What Are Some of the Features That Make Trisomy 21 Easy to Recognize

Down syndrome is a genetic disorder in which there is an extra full or partial chromosome 21. For most people with Down syndrome, this anomaly causes a host of distinctive physical characteristics as well as potential health and medical problems. The exception are those who have the relatively rare form of Down syndrome called mosaic Down syndrome, in which not all cells have an extra chromosome 21. A person with this type of Down syndrome may have all the features of full trisomy 21, a few of them, or none at all.

Many characteristics of full trisomy 21 are quite noticeable—a round face and upturned eyes, and a short, stocky build, for example. People with Down syndrome sometimes move awkwardly, usually due to low muscle tone (hypotonia) at birth that can interfere with physical development.

Down syndrome also is associated with developmental delays and intellectual challenges, though it's important to remember that the extent of these varies widely.

Technically speaking, parents and doctors look for signs of Down syndrome, rather than symptoms. These may be seen once a child is born or, in some cases, in utero.

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Physical Characteristics

The first indication a child might have Down syndrome can appear during routine prenatal testing. In a maternal blood test called the quadruple screen, elevated levels of certain substances can be a red flag for Down syndrome but do not mean a baby definitely has the disorder.

Visible Signs

On an ultrasound (an image of a developing fetus, also called a sonogram), visible signs a baby may have Down syndrome include:

Excess skin in the back of the neck (nuchal translucency)
A shorter-than-normal femur (thigh) bone
A missing nose bone

These signs prompt health providers to recommend an amniocentesis or chorionic villi sampling (CVS), both prenatal tests that examine cells taken from the amniotic fluid or the placenta, respectively and that can confirm a diagnosis of Down syndrome. Some parents opt for these tests, while others do not.

Features

People with Down syndrome share a host of recognizable facial and physical features. These are most apparent at birth and can become more pronounced with time. The obvious characteristics of Down syndrome include:

A round face with a flat profile and small nose and mouth
A large tongue that may protrude from the mouth
Almond-shaped eyes with skin that covers the inner eye (epicanthus folds)
White flecks in the colored part of the eyes (Brushfield spots)
Small ears
A small head that's somewhat flat in the back (brachycephaly)
Short neck
Clinodactyly: A single crease across the palm of each hand (normally there are two), short stubby fingers, and a pinky finger that curves inward
Small feet with a larger than normal space between the big and second toes
Short, stocky build: At birth, children with Down syndrome usually are average size, but tend to grow at a slower rate and remain smaller than other kids their age. It's also common for people with Down syndrome to be overweight.
Low muscle tone: Infants with Down syndrome often appear "floppy" due to a condition called hypotonia. Though hypotonia can and often does improve with age and physical therapy, most children with Down syndrome typically reach developmental milestones—sitting up, crawling, and walking—later than other kids. Low muscle tone may contribute to feeding problems and motor delays. Toddlers and older kids may have delays in speech and in learning skills such as feeding, dressing, and toilet training.

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Intellect and Development

All people with Down syndrome have some degree of intellectual disability or developmental delay, which means they tend to learn slowly and may struggle with complex reasoning and judgment.

There's a common misconception that children with Down syndrome have predetermined limits in their ability to learn, but this is entirely false. It's impossible to predict the degree to which a baby born with Down syndrome will be intellectually disadvantaged.

According to the international advocacy organization Down Syndrome Education (DSE), related challenges can be bucketed as follows:

Slow development of motor skills:Delays in reaching milestones that allow a child to move about, walk, and use their hands and mouth can lower their opportunities to explore and learn about the world, which in turn can affect cognitive development and impact the language skills development.
Expressive language, grammar, and speech clarity:Because of delays in developing language comprehension, most children with Down syndrome are slow to master correct sentence structure and grammar, according to the DSE. They're also likely to have problems with speaking clearly, even when they know exactly what they're trying to say. This can be frustrating and sometimes lead to behavior problems. It can even cause a child's cognitive abilities to be underestimated.
Number skills:Most children with Down syndrome find it harder to master number skills than reading skills. In fact, the DSE says that the former are typically around two years behind the latter.
Verbal short-term memory:Short-term memory is the immediate memory system that hangs on to just-learned information for short periods of time. It supports all learning and cognitive activity and has separate components for processing visual or verbal information. Kids who have Down syndrome aren't as able to hold and process information that comes to them verbally as they are to remember what's presented to them visually. This can put them at a special disadvantage in classrooms where most new info is taught through spoken language.

What is certain is that people with Down syndrome have the potential to learn throughout their lifetimes and that their potential can be maximized through early intervention, good education, high expectations, and encouragement from family, caregivers, and teachers. Children with Down syndrome can and do learn, and are capable of developing skills throughout their lives. They simply reach goals at a different pace.

Psychological Characteristics

People with Down syndrome often are regarded as particularly happy, sociable, and outgoing. While in general, this may be true, it's important to not stereotype them, even when it comes to labeling them with such positive characteristics.

People who have Down syndrome experience a full range of emotions and have their own characteristics, strengths, weaknesses, and styles—just like anyone else.

There are some behaviors associated with Down syndrome that are largely due to the unique challenges the condition presents. For example, most people with Down syndrome tend to need order and routine when dealing with the complexities of daily life. They thrive on routine and will often insist on sameness. This can be interpreted as innate stubbornness, but that's rarely what's going on.

Another behavior often seen in people with Down syndrome is self-talk—something everyone does sometimes. It's thought that people with Down syndrome frequently use self-talk as a way of processing information and thinking things through.

