The Vet called a few minutes ago. It seems Dante has Polymyositis, without doing further testing, which of course would give us a definitive answer. :(
Harry is at work, so when he gets home, we will have to talk about the options the Vet mentioned to me.
ETA: Isabella knows there’s something amiss, too. She’s been weird around him. We’ve talked on and off since Januaryish about getting another cat. I know I want a female orange tabby kitten (it’s seriously been about 20 years, if not more, since I’ve had a kitten). Her name will be Clementine. When we get another one, I don’t know. If the Fuzzy Dude needs to be on meds for the rest of his life (he’s 12ish), I would rather wait awhile.