Is it possible for someone to have Down Syndrome without displaying any of the typical physical features? The reason I ask is that I was recently given a client’s neuropsychological profile to look over (IQ, psychological workup, academic tests, etc.) and it mentioned that he had a diagnosis of Down Syndrome. I was shocked, as this boy looks completely typical.
So?
Wikipedia:
Emphasis added.
Yes, it’s possible. The most likely explanation is that he has Mosaic Down Syndrome, in which only some of his cells have the extra chromosome. These folks may have a more mild presentation than a person with Down Syndrome.
But it’s also possible for a person with “regular” Down Syndrome to have mild symptoms, or symptoms which don’t include the physical look we associate with Down Syndrome, or to have only some of those physical markers, which you may have not noticed (like a short pinky finger).
That’s interesting, I didn’t know about mosaicism. (I read that whole study. :D)
Actually, I have a follow up question.
Is Down Syndrome typically a death sentence? Can a person with Down Syndrome live to 75?
That’s actually a really complicated question. 75% of fetuses with Down Syndrome won’t make it to birth. Of those that are born, around 88% are still alive at 1 year and 82% at 10 years. Most of these early deaths are due to heart defects.
About 65% of those alive with Down Syndrome at age one are expected to be alive at age 50. And I can’t find any good numbers after that.
Though Down’s Syndrome is also correlated with increased rates of ALL during childhood (Acute lymphoblastic Leukemia), as well as the fact that Alzheimer’s Disease has been shown to be related to Chromosome 21, and thus again Down’s Syndrome presents with major correlations with earlier onset Alzheimer’s Disease(around age 45 onwards).
Those two diseases also really tend to complicate the prognosis of people with Down’s Syndrome, as they are capable of living longer and fuller lives in today’s society, but there are plenty of bumps along the way in having to deal with complications of those diseases that can negatively affect lifespans.
Yes, facial dysmorphicism (sp?) can range the gamut to obvious to " WHAT?!?! They actually HAVE something?"
I actually do have facial dysmorphicism myself. It’s not that obvious, but when I go to conferences for my syndrome there are a bunch of Mini Mes walking around. It’s really kind of freaky…LOL.
I know with improved ways of reading karotypes, they have discovered all sorts of more complicated rearrangements in people previously thought to have simple arrangements.
I wonder if a lot of people with early onset Alzheimer’s might actually have a visable on karyotype mutation on the 21st chromosome. Not exactly Down’s, but more like vaguely related?