Get It Down 31 for 21: Post 11

Thanks Rebecca for the article!

One extra chromosome at the root

By Mark Guydish
Education Reporter

Down syndrome strikes quite literally through the blueprints of life: The chromosomes containing our genetic code. A person normally has 46 chromosomes, 23 from each parent. Down syndrome is caused when a person has three copies of chromosome 21, technically called “trisomy 21.” All the chromosomes are normal, there is just one too many.

There are three variations on this problem, though the outcomes are pretty much the same, according to Lehigh Valley Hospital Pediatrician Dr. Donald Levick. “The vast majority of children with Down syndrome have standard trisomy 21.”

A second variation is “translocation trisomy,” when all the cells have the right number of chromosomes, but “a piece of chromosome 21 attaches to another chromosome, so there is extra chromosome 21 material in the cells This happens in 3 to 4 percent of the cases.”

The third variation is called “Mosaic Down syndrome,” which occurs when some cells have the normal 46 chromosomes while others have the extra one. This also happens in 3 to 4 percent of Down syndrome cases, and can be a bit harder to detect at first because “the physical features may be mild and therefore tougher to pick up at birth.”

Those features include the facial distinctions most people associate with Down syndrome: eyes slanting upward and outward with a fold of skin on the inner side and a narrower slit to the eye. The face appears flatter, the head smaller, the ears lower and the lips thinner.

There are non-facial traits as well, including pinky fingers that turn in slightly and what was once called – with political incorrectness demonstrating how unkindly the world once viewed children with Down syndrome – a “simian crease.” That’s a single crease across the palm rather than the two creases most people see when they open their hands.

The therapy children with Down syndrome are most likely to need is speech, Levick said. In all cases there will be “some degree of delay both in terms of cognitive skills and motor skills, but that’s variable and you can’t predict it at birth.” Still, “there’s no such thing as having a more severe or less severe case of Down syndrome. You either have it or you don’t.

“As with most genetic problems, there is no real known cause,” Levick said, though the risk goes up with the age of the mother. There is also no known cure. “The most promising line of help is aggressive therapy and socialization.” In the decades since society adopted the idea of therapy started near birth and inclusion of students with Down syndrome into regular classrooms, people with Down syndrome have been living longer, more traditional lives, often on their own. Some marry and have children (it is not hereditary). They learn to play musical instruments and dance, they hold jobs and keep house. In short “they are doing remarkable things,” compared to the low expectations foisted on them in decades ago, before Down syndrome was really understood.

And by the way, Levick noted, it’s “Down syndrome,” not “Down’s.” Don’t make the mistake amid parents and advocates can react harshly when you use the latter. “I’ve learned that from personal experience.”

3 Responses

  1. Great article!!

  2. Excellent article! Thank you for posting it as I think some of us have trouble knowing the difference between the different types of Down syndrome. I also applaude Levick’s clarity of Down syndrome opposite Down’s. I am in the group of parents that really despises the incorrect use of the term.

  3. In England it is Down’s syndrome. :o) In America we say Down syndrome.

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