Down syndrome is a genetic condition caused when cell division results in an extra full or partial copy of chromosome 21. The medical term is Trisomy 21 due to the triplicate copy. This extra genetic material causes the developmental delays and physical features associated with Down syndrome. There is no known cause or cure for Down syndrome. Chances of having a baby with the condition are increased with maternal age. However, a majority of babies are born to mothers who are under 35 years of age.

The vast majority of individuals with Down syndrome (approximately 95 percent) have an extra 21 chromosome. Instead of the normal number of 46 chromosomes in each cell, the individual with Down syndrome has 47 chromosomes. The medical term for the condition is called Trisomy 21.

The second type is called translocation Down syndrome since the extra 21 chromosome is attached or translocated on to another chromosome, usually on chromosome 14, 21 or 22. If translocation is found in a child with Down syndrome, it is important to examine the parents’ chromosomes, since in at least one-third of the cases, a parent may be a carrier of the translocation gene. Three to four percent of individuals with Down syndrome have translocation.

Mosaic Down syndrome is noted in about one percent of individuals. In this case, some cells have 47 chromosomes and others have 46 chromosomes. Mosaicism is thought to be the result of a random happenstance in cell division soon after conception.

Children with Down syndrome may be shorter in stature and their physical and cognitive developments may be slower than their typically developing peers. There is a wide variation in cognitive abilities and developmental progress in children with Down syndrome. Also, they meet their developmental milestones more slowly and language development can be delayed. It is important to note that a caring and enriching home environment, early intervention, and inclusive education efforts all have a positive influence on the child’s development.

https://www.cdc.gov/ncbddd/birthdefects/downsyndrome/growth-charts.html

Parents who have a child with Down syndrome have an increased likelihood of having another child with Down syndrome in future pregnancies. It is estimated that the likelihood of having another child is about one in 100 in trisomy 21 and mosaicism. If, however, the child has translocation Down syndrome and if one of the parents is a translocation carrier, then the likelihood of recurrence increases markedly. The actual likelihood depends on the type of translocation and whether the translocation is carried by the father or the mother.

• Individuals with Down syndrome should be followed closely by a physician who should provide general health maintenance, immunizations, attend to medical emergencies and offer support and counseling to the family. There are, however, situations when children with Down syndrome may need special attention.
• 60-80% percent of children with Down syndrome have hearing deficits. Therefore, audiologic assessments at an early age and follow-up hearing tests are indicated. If there is a significant hearing loss, the child should be seen by an ear, nose and throat specialist.
• Forty to 45% of children with Down syndrome have congenital heart disease. Many of these children will have to undergo cardiac surgery and often will benefit from long term monitoring by a cardiologist.
• Intestinal abnormalities also occur at a higher frequency in children with Down syndrome. For example, a blockage of the food pipe (esophagus), small bowel (duodenum) and at the anus are not uncommon in infants with Down syndrome. These may need to be surgically corrected at once in order to have a normal functioning intestinal tract.
• Individuals with Down syndrome may have more vision issues than their typical peers. Vision issues may include smaller tear ducts requiring stints, cataracts, cross-eye (strabismus), near-sightedness, far-sightedness and Kertaconus. With proper exams and treatment, most vision issues can be corrected or accommodated successfully.

The American Academy of Pediatrics published Down Syndrome Healthcare Guidelines to help families and physicians know when, why and how to screen for common medical conditions.

Global Down Syndrome Foundation published Adult Down Syndrome Healthcare Guidelines to ensure adults receive adequate preventative medical care.

Checklist