i believe i read about this on PBC also. My pomeranian started becoming aggressive towards me and my pit puppy, i thought maybe it was just old age since he was 10. After a few months it became obvious there was something going on with him medically. After several vet visits, medications, and imaging it was determined he most likely had cancer. I had to opt to have him put to sleep. That being said, I would definitely take him in for an evaluation to rule out anything that may be causing him discomfort. Good luck!