Down Syndrome

February 1, 2017

Down syndrome is a developmental genetic disorder disorder caused by an extra copy of chromosome 21. It is by far the most common and best known chromosomal disorder in humans and the most common cause of intellectual disability.

Our bodies are made up of millions of cells. In each cell there are 46 chromosomes. The DNA in our chromosomes determines how we develop. Down syndrome is caused when there is an extra chromosome. People with Down syndrome have 47 chromosomes in their cells instead of 46. They have an extra chromosome 21, which is why Down syndrome is also sometimes known as trisomy 21. The extra chromosome is associated with other conditions such as varying degrees of developmental delay and intellectual disability, characteristic facial features, and increased risk of certain health conditions. This extra copy changes how the baby’s body and brain develop, which can cause both mental and physical challenges for the baby. The degree of these conditions varies greatly from child to child.

These children often suffer from various physical ailments, including:

Recurrent vomiting
Failure to thrive
Recurrent infections of the upper respiratory tract, including ear infections
Bed wetting
Constipation
Sleep disturbances
Hyperactivity
Autism and emotional and neurologic ailments

People with Down syndrome often experience a gradual decline in thinking ability (cognition) as they age, usually starting around age 50. Down syndrome is also associated with an increased risk of developing Alzheimer disease, a brain disorder that results in a gradual loss of memory, judgment, and ability to function. Approximately half of adults with Down syndrome develop Alzheimer disease. Although Alzheimer disease is usually a disorder that occurs in older adults, people with Down syndrome usually develop this condition in their fifties or sixties.

Down syndrome, itself, does not have a cure. But, treatment is available for many of the symptoms and conditions that can accompany the diagnosis.

Types of Down Syndrome

There are three types of Down syndrome. People often can’t tell the difference between each type without looking at the chromosomes because the physical features and behaviors are similar.

Trisomy 21 – About 95% of people with Down syndrome have Trisomy 21.With this type of Down syndrome, each cell in the body has 3 separate copies of chromosome 21 instead of the usual 2 copies.

Translocation Down syndrome – This type accounts for a small percentage of people with Down syndrome (about 3%).This occurs when an extra part or a whole extra chromosome 21 is present, but it is attached or “trans-located” to a different chromosome rather than being a separate chromosome 21.

Mosaic Down syndrome – This type affects about 2% of the people with Down syndrome. Mosaic means mixture or combination. For children with mosaic Down syndrome, some of their cells have 3 copies of chromosome 21, but other cells have the typical two copies of chromosome 21. Children with mosaic Down syndrome may have the same features as other children with Down syndrome. However, they may have fewer features of the condition due to the presence of some (or many) cells with a typical number of chromosomes.

Causes

Down syndrome occurs in about 1 in 800 newborns. About 5,300 babies with Down syndrome are born in the United States each year, and an estimated 250,000 people in this country have the condition. Although women of any age can have a child with Down syndrome, the chance of having a child with this condition increases as a woman gets older.

Genetic – Down syndrome is typically caused by what is called nondisjunction. Nondisjunction happens when a pair of chromosomes fails to separate during egg (or sperm) formation. When that egg unites with a normal sperm to form an embryo, the embryo ends up with three copies of chromosome 21 instead of the normal two. The extra chromosome is then copied in every cell as the baby develops. Interestingly, nondisjunction events seem to occur more frequently in older women. This may explain why the risk of having a baby with Down syndrome is greater among mothers age 35 and older.

Risk Factors

Down syndrome occurs in people of all races and economic levels, though older women have an increased chance of having a child with Down syndrome. All 3 types of Down syndrome are genetic conditions (relating to the genes), but only 1% of all cases of Down syndrome have a hereditary component (passed from parent to child through the genes). Heridity is not a factor in trisomy 21 (nondisjunction) and mosaicism. However, in one third of cases of Down syndrome resultuing from translocation there is a heriditary compontent – accounting for about 1% of all cases of Down syndrome. The risk factors include –

Advancing maternal age – A woman’s chances of giving birth to a child with Down syndrome increase with age because older eggs have a greater risk of improper chromosome division. By age 35, a woman’s risk of conceiving a child with Down syndrome is about 1 in 350. By age 40, the risk is about 1 in 100, and by age 45, the risk is about 1 in 30. However, most children with Down syndrome are born to women under age 35 because younger women have far more babies.

