Down syndrome

Almost 18, to 20,000 babies are born every year in India with Down Syndrome resulting from the extra copy of chromosome 21 from either parent.

Definition

A chromosome abnormality resulting in mental retardation and other abnormalities.

Alternative name
Trisomy 21

Causes, incidences, and risk factors
In most cases, Down syndrome is caused by an extra chromosome 21. Downs children have a widely recognized characteristic appearance. The head may be smaller than normal (microcephaly) and abnormally shaped. Prominent facial features include a flattened nose, protruding tongue, and upward slanting eyes. The inner corner of the eyes may have a rounded fold of skin (epicanthal fold) rather than coming to a point. The hands are short and broad with short fingers and often have a single crease in the palm. Retardation of normal growth and development is typical and most affected children never reach average adult height.

Congenital heart defects are frequently present in these infants. Early mortality is often a result of cardiac abnormalities. Gastrointestinal abnormalities such as esophageal atresia (obstruction of the esophagus) and duodenal atresia (obstruction of the duodenum) are also relatively common. Obstruction of the gastrointestinal tract may require major surgery shortly after birth. Children with Down’s syndrome also have a higher than average incidence of acute lymphocytic leukemia (ALL).

Prevention
Down syndrome can be detected in a fetus in the first few months of pregnancy by examination of the chromosomes obtained by amniocentesis. The parents of a child with Down syndrome are at increased risk for having another child with Down syndrome and should be made aware of amniocentesis. Mothers who become pregnant after age 40 are also at increased risk for having a child with Down syndrome.

Symptoms

decreased muscle tone at birth
sutures - separated
asymmetrical or odd-shaped skull
round head with flat area at the back of the head (occiput)
small skull (microcephaly)
slanting eyes, unusual for ethnic group
small mouth with protruding tongue (see tongue problems)
broad short hands
single crease on the palm
retarded growth and development
delayed mental and social skills (mental retardation)
iris lesion (an abnormality of the colored part of the eye, called Brushfield spots)

Signs and tests

A heart murmur may be revealed by listening to the chest with a stethoscope (auscultation). Characteristic abnormalities are revealed by a physical examination.

Inability at birth to pass a tube from the nose into the stomach may indicate obstruction of the esophagus (esophageal atresia) while early and massive vomiting may indicate obstruction of the duodenum or lower segments of the gastrointestinal tract.

Tests include:

physical exam (diagnosis often suspected and made by examination)
chromosome studies (demonstrates three 21-chromosomes)
X-ray, chest (to determine presence of cardiac abnormalities)
echocardiogram (to determine nature of cardiac abnormality)

ECG
X-ray, gastrointestinal (to determine obstruction if symptoms are suggestive)

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