Does FIP cause the lymph nodes in the neck to become swollen? I can't find any info about that on the internet. It just talks about intestinal lymph nodes.
Not usually- the cat is depressed, anorexic, URI set in,lethargic not interested in much- in the wet form pockets of fluid set in either in the chest or the belly. A needle draw will produce yucky smelly yellow thick fluid. On the dry version there is no pocket of fluid. It is always fatal and there is no accurate test to discover it yet today.
If one of my cats were FIP+, I'd bring this question to a group of people whose online focus was strictly the care and management of FIP. There are 2 such online groups that I'm aware of with a combined membership of over 3000 people and a combined history of 21 years experience with this very difficult disease....chances are that someone there will either share your experience, know of someone who has, or know where to look for the answer.