Complications

As you can see, it's hard to separate out some of the signs of Down syndrome from its potential complications. Keep in mind, though, that while many of the above issues pose undeniable concern, others simply chart a course for an individual that is out of "the norm." Individuals with Down syndrome and their families embrace all of this in their own ways.

That said, people with Down syndrome are more likely than otherwise healthy people to have certain physical and mental health issues. Care throughout one's life can be complicated by these additional concerns.

Hearing Loss and Ear Infections

According to the Centers for Disease Control and Prevention, up to 75 percent of children with Down syndrome will have some form of hearing loss. In many cases, this may be because of abnormalities in the bones of the inner ear.

It's important to detect hearing problems as early as possible, since being unable to hear well can be a factor in speech and language delays.

Children with Down syndrome are also at an increased risk of ear infections. Chronic ear infections can contribute to hearing loss.

Problems with Vision or Eye Health

As many as 60 percent of children with Down syndrome will have some type of vision problem, such as nearsightedness, farsightedness, crossed eyes, cataracts, or blocked tear ducts, according to the CDC. Half will need to wear glasses.

Infections

The National Institutes of Health (NIH) states, "Down syndrome often causes problems in the immune system that can make it difficult for the body to fight off infections." Infants with the disorder have a 62 percent higher rate of pneumonia in the first year of life than do other new babies, for example.

Obstructive Sleep Apnea

The National Down Syndrome Society (NSDD) reports that there is a 50 to 100% chance that a person with Down syndrome will develop this sleep disorder, in which breathing stops temporarily during sleep. The condition is particularly common in Down syndrome because of physical anomalies such as low muscle tone in the mouth and upper airway, narrow air passages, enlarged tonsils and adenoids, and a relatively large tongue. Often, the first attempt at treating sleep apnea in a child with Down syndrome is the removal of the adenoids and/or the tonsils.

Musculoskeletal Problems

The American Academy of Orthopaedic Surgeons lists a number of issues affecting the muscles, bones, and joints of people with Down syndrome. One of the most common is an upper neck abnormality called atlantoaxial instability (AAI), in which vertebrae in the neck become misaligned. It doesn't always cause symptoms, but when it does it can lead to neurological symptoms such as clumsiness, difficulty walking or an abnormal gait (e.g. limping), nerve pain in the neck, and muscle tightness or contractions.

Down syndrome also is associated with joint instability, leading to hips and knees that may easily become dislocated.

Heart Defects

About half of all babies with Down syndrome are born with heart defects, reports the CDC. These can range from mild problems that are likely to correct themselves over time to serious defects that will require medication or surgeries.

The most common heart defect seen in infants with Down syndrome is an atrioventricular septal defect (AVSD)—holes in the heart that interfere with the normal flow of blood. An AVSD may need to be surgically treated.

Children with Down syndrome who aren't born with heart problems will not develop them later in life.

Gastrointestinal Issues

People with Down syndrome tend to be at an increased risk for a variety of GI problems. One of these, a condition called duodenal atresia, is a deformity of the small tube-like structure (the duodenum) that allows digested material from the stomach to pass into the small bowel. In a newborn, this condition causes a swollen upper abdomen, excessive vomiting, and lack of urination and bowel movements (after the first few meconium stools). Duodenal atresia can be successfully treated with surgery soon after birth.

Another gastrointestinal condition of note in Down syndrome isHirschsprung disease—an absence of nerves in the colon, which can cause constipation.

Celiac disease, in which intestinal problems develop when someone eats gluten, a protein found in wheat, barley, and rye, is more common in people with Down syndrome as well.

Hypothyroidism

In this condition, the thyroid gland makes little or no thyroid hormone, which regulates bodily functions such as temperature and energy. Hypothyroidism can be present at birth or develop later in life, so regular testing for the condition should be done beginning when a baby with Down syndrome is born. Hypothyroidism can be managed by taking thyroid hormone by mouth.

Blood Disorders

These include anemia, in which red blood cells don't have enough iron to carry oxygen to the body, and polycythemia (higher-than-normal levels of red blood cells). Childhood leukemia, a type of cancer that affects the white blood cells, occurs in about 2 to 3% of children with Down syndrome.

Epilepsy

According to the NIH, this seizure disorder is most likely to occur during the first two years of the life of a person with Down syndrome or to develop after the third decade.

About half of the people with Down syndrome develop epilepsy after age 50.

Mental Health Disorders

It's also vital to understand that, despite what may appear to be innately unshakeable cheeriness, higher rates of anxiety disorders, depression, and obsessive-compulsive disorder have all been reported in Down syndrome. These psychological problems can be successfully treated with behavior modification, counseling, and sometimes medication.

Frequently Asked Questions

Why do people with Down syndrome look the same?

They have an extra chromosome or part of an extra chromosome. Researchers believe that this extra genetic material affects growth of the maxilla (part of the skull) and the bone, cartilage, and connective tissue in the head, known as the cranial neural crest. It creates common Down syndrome features such as upturned, almond-shaped eyes and a smaller head.
Why do people with Down syndrome stick out their tongue?

The tongue is unusually large in many people with Down syndrome. In this condition, called macroglossia, the tongue is too big for the mouth so it protrudes out. Since babies born with Down syndrome also have impaired muscle control (and the tongue is a muscle), the condition may be especially noticeable and problematic.
Why are people with Down syndrome so happy?

People who have Down syndrome experience a full range of emotions and aren't always happy. Overall, the vast majority of people who have Down syndrome report being happy with life and liking who they are.

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Source: https://www.verywellhealth.com/symptoms-of-down-syndrome-1120463