Babies With Down Syndrome (Trisomy 21; Trisomy G)

Down syndrome, which is also known as trisomy G or trisomy 21, occurs due to a chromosomal defect which results in several physical abnormalities as well as intellectual disability and growth retardation.

  • Occurrence of an extra chromosome, particularly three copies of the 21st chromosome, is the most common cause of Down syndrome.
  • Short physical stature, typical structural abnormalities in the face and the head, retardation of physical, mental and intellectual development, are the common symptoms of babies with down syndrome.
  • The typical physical abnormalities in the newborn often lead to diagnosis, which is confirmed by a blood test to detect the extra chromosome 21in the infant.
  • In most cases, children who have Down syndrome reach adulthood.

Normally, one copy each of every chromosome is received from the father and the mother to make up the genetic configuration of the infant. Having an extra chromosome, which results in three copies of the same chromosome, is referred to as trisomy. Among the different types, the most commonly occurring trisomy is Trisomy 21, which is the usual reason for Down syndrome, accounting for almost 95 % of cases. In most cases, two out of the three copies of the 21st chromosome may have come from the father. But, mothers older than 35 years are highly prone to contribute this extra chromosome to the infant. However, since most of the births take place in women of a younger age, infants born with this condition to mothers 35 and older, account for only 20 percent of the overall statistics. Mothers with Down syndrome typically have 50 percent probability of giving birth to an infant with the same condition. But spontaneous abortion of fetuses with this abnormality is very common. On the other hand, men who have Trisomy 21 are generally not fertile.

Symptoms

Delayed mental, as well as physical development is a characteristic symptom of babies with Down syndrome. As infants, they are usually quiet, and cry very rarely. Their limp muscles and quiet nature cause them to be described as passive and placid babies. The head is usually small, with a flat and broad face and characteristic slanting eyes. The nose is short; ears are also small and rounded, often situated lower in the head than normal. A large tongue, extra skin folds at the back of the neck, and short but broad hands having only one crease running across the palm, are typical. Hands have short fingers, with the little finger curved inward and often having only two sections instead of the normal three. There is extra space separating the first and second toes. Short stature is also typical of children as well as adults who have Down syndrome. In some cases, these typical abnormalities may not be apparent in the newborns, but they develop gradually.

The average IQ or intelligence quotient of children having Down syndrome is around 50. It may vary greatly between individuals, but still, it may be significantly lower when compared to the average IQ of normal children which is around 100. The listening skills of children who have Down syndrome is usually lower too, which affect the development of language skills. However, visual motor skills are comparatively better, which may make them good at drawing. Attention deficit disorder is common in these children, sometimes along with hyperactivity. Children who have severe intellectual impairment may display autistic behavior patterns. In adults, as well as in children, depression is commonly encountered. Educational and social support, provided early in life, may significantly improve the life and functioning of those who have Down syndrome.

Many heart defects are usually present in babies with Down syndrome. Due to recurrent ear infections and resultant fluid accumulation in the inner ear, they may develop a condition termed serous otitis, which cause hearing difficulties in them. They are at higher risk of developing problems with their vision too, due to the defects in their lenses and corneas. Their neck joints are often unstable, and it may lead to complications such as weakness or even paralysis. Heart disease and thyroid disease may develop in some individuals.  Higher risk of blood cancer, or leukemia, is often a cause for the higher mortality rate in children with Down syndrome.

Diagnosis

An ultrasound scan taken during the latter part of pregnancy usually detects the defects associated with Down syndrome. It can be detected much early in pregnancy by a blood test which may show higher levels of certain proteins in the pregnant mother’s blood. This test can be conducted in the initial fifteen to sixteen weeks. Though pregnancy after 35 years of age is known to carry a higher risk of Down syndrome, they account for only twenty out of hundred cases. Hence, all pregnant women, irrespective of their age, are advised to undergo screening for this condition before they reach the 20th week of pregnancy.

Babies with Down syndrome have the characteristic physical appearance which leads to immediate diagnosis of the condition. It can be confirmed by testing a sample of the newborn’s blood to detect abnormalities of the chromosome 21 such as trisomy 21. On confirming the diagnosis, further investigations with ultrasound scans and other specialized blood tests are conducted to determine the extent of abnormalities which may occur as a result of this chromosomal aberration. Detecting associated abnormalities early and treating them appropriately can prevent further deterioration of health. Periodic screening of children with Down syndrome, for the development of thyroid disease as well as hearing and vision problems, is necessary. Instability of the neck joints should be assessed by x-ray analysis before they can be trained in sports to participate in events such as Special Olympics.

Prognosis

Babies with Down syndrome usually have a faster rate of aging, but most of them reach adulthood. The average lifespan of people with Down syndrome is found to be around 49 years, but many live beyond that and even up to 60 years or more. Many complications like memory loss, cognitive impairment and changes in personality, usually associated with aging-related ailments such as Alzheimer’s, begin to appear earlier in life than they normally appear in the general population. Majority of the children who do not survive into adulthood usually die of leukemia or heart disease. Most defects of the heart can be treated with medication or corrective surgery for a better outcome.

In some recent studies, whites who have Down syndrome are found to live longer than blacks who have the same condition. More than genetic disposition, these findings may point to the fact that, better medical care, as well as social, and educational support, can significantly improve the life span of people with Down syndrome.

Watch This !! What is Down Syndrome? The Facts and Myths Explained

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Yasser Elnahas

MD, PHD, Professor Of CardioVascular Surgery
Dr. Yasser Elnahas, Is an associate Professor of Cardiovascular Surgery. Dr. Elnahas was trained as a fellow At Texas Heart Institute And Mayo Clinic Foundation.Dr. Elnahas is dedicated to educating the general public about different disease conditions and simplifying the medical knowledge in an easy to understand terminology.

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