I recently saw a very large, and very friendly bull mastiff that presented with what appeared to be typical interdigital cysts. These had been chronically recurrent and previous histopathology indicated a pyogranulomatous reaction.
However his lesions responded poorly to three weeks’ of cephalexin antibiotic therapy and, in fact, he developed several lesions on his other feet.
Cytology revealed mild bacterial colonisation, and it occurred to me this might be an immune-mediated reaction (his blood work and TSH/T4 were all within normal limits) – and, hey presto, we got a rapid clinical response to steroids.
In spite of being under control he has also developed an acute erythematous otitis externa, so I think a food trial is my next line. Watch this space…