QUESTION: "I think my friend has Down’s Syndrome... but she doesn’t agree?"

**Martijn (admin)** on Sat Nov 27, 2010 1:34 pm

Question by ♥:

"I thinky my friend has Down’s Syndrome... but she doesn’t agree?
We are researching this in class and apparently people with chromosomal abnormalities have only one palm crease (simian line or something). my friend only has one as well. plus she was weird shaped eyes. do you think she should get her DNA tested?"

http://radiodownsound.com/2010/11/27/i-thinky-my-friend-has-downs-syndrome-but-she-doesnt-agree

1 - My simple answer for this question is: 'No!'

2 - My longer answer is: 'No, a simian line is no good reason at all to get her DNA tested... but the context should provide a more definite answer!'

Basically, this question perfectly illustrates how easily scientific handreading facts can lead to misleading conclusions when the facts are misunderstood!!

In this case, the 'friend' appears to be a member of a class where chromosomal abnormalities are being discussed (most of these people probably have an IQ above average), so in this context one can easily conclude that it would even be a waiste of time, money and energy to recommend any person with a simian line to get his/her DNA tested.

Because... while simian lines are relatively common in the hands of people with Down's syndrome, THIS DOESN'T IMPLICATE that most people with a simian line should have some kind of genetic disorder!

For example:

In a population of a million people (1.000.000)...

- You will find about 30.000 people who have a (complete) simian line in at least one hand [Notice: the occurence of the simian line is about 3%]; and about 10.000 of them will have it in both hands [Notice: the occurence of the simian line in both hands is about 1%].

- But you will find only about 1.000 people with Down syndrome [Notice: the occurence of Down's syndrome is 1:1000], of which only about 400 will have [Notice: the occurende of the simian line in the hands of people who have Down's syndrome is around: 40%].

CONCLUSION:

In this example, about 31.000 people have a simian line in at least one hand, but the very large majority of these people doesn't have Down syndrome (30.000)! ...Nor do they have any other chromosomal disorder!

PS. Finally, you may now wonder... then how can one differentiate a simian line in Down syndrome from a simian line in a person who doesn't have Down syndrome?

The answer is simple: you will have to consider other characteristics of the hand before one can jump into conclusions... the following article presents an overview of 27 typical hand characteristics in Down's syndrome.

The simian line is only one of those characteristics!!:
http://www.handresearch.com/diagnostics/simian-line-down-syndrome.htm