My iguana has a bump on his back & doesnt move much.

Question
Good morning Hannah.  I am aware that Diane is listed as the expert on iguana's but she is on vacation until the 14th so I am hoping you can help me.  I have an iguana, Fred, (not even sure if he is actually a male, but that's what my son named it) who hasn't been coming out from under his cave type rock for 2days.  He usually lays on his hammock under his heat lamp, but since I moved he hasn't been very active.  This morning I moved his cave rock and noticed a bump on his back of some kind.  What could that be from?  He hasn't been eating much that I am aware of.  When I talk to him he looks at me but doesn't crawl at all.  Please help, as my 10yr old son and I is heart broken. :(

Answer
Do you know how old he is? Has he lost any weight? What is the temp. of his cage? Is the lump oozing at all? Is his food dusted, and does he have a UVB lamp?
Please look at this site:
http://www.anapsid.org/lesions.html
One thing that could be causing a bump along the spine is MBD, a disease that if caught early, can be prevented from spreading. MBD is a bone disease, caused by a number of things including a lack of calcium. If this is the problem, and you take him to a vet, she may be able to help him.
http://exoticpets.about.com/cs/reptilesgeneral/a/metabolicbd.htm'
Once you answer my questions, I will be able to give you more information about whats wrong with the little guy, and hopefully help you get him healthy.
Best wishes,
Hannah