndrome and other chromosomal abnormalities.
- While screening tests can indicate an increased or decreased risk, they do not confirm the presence of Down syndrome. Positive results from screening tests usually lead to diagnostic testing for confirmation.
Occupational Therapy for Down syndrome
Occupational Therapy plays a vital role in supporting individuals with Down syndrome by enhancing their physical, cognitive, and social abilities. Through personalized activities, it helps improve essential skills like fine motor coordination, sensory integration, and daily living tasks, such as dressing and eating.
The therapy focuses on building independence, boosting confidence, and addressing specific developmental challenges. With a tailored approach, Occupational Therapy empowers individuals with trisomy 21 to achieve their full potential and lead a more active and fulfilling life.
Discover how this therapy can make a positive difference in their journey toward self-reliance and well-being.