Strange illness

Question
QUESTION: Hi, Me and my friend both have rats and she called me recently saying that her rat, Haku, was sick. She told me this:
He has a very large growth on the inside of his hind legs, almost the size of a golf ball. It is semi solid and seems to not be unattached. He also has been acting strangely. He very recently bit her and held on until she could pry his mouth off her thumb. He could've done real damage if her fingernail wasn't in the way. He never acting this way before and usually was a very gentle and good pet. Another recent thing was that he seemed to be coughing up a strange brown liquid. She saw him cough it up so it wasn't from his nose or eyes.
I was very confused because I know rats can't vomit, and I wasn't sure if the tumor/abscess could has caused any of this or his personality change. He is pretty old, and is a little overweight but other than that used to be healthy. Please help me figure out what is wrong with him, and if there's anything she can do to help him

ANSWER: Hi Morgan


There isnt anything strange about this at all. He has either an abscess or a tumor on his leg which needs attention right away. How long has the lump been there on his leg?  
He bit her because he isnt feeling well. You were right to assume that the change in personality is from not feeling so hot. He is grumpy from it and rightfully so!

The fluid from his mouth was just porphyrin stained saliva and if the harderian gland is working overtime to produce excessive porphyrin he must be stressed.

Let me know how long the lump has been on his leg and we  can decide if its an abscess and I can tell you the next step.

---------- FOLLOW-UP ----------

QUESTION: Ok, I actually got to go see her rat and the lump on him is very big, much bigger than a golf ball. It's been on there for a while, I'd say a month at the most. but it got big pretty fast, and now hes having trouble walking on the leg where its at because its pushing his leg out to the side and his foot can barely touch ground now. He also is very thin and bony, but she always keeps food in his cage regularly. His breathing is also a bit strange, he's taking big, but quick breaths. His fur feels and looks unhealthy too. But his aggression has seemed to have gone away, he was very calm and gentle when I held him that day.

Answer
Is there a scab on it at all??

It sounds like a tumor to be honest. It can be removed very easily be a skilled vet. The reason for the weight loss is due to the fact that the tumor is vascular and it robs the body of the nutrients that the rat is gaining from food, thus in turn the rat starves slowly and starts to drop weight.  Worse yet, because of the lack of proper nutrition, the rats vital organs are not being sustained and organ failure can occur. This is one of the causes of death in rats that have large vascular tumors.  
I would get him to the vet right off and schedule him for surgery. I would not wait for him to get too weak though, the sooner the better.  If you need a vet please refer to my website and the vet page. There is a link to the AEMV to find a good exotic vet that will remove that tumor in no time!

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

Hope this helps!