Rats back is purple

Question
I have a rat, who I have had for nearly a week now. She is fairly small and young (don't know her age). Ever since we got her, she has been sneezing a lot. I read quite a bit around the internet about how sneezing in rats can be a bad thing, but she seems to be otherwise quite happy, so I have not made a big deal of it.

I've noticed lately that the markings on her fur have been becoming more pronounced in colour. I figured this was part of her growing up. But she has now developed a big purple mark on her back, in addition to the brown blotch she has lower down her back. I am worried about this. Her behavior doesn't seem to have changed at all. she still sneezes a lot, but she is eating and going to the bathroom regularly. When I take her out she gets all excited, and can't stop running around sniffing out everything around her. It doesn't seem to me that her breathing has changed at all, either.

So is this purple patch something indicating the need for immediate veterinary attention, or is it just how her fur is colouring?

Also, I do not know if it will be relevant to the situation, but when we got her, the store clerk said she suspects she might be a part Rex rat. So far I haven't seen any curls in her coat, but perhaps I don't know exactly what to look for to confirm or deny this claim.

Your help will be greatly appreciated. I am a first time owner, and am very worried for the health of my rat.

Answer
You are right, the dark spots/black spots are simply the pigments of her skin where the darker fur is going to come in at or possibly was grown in and has thinned or fallen out.  I have seen this alot in the clinic and also with my own rats.  With a rex, this is also common too.  It does make us worry thinking they have some huge bruise or other problem but you were right the first time, its pigmentation.


As for sneezing, its not always bad.  New rats have alot to get used to and if she was kept on pine or cedar, she may be clearing her nasal passages too.   If this gets worse or she seems ill she should see a vet, but right now, normal sneezing for a new rat is what it sounds like.   Everyone sneezes but we are a bit paranoid about mycoplasmosis so this is why some sites say no sneezing is acceptable

Check out my website for more info:

http://www.freewebs.com/crittercity/mycoplasmosispage.htm