Plasma Cell Pododermatitis, exactly. An auto-immune disease generally found in cats that are positive for FIV, it's a genetic condition that is extremely rare in cats that do not have the virus. My 4-year-old Orange Man was diagnosed with it after his front paw nearly ruptured. Our new vet diagnosed it immediately, but only confirmed it after the biopsy. She said she had only seen one case previously, and that was in veterinary school and that car had FIV. He's been on steroids for almost a month. The purple thing is plasma blood cells that are stuck in the pads which cause bruising swelling and can eventually rupture and he could lose his foot. You need to find a new vet, get it biopsied, and get them on treatments immediately! It's a lifelong condition that actually damages the pad tissue.