Down syndrome
Description
Chromosomal aberration that results in mental retardation, abnormal facial features, and other distinctive physical abnormalities
Commonly associated with heart defects and other congenital disorders
Average IQ between 30 and 50 (some higher)
Occurs in 1 per 800 to 1,000 live births
Maternal age above 35 considered a risk factor for having a child with Down syndrome
Also known as mongolism and trisomy 21 syndrome
Pathophysiology
There are three main types of chromosome abnormalities in Down syndrome:
The vast majority of children with Down syndrome have three copies of chromosome 21 instead of the normal two because of faulty meiosis (nondisjunction) of the ovum or, sometimes, the sperm. Each cell in this individual has 47 chromosomes instead of 46. This is known as trisomy 21.
Three to four percent have translocation Down syndrome where the extra chromosome 21 is attached to another chromosome.
In Mosiac Down syndrome, which is noted in about 1% of Down syndrome infants, some cells have 47 chromosomes and some have 46.
Causes
Deterioration of the oocyte resulting from age or cumulative effects of radiation and viruses
Trisomy 21
Assessment findings
Lethargy and poor feeding (in a neonate)
Slanting, almond-shaped eyes
Small, open mouth, protruding tongue
Single transverse palmar crease
Brushfield’s spots on the iris
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