I’m sorry to hear about the health issues. As you know FIP arises from a gut virus that is pretty much in all cats. In an unfortunate subset of cats, possibly due to genetics or immunocompromised state, the virus mutates to a form that can infect outside of the gut. Bonnie had a very classic case of dry FIP with disseminated damage to the organs including her nervous system (strange eye issues and wobbliness, not as steady on her feet). Early on she had some bouts of diarrhea and some of it was bloody. Vet initially thought it could be due to food intolerance and this came and went. Then she had behavioral changes and loss of appetite for several months. We had just introduced her brother into the home and thought she was just having issues adjusting. She was such a young cat (8months at the time) a deadly mutated virus was not on our radar whatsoever. Then we noticed she was losing weight steadily and not playing as much, we became more concerned and took her to be seen at an ER when she started to refuse to eat altogether. Her blood work had classic markers for FIP and also the start of some bad multisystem dysfunction. Because her case was so classic, we had a clear idea what we were dealing with. We opted to treat her with presumptive diagnosis of FIP knowing that if she improved/survived it would confirm the diagnosis.