We had a little chihuahua pup that had an auto-immune disease.  She had a great life for 6 years and then passed away a few months ago due to pancreatitis.
My daughter had a little chihuahua pup that we rescued and she had an autoimmune disease.  We had a rough first year, but then it seemed things were good.
user
So, the pup is healthy and  situated now?
assistant
Well, we made it 6 years and then she got pancreatitis.  She recovered from that but then we noticed her being really sleepy.  Turns out her body had started destroying her red blood cells, we tried for a few weeks to help her, but ultimately there was nothing more we could do.  I still think about her daily.
user
I'm sorry to hear that RIP doggo.   I have a rescue that's middle aged now. 
assistant