Down syndrome is one of the most
common genetic syndromes, occurring in one of 800 to 1,000 live births.1 In
approximately 95 percent of cases, the syndrome is caused by simple trisomy due
to nondisjunction (nonsegregation) of chromosome 21 in the formation of the
oocyte or spermatocyte. In 4 to 5 percent of cases, the syndrome is caused by a
translocation (link) of one chromosome 21 to another, usually a chromosome 14
or the other chromosome 21. The remaining 1 percent of cases are mosaics (more
than one cell line) caused by nondisjunction occurring after conception.
Although babies with Down
syndrome can be healthy as any other children or they can also have special
medical problems. The good news is that medical treatments have improved
substantially, and the vast majority of babies with Down syndrome grow up
healthy and active.
Risk of Medical Problems
Children with Down syndrome are
at an increased risk for a wide range of medical problems. These potential
problems include congenital heart defects, increased susceptibility to
infection, respiratory problems, gastrointestinal disorders, and childhood
leukemia. However, not every baby with Down syndrome develops health problems
and most of these health problems are now treatable.
Congenital Heart Defects
A congenital heart defect is a
heart problem that is present at birth. Between 30 and 45 percent of babies
with Down syndrome are born with heart defects. These defects vary from mild
defects which may disappear with time to severe defects which will require
major surgery. In most cases a cardiologist can detect a heart defect soon
after birth.
The most common congenital heart
defect is Atrioventricular (AV) Septal Defect. This problem occurs when
the valves separating the atrium (upper chamber of the heart) from the
ventricle (lower chamber of the heart) leak allowing blood to flow in the wrong
direction. This problem is quite serious but can corrected with surgery in
infancy. The second most common problem is a hole in the wall of either the
ventricles (Ventricular Septal Defect or VSD) or between the atrium (Atrial
Septal Defect or ASD). Small holes do not cause any strain on the baby and
often close by themselves. Larger holes may require surgery. Babies with heart
defects sometimes show symptoms. These symptoms can include feeding problems, a
change in color during feeding, poor growth, and labored breathing.
Endocrine Problems
The endocrine system is made up
of the glands that produce and secrete hormones. These include the thyroid, the
pituitary gland, the adrenal glands, the pancreas and many others. The most
common endocrine problem in children with Down syndrome involves the thyroid.
The thyroid, located in the throat, is the largest endocrine gland in the body.
The thyroid secretes a wide array of hormones that regulate metabolism, heart
rate, and growth.
The most common type of thyroid
problem both among the general population and children with Down syndrome is
hypothyroidism.
- Hypothyroidism means that the thyroid is not producing sufficient amounts of hormones. Hypothyroidism can be a serious problem if left untreated so it is important that children with Down syndrome be tested at birth and then on a yearly basis to insure that the thyroid is working correctly. Untreated, hypothyroidism can lead to slow growth, skin disorders, blood disorders, sleep disorders, learning disorders, and feeding disorders. Fortunately, hypothyroidism can be easily treated with an oral medication, L-thyroxine. This is an inexpensive medication which serves to replace the missing hormones.
- Hyperthyroidism is a condition where the
thyroid produces too much thyroid hormone. One form of this condition is
Children with Down syndrome may
have a shortage of growth hormone (hGH) which is produced in the pituitary
gland. hGH replacement is fairly controversial, but a child with reduced levels
of hGH may be a candidate for hGH replacement therapy. It is quite common for
children with genetic disorders such as Down syndrome to be short in stature
and special growth charts have been developed for children with Down syndrome.
However, some doctors have come to believe that children with Down syndrome
should be charted on the normal growth charts. If a child fails to grow on
these charts, it may be a sign that there is an endocrine problem such as
hypothyroidism or hypopituitarism.
Skin Problems
Infants with Down syndrome tend
to have very soft skin but as they grow older their skin can become dry and
coarse.
- A common problem for children with Down syndrome is Atopic Dermatitis (also called atopic eczema). This is a condition where the child has a dry, red, and scaly rash usually on the cheeks, arms, legs, or trunk. This condition is actually found in up to 10% of all children but is more common in children with Down syndrome. No permanent cure exists but the condition can be controlled. The skin should be treated with moisturizers and mild soaps or soap-free cleansers (such as Cetaphil) should be used to clean the skin. More severe cases should be treated by a dermatologist who can prescribe topical corticosteroids. Some parents have reported successfully treating atopic dermatitis by eliminating dairy and gluten (found in wheat) products from the diet. Some kids have atopic dermatitis on cheeks and chin. Replacement of cow milk with soy milk and switching to rice cereals can show dramatic improvement in skin condition in a very short time.
- Alopecia Areata (AA) is an autoimmune disease involving the hair and nails. Although rare, it does tend to occur more often in people with Down syndrome. It is believed that AA is an autoimmune reaction where the body attacks its own hair follicles. A person with AA usually develops bald patches although generalized thinning or complete baldness may also occur. In most cases, children with AA may have a few small patches that disappear without treatment within one year. AA can be treated with topical steroids or topical irritants but in young children these treatments are usually not practical.
