Metabolic Bone Disease is a serious condition that causes bone deformities, stunted growth, jaw deformities, and even death.
MBD is the only reason that I know of that your iguana would have a twisted spine.
MBD is due to improper care. Go to http://www.greenigsociety.org/mbd.htm
to learn more about it.
I would bet that your iguana isn't under a UVA/UVB fixture along with its regular heat lamp, and that it probably isn't being fed proper iguana foods. It's probably safe to say that this iggy doesn't get outdoor sunbathing time (if you decide to do that, make sure the iggy cant get away and that it doesnt over heat).
If you've only had it a week, all these problems didn't start with you at all. Your buddy didn't know what he was doing with an iguana AT ALL. Unfortunately for the iguana, this means that because your buddy didn't take the time to do research and follow it, that your new iguana will be deformed (and possibly in pain) for the rest of its life.
I was unaware that twisted spines happened overnight though, so maybe my diagnosis was incorrect. Read more people's opinions for sure.
Fortunatley, if it is MBD, while the effects can not be reversed, they can be stopped from getting worse if you immediately start caring for it properly.
I highly reccomend you visit anapsid.org and read all that you can about iguanas. Buy many BIG books about iguanas. The little ones are hardly worth looking at. Iguanas for Dummies is a good one, as is The Green Iguana Manual.
What is your iguana living in?
What kind of lights do you have for it?
What do you feed it and how often?
What kind of bedding is it on?
How big is it?
How old is it?
Please answer as this may help people "diagnose".
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~Sara~
6.6 ball pythons
1.0 Black-lined plated lizard (Lizzy Butt)
0.1 Burmese Python (Pixil)
4.4 Pet Rats
1.1 Dogs (Ozzie and Mandy)
0.1 Cat (Isis)
0.0.1 Synodontis Catfish (Big Spotty Fish)
0.2 Convict Cichlids