Have Cat Questions? Ask a Cat Vet Online.
Hello. Thanks for the question.
It does sound like this is something like feline leukemia, FIV or FIP (feline infectious peritonitis). Those can be diagnosed based on bloodwork and viral testing. If this is FIV or Feline Leukemia, it can potentially be managed with antibiotics, steroids and nutritional management.
If this is FIP, then we usually see an elevated blood globulin level and fluid in the abdomen. If that's the case, the disease is 100% fatal. We can use steroids to get some response, but ultimately there is no effective treatment.
Here is some info on FIP:
Let me know if you have any other questions.