Gastrointestinal Problems
The gastrointestinal (GI) tract
consists of the parts of the body that take in food, extract the nutrients, and
dispose of the waste. Gastrointestinal problems tend to be more common in
children with Down syndrome than in the normal population, however most of
these conditions are rare. Gastrointestinal problems fall into two basic area:
- anatomical anomalies - the structure of the organs is abnormal
- functional disorders - the organs do not work the way they should
The most common anatomical
anomalies are:
- Aganglionic Megacolon - Also called Hirschsprung's disease, this is a condition where parts of the bowel have no nerve cells. Children with this condition can become extremely constipated. Severe cases can be life threatening if left untreated. Hirschsprung's is normally treated by surgically removing the part of the bowel that does not function correctly.
- Annular Pancreas - This is a condition in which the pancreas is ring-shaped and constricts part of the intestine. Depending on the amount of constriction, this can be a serious medical emergency. This condition is normally treated surgically.
- Duodenal Atresia and Duodenal Stenosis - Both of these conditions involve a narrowing of the small intestine the difference being the amount of the narrowing. In duodenal atresia, the first part of the intestine where it connects to the stomach is completely blocked off. Since no food can pass from the stomach into the intestines, this condition must be treated immediately by surgically removing the blocked part of the intestine. A duodenal stenosis involves a narrowing of the intestine. Depending on the amount of narrowing, surgery may be required. In less serious cases, the condition may be managed through diet.
- Imperforate Anus - This is a condition in which the anus (the external opening of the colon) is blocked. This condition is normally treated with surgery within the first few days after the baby is born.
- Tracheo-Esophageal Fistula - This is a condition where there is an opening between the windpipe and the esophagus. Some children have this condition without developing any problems. Others may require surgery to close the fistula to prevent fluids from travelling from the esophagus into the trachea.
- Pyloric Stenosis - This is a narrowing of the pylorus, the junction where the stomach empties into the small intestine. This is treated with a simple surgical procedure that usually works very well.
It is important to understand
that any of these conditions can occur in any child although they do tend to be
more common in children with Down syndrome.
The most common functional
disorders are:
- Esophageal Motility Disorders and Gastro-esophogeal Reflux. Children with Down syndrome often have problems with reflux. Reflux does not mean that the child spits up during or after a feeding. In most cases, this simply means the child has swallowed air. Reflux can occur because the esophagus is having trouble propelling food into the stomach or it may occur because the stomach is emptying too slowly. Persistent reflux may cause serious problems since the stomach contents are highly acidic and can damage the esophagus, larynx, or trachea. If the child aspirates stomach acids, they may gag or cough just after feeding. Reflux is normally treated with medicines to reduce stomach acidity and to help move food through the stomach faster. In many cases, the child may grow out of the problem.
- Malabsorption Disorders - Children with Down syndrome sometimes have a condition called celiac disease in which the intestines lose the ability to absorb nutrients. This condition is normally treated by eliminating gluten from the diet. There are other malabsorption disorders but children with Down syndrome are no more likely to have these conditions then the rest of the population. Some children with Down syndrome may have trouble absorbing certain vitamins. If the child is not growing well or has an increased number of ordinary infections that are difficult to cure, they may have a vitamin absorption problem. A blood test can help to determine if this is a problem.
Respiratory Problems
Children with Down syndrome are
at risk for Respiratory Infections. Some respiratory infections are
caused by a weak cough which is sometimes seen in children with hypotonia.
Other causes of respiratory infection are heart problems leading to fluid in
the lungs, regurgitation of food from the stomach into the lungs, and weakened
immune systems. Sleep apnea, temporary stopping of breathing during sleep, is
also sometimes seen in children with Down syndrome. Sleep Apnea is often
caused by the adenoids or tonsils being too large for the size of the mouth.
Symptoms of sleep apnea include restlessness, noisy breathing, and snoring.
This can be a serious problem since the baby may have reduced oxygen levels to
the brain. Treatment can include removing the tonsils or adenoids.
Orthopedic Problems
Children with Down syndrome
experience a wide range of orthopedic problems due to their loose ligaments and
hypotonia. These problems include scoliosis (side-to-side curvature of the
spine), joint dislocation, hip and knee cap instability, weak ankles, and
problems with the feet including pronation and flat feet. Some of these
conditions may not produce any symptoms while others may require surgery
depending on the severity.
As many as 20% of all children
with Down syndrome may have a weakness or instability in the spinal column in
the neck. This is a condition called atlanto-axial instability. This condition,
if not diagnosed, can lead to spinal cord damage which can lead to paralysis or
death. It is important that children with Down syndrome be screened for this
condition. Screening is done with both a neurological exam and with x-rays. Normally,
the screening is done between the ages of 4 and 6. Treatment will depend on the
amount of instability present and the distance separating the vertabrae. If the
condition is severe enough, surgery may be required.
Problems with Vision and Hearing
Close to 70 percent of children
with Down syndrome will have some type of vision problem. These problems
include farsightedness, nearsightednes, strabismus (crossed eyes), amblyopia
(lazy eye), astigmatism, cataracts, and blocked tear ducts. All of these problems
can be treated if detected early. All children, not just children with Down
syndrome, should have their eyes tested.
Studies suggest that 60 percent
of children with Down syndrome experience some type of hearing loss. The
development of speech depends on hearing so it is important that children be
tested to determine if they are experiencing hearing problems. Hearing loss can
be treated with antibiotics to treat infections, eustachian tubes (implanted in
a minor surgical procedure) to remove fluid from the inner ear, or, if
necessary, hearing aids. With early detection, children with Down syndrome
should be able to hear normally.
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