Severe skin problem on 12y male cat

Hello everyone! Meet our 12 year old male cat. His name is Mister Cat. This was him a couple of years ago: https://ibb.co/album/G31X8K. Mr. Cat is having a bad year, or bad 1.5 years. I'll try to break his current medical state and what we did so far down as sistematically as possible. - February of 2021: In February of 2021 I noticed pockets of fur laying around the house. When he was cleaning/licking his belly, parts of the fur were stripped away and skin without fur was left behind. The furless patch was small and it took months(to the July) to get to the size around 7x7cm. I also noticed that he had dirty ears. - April 2021: This is the image in April 2021. Notice that there is no sign of any skin problems (apart on the belly, which I don't have an image of). https://ibb.co/album/9Zgc5W - July 2021 In july he first visited the vet.The vet tested for Microsporum canis and gave an insecticide. Results were negative and cat's condition did not improve. He received a different insecticide a month and half later and we waited for improvment in vain. - November 2021 In November he received the third type of insecticide and the condition only got worse. This is an image from November before he received the third type of insecticide. https://ibb.co/album/1znL57 - December 2021 This is an image from December. It was very evident that insecticide caused additional skin problems. In December he was again tested for Microsporum and fungal diseases and did blood tests works which returned normal. This are the blood work results. https://ibb.co/album/k2kwBZ T4 was tested again at 3rd party due to the vets machine malfunctioning. The final results for T4 were normal too. https://ibb.co/album/NZ54Ln - February 2022 In mid January the results came back and there was evidence of fungal infection. He started receiving Sporanox for 1 month The vet also said that he has bacterial infection of the skin and prescribed a hydrolyzed protein food. He's on it since. He was negatitve for environmental allergens tested: https://ibb.co/album/k2kwBZ He received 3 doses of antibiotic via IV with 2 weeks interval. At the same time we started washing him 2x a week with Plivasept which contains chlorhexidine and later we switched to Malaseb. - March 2022 https://ibb.co/album/9HkWJk This are images from mid march 2022. No visible improvement, I'd say it is even worse. - April 2022 At the star of April we did a biopsy of the skin and tested for Histopathology and microbacterial diseases which only confirmed that he has a bacterial infection and that it is not some antibiotic resistant bacteria causing his problems. In mid April he started receiving a new type of antibiotic called Synulox 2x a day. A week later the he also started receiving a low dose of Prednicortone due to redness on the belly. Giving corticosteroid Prednicortone showed no signs of improvement on his belly so it was tapered off after 10 days. - May 2022 https://ibb.co/album/934xVT This image is after a month of Synulox. It is evident that the condition got a little better on his back and tail. However there is no improvement on the belly on paws. I should mention that he is also getting zinc, salmon oil and biotin supplements since start of may. Other symptoms include frequently closed eyes, very dirty ears, shaking all 4 pawns as if he stepped into the water and cramps in the torso around the area where front paws connect to the body. Take a look at the video of cramps. Both symptoms started with the onset of the disease he is having. Video of cramps: https://filebin.net/qf3slezgtkaemrci This image shows his flaky skin after 1 week without washing: https://ibb.co/album/934xVT It is glaring that the cat has 2 diseases. A bacterial infection which got better with oral antibiotics and something else that is causing bacterial infection. While antibiotics improved the symptoms(bacterial infection), I fear that the future does not look bright if the real cause of his issues is not found. The vet was very professional and caring, even did an ultrasound of the belly, but has admitted that after test for Cushing disease, which is scheduled a month after the last dose of Prednicortone(end of June), he has nothing left to look for. If two heads are better than one then the collective heads of the web must be the best. I seek additional advice on how to manage Mr. Cat's skin problem and what additional tests to do. I appreciate any advice. Best regards, Mitt  

Hi - I can't diagnose your cat but I can put some pieces into your jigsaw of skin disease. First, it sounds as though your cat was showing signs of skin disease from the very first presentation - licking patches of fur and ear disease, both of which are classic signs of a skin allergy or other generalised skin condition.   All ears are, is skin down a hole, that makes wax when it gets stressed.   We always rule fleas out first, by giving something that we know will definitely kill them, and repeating (usually monthly) so that fleas can't live on the cat.  Many skin diseases are allergies and many of these cats are allergic to fleas, so ruling out flea allergy with a 'proper' (flea killing and deterrent) flea product actually solves a large per cent age of these cases.

Unfortunately it is extremely common even for skin allergies to occur out of the blue, and you describe signs of skin allergy right at the start of the case, so I don't accept from your account that the flea product caused the signs.   It seems more likely that the condition simply progressed.

It is not normal that skin infections occur spontaneously in healthy skin - either these cats are immunodeficiency or the skin's protective barrier becomes damaged.  As you suggest in this case, perhaps the itch leads to scratching which leads to infected skin.  In the UK it is common to treat these cases with antibacterial shampoo if cats tolerate it (the skin infection is on the surface of the cat, so it makes sense to imply the antibacterial / anti yeast there).  However, the underlying cause of the scratching is useful to find.

It is not normal for skin infections to occur spontaneously in healthy skin.  Usually, cats with skin infections are either immunodeficient or the skin's protect barrier has become damaged.  As you suggest, perhaps an itch (caused by allergy or fleas or mites or something else) leads to scratching which infects the skin (there are bacteria under cats' nails).  In the UK it is common to treat skin infections with a shampoo rather than tablets (the liquid goes to the site and not round the body).  However, the underlying cause of the scratching is important to find.

I have not looked at the pictures (I'm afraid we cannot offer second opinions here) and it is hard to tell from your account exactly which tests have been done.  Scratching is sometimes a response to pain, so I wonder whether pancreatitis and arthritis have been ruled out.  Cancer can present in all kinds of ways.  However, mites and allergy may also explain what you are describing.  A good question for your vet is 'what is left to rule out?' and another, if they truely have run out of ideas, would be whether you could be referred to a skin or medical specialist.