Having had one child with Down syndrome – Typically, a woman who has one child with Down syndrome has about a 1 in 100 chance of having another child with Down syndrome.

Being carriers of the genetic translocation for Down syndrome – Both men and women can pass the genetic translocation for Down syndrome on to their children.

Metal Toxicity – Since mercury and other toxic metals destroys DNA, it’s possible that they may increase the risk for Down syndrome in few cases.

Symptoms

Down syndrome can affect a child physically, cognitively, and behaviorally. Remember that every child with the condition is unique and may possess these characteristics to different degrees or not at all.

Physical

A child with Down syndrome will have some, but perhaps not all, of the following features –

Eyes that slant upward, from inner corner to outer corner
Small ears that may fold over slightly at the top
A smaller than average mouth, and larger appearing tongue
A smaller than average nose, with a flattened nasal bridge
Short, stocky arms and legs. Some children also have a wide space between the big toe and second toe.
Some babies with Down syndrome have short necks and small hands with short fingers
One single crease that goes straight across the palm, and a second crease that curves down by the thumb, rather than having three creases in the palm of the hand
Shorter than average height
Low muscle tone (hypotonia) throughout the body and increased looseness or flexibility in the joints

Developmental, Cognitive, and Behavioral Symptoms

Most children with Down syndrome have delays in meeting developmental milestones. They typically learn to walk and talk at later times than children without Down syndrome.
Children with Down syndrome often have mild to moderate cognitive impairment and intellectual disability
Children with Down syndrome often have specific patterns of cognitive and behavioral features including –
- Strengths in in social engagement and social behavior, visual learning, and word reading.
- Challenges with attention span, verbal memory, and expressive communication.
Tailored and specialized educational programs and support enable children with Down syndrome to learn and grow at their own pace.
Behavioral problems such as stubborrness, impulsivity, and temper tantrums may be more common in children with Down syndrome
A child may use “self talk” (talking out loud to himself) as a way of understanding and processing information

Down syndrome is not a progressive condition. Therefore, symptoms do not get progressively worse over time. However, some of the complications associated with Down syndrome can occur at different stages in a child’s life.

Complications

Many people with Down syndrome have the common facial features and no other major birth defects. However, some people with Down syndrome might have one or more major birth defects or other medical problems. Some of the more common health problems among children with Down syndrome are –

Hearing loss (up to 75% of people with Down syndrome may be affected)
Obstructive sleep apnea, which is a condition where the person’s breathing temporarily stops while asleep (between 50 -75%)
Ear infections (between 50 -70%)
Eye diseases (up to 60%), like cataracts and eye issues requiring glasses
Heart defects present at birth (50%)

Other less common health problems among people with Down syndrome include –

Intestinal blockage at birth requiring surgery
Hip dislocation
Thyroid disease
Anemia (red blood cells can’t carry enough oxygen to the body) and iron deficiency (anemia where the red blood cells don’t have enough iron)
Leukemia in infancy or early childhood
Hirschsprung disease
Pulmonary hypertension, a condition that affects arteries in the heart and lungs, and which often resolves in the newborn period.
Atlantoaxial instability (cervical spine vertebrae may be more flexible causing a small but increased risk for spinal cord injury or compression).
Obesity/Overweight

Health care providers routinely monitor children with Down syndrome for these conditions. If they are diagnosed, treatment is available.

Treatment

There is no cure for Down syndrome. But physical therapy and/or speech therapy can help people with the disorder develop more normally. Screening for common medical problems associated with the disorder, followed by corrective surgery, can often improve quality of life. Moreover, enriched environments significantly increase children’s capacity to learn and lead meaningful lives.

When breast-feeding, the baby should be well supported and fully awake. The baby may have some leakage because of poor tongue control. However, many infants with Down syndrome can successfully breast-feed.

If the person has any heart defects or other heart problems, antibiotics may need to be prescribed to prevent a heart infection called endocarditis.

Special education and training is offered in most communities for children with delays in mental development. Speech therapy may help improve language skills. Physical therapy may teach movement skills. Occupational therapy may help with feeding and performing tasks. Mental health care can help both parents and the child manage mood or behavior problems. Special educators are also often needed.

Alternative & Complementary Treatment

Various traditional and alternative treatment methods for Down syndrome have been popular over the years including the use of pituitary extract, glutamic acid, thyroid hormone, 5-hydroxytryptophan, dimethyl sulfoxide (DMSO), dihydroepiandosterone, sicca cell therapy and growth hormone.

Physical therapy includes activities and exercises that help build motor skills, increase muscle strength, and improve posture and balance.

Speech-language therapy can help children with Down syndrome improve their communication skills and use language more effectively.

Occupational therapy helps find ways to adjust everyday tasks and conditions to match a person’s needs and abilities.

Emotional and behavioral therapies work to find useful responses to both desirable and undesirable behaviors. Children with Down syndrome may become frustrated because of difficulty communicating, may develop compulsive behaviors, and may have Attention Deficit Hyperactivity Disorder and other mental health issues. These types of therapists try to understand why a child is acting out, create ways and strategies for avoiding or preventing these situations from occurring, and teach better or more positive ways to respond to situations.

Vitamins – Deficiencies of vitamin A vitamin B12 and vitamin C in individuals with Down syndrome have been reported.

Minerals – A considerable number of studies have looked at the role of zinc in Down syndrome. Serum levels of zinc have been reported as below normal, as well as plasma levels and whole blood levels. One study, however, did not find a general deficiency.Whole blood levels and plasma levels of selenium have also been reported to be below normal in children and adults with Down syndrome.

Amino acids – Imbalances in amino acid levels have been claimed in adults with Down syndrome.

Probiotics – Probiotics Can Alleviate GI Problems Of Down’s Syndrome Patients.

Tryptophan, Serotonin, Melatonin – Down’s syndrome individuals frequently show low serum tryptophan levels. Whether this deficiency is primary (poor tryptophan absorption) or secondary (increased tryptophan catabolism) is not known. Regardless of the cause, low tryptophan levels impair protein synthesis (tryptophan is usually a rate-limiting amino acid) and decrease serotonin levels (tryptophan is the precursor to serotonin). Serotonin is the brain neurotransmitter that not only regulates emotional control and sleep quality, but helps influence carbohydrate feeding behavior. People with low serotonin levels tend to have carbohydrate cravings.

Glutamine and Arginine – One of the key ammonia-carrying molecules in the brain is glutamine, an amino acid which tends to accumulate in Down’s syndrome. Glutamine is made from glutamate (glutamic acid) by the addition of one ammonia molecule, and from alpha-ketoglutarate by the addition of two ammonia molecules. Due to the general overabundance of ammonia in Down’s syndrome, alpha-ketoglutarate is the ideal precursor to supplement the glutamate/glutamine pathways without increasing the ammonia burden.

Collagen – The collagen connection to Down’s syndrome is fairly obvious. Newborn infants and children exhibit extreme joint laxity. In addition, structural defects in the formation of the heart affect roughly half of all Down’s syndrome individuals. Of the dozen-plus collagen genes that have been discovered, two of them reside near the tip of the 21st chromosome.

Reference –

http://www.healthline.com/health/down-syndrome#Treatment7

http://www.downs-syndrome.org.uk/about-downs-syndrome/

http://www.superduperinc.com/handouts/pdf/116_Down_Syndrome.pdf

http://www.ndss.org/Global/Aging%20and%20Down%20Syndrome.pdf

https://umm.edu/health/medical/ency/articles/down-syndrome

http://www.childrenshospital.org/conditions-and-treatments/conditions/down-syndrome

https://www.worlddownsyndromeday.org/

http://learn.genetics.utah.edu/content/disorders/chromosomal/down/

https://www.genome.gov/19517824

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4066992/

http://www.downs-syndrome.org.uk/about-downs-syndrome/