Belated Answer

This is another picture of the same cat's feet a month or two later.  I'm not sure if you can truly appreciate how crusted and thickened the toes/feet are. This was present on all four feet. I cannot imagine this would be very comfortable for kitty. I didn't have a second picture of the face/ears but suffice it to say it was much worse and the cat was now clinically not doing well. She was losing weight and not very active. This, despite steroids.

So what is this?

Well, ONLY a biopsy of the affected tissues would tell us but the most likely two differentials, given the lack of response to typical skin medications, the severity of the disease and the progression to affect overall health are:

1. Autoimmune disease

2. Cancer (neoplasia)

We do see cancers that present ONLY as generalized skin disease. It's not as common as other types of cancers in pets. Cutaneous lymphoma is a "more common" one seen in dogs.  

Also, other types of cancer can result in skin disease from the suppression of normal immune system function.

Autoimmune diseases are a group of conditions where the body attacks itself. In this case, the immune system is OVER doing it's job!  These are often treated with high (or immunosuppressive) doses of steroids. This cat didn't respond AT ALL to the steroids. However, there are cases where other, more potent medications are required. These often carry with them more serious side effects, so we would never want to just give them without a confirmed diagnosis.

The owner had declined biopsy from the beginning due to cost and so we will never know. The cat was euthanized the day I took this picture due to her poor and declining quality of life.  She was 5-6 years of age.