If spina bifida can be prevented by taking folic acide, how can it be
characterized as a genetic disorder?

This may be helpful:

http://www.sbaa.org/site/PageServer?pagename=asb_genetics

As we all know many diseases are results of combined effect of genetic
and environmental factors, in this case "spina bifida" the mechanism
of inheritence is not yet fully understood but statistical data
indicate that genetic predisposition is present and some environmental
factors can also play some role such as; heat,season of impregnation
and...
so genetic factors are omly part of story.

The approach to classifying diseases fall into two main categories:
splitters or clumpers.

The splitters attempt to categorize each disease separately while
clumpers place diseases into general categories.

Birth defects, such as spina bifida, can be manifestations due to
insult to cells during fetal development, which can occur in
nutritional deficits, e.g. folic acid deficiency.  Folic acid deficit
causes damage to DNA and then cellular development.  This is a
"genetic defect" but is not inherited.  On the other hand, birth
defects resulting in spina bifida can also be due to the inheritance
of a bad gene.

If one is a splitter, then each cause of spina bifida will have its
own name.  If one is a clumpter, then all causes of spina bifida are
classified as "genetic disorder".

As we learn more in medicine, we will continually re-classify diseases.

Best regards,
Andrew Doan, MD, PhD

<a href="http://www.medrounds.org">MedRounds</a>