Two unusual cases of facial dermatitis in cats


We are just now determining the best concentration levels to run a skin test for food-storage mites.

After finishing my residency at the University of California-Davis in 1994, I decided to remain on as a clinical instructor for an additional two years prior to starting my dermatology career in private practice. I really didn't know what I was getting into.

Casey is a 6-year-old male neutered indoor domestic short-hair cat that presented with a one-year duration of a mild facial pruritus and two deep focal crusts in the preauricular region.

This 6-year-old domestic short-hair cat presented with one-year duration of a mild facial pruritus and two deep focal crusts in the preauricular region.

The owners felt the lesions appeared first, and then the pruritus followed. There are no other pets in the household, and he does not go to a groomer or kennel.

A steroid injection was administered, and the owner reported it was helpful (but did not eradicate the lesions), yet he continued to flare once the steroid injection wore off. Another veterinarian felt he had a viral dermatitis and started him on antibiotics and oral lysine without success. Finally, a third veterinarian performed skin biopsies that alluded to a "hypersensitivity reaction".

He was administered a steroid injection every two weeks for a total of three injections without a favorable response. A hypoallergenic diet was attempted for six weeks without success. He continued to worsen with more crusts forming on the face to the point where he was becoming anorexic. What further diagnostics would you perform?

  • Skin scrapings

  • Ear smears

  • Fungal culture/Wood's light

  • Impression smear of the crust

  • Complete blood count

  • Serum profile

  • FIV, FeLV testing.

These tests were all performed and returned as negative. The impression smear of the crust yielded degenerative neutrophils with occasional cocci bacteria and eosinophils. Blood work was normal except for a mild neutrophilia.

The cat continues to worsen despite being treated to rule out "allergy" per the biopsy results. What would you do?

This 3-year-old domestic short-hair presented with pruritus of the face and neck. It was nonseasonal and mildly responsive to steroid injections.

Treat to rule out ectoparasites, such as fleas, Cheyletiella, Notoedres? Rebiopsy? Submit the biopsy slide for a second opinion? Refer?

When your course of therapy according to your lab results is not resulting in improvement of the patient, you need to question the results. In this case, a second opinion was obtained by a second cutting of the biopsy tissue, and a different pathologist found Demodex cati mites. Casey then was treated with topical lime sulfur dip applied to the facial lesions every other day, and he continues to improve.

Demodex cati in the cat when generalized might signal an underlying serious disease, such as diabetes, systemic lupus erythematosus, FIV or FeLV infection. Thankfully, Casey's bloodwork was fine except for the mild neutrophilia. Occasionally a cat will present with Demodex cati on ear smears observed under oil immersion, but our patient was negative. With this presentation, in spite of numerous skin scrapings, Demodex cati was not detected perhaps because scrapings of such deep crusts are difficult to perform and read under the microscope. It might have been possible, however, to extract a crust and then check scrapings under the crust, but these areas (once the crust was pulled off) were very painful. It was also a concern that the topical lime sulfur dip might not penetrate these crusts, but it did, and within one to two weeks, he was feeling much better and eating well.

Note the dermatological improvement following a diet without grains.

The lesson to be learned here is that when a case is not making sense despite what you feel are correct laboratory results — recheck what doesn't make sense. As I told the client, in the many years I have been a dermatologist, I have seen few allergic cats present like this. The biopsy said "allergy" but deeper cuttings of the tissue were needed to get the accurate diagnosis.

Case of pruritus

Tracer is a 3-year-old indoor male neutered, domestic short-hair cat, and is the only cat in the household. He recently started with pruritus of the face and neck that is nonseasonal and mildly responsive to steroid injections. He is becoming tolerant to subsequent steroid injections because the owner feels they are no longer effective. He has been treated with a reliable adulticide against fleas, Cheyletiella and Notoedres despite none being found on combings and scrapings.

What would you do next: combings, skin scrapings, trichogram/Wood's light, ear smears, fungal culture, cytology of the lesion(s), hypoallergenic diet?

In spite of scrapings and combings testing negative, they should be rechecked at each appointment. In Tracer's case, they were negative again. A trichogram looking for fungal spores was negative, and so was the Wood's light and fungal culture. Cytology of the lesion yielded primarily eosinophils with occasional neutrophils.

Because of the non-seasonality of the pruritus, the cat was started on a hypoallergenic diet of dry and canned food. The term hypoallergenic means ingredients to which the cat has never been exposed, and that calls for a prescription diet from the veterinary office. There are no reliable over-the-counter allergy diets for cats. (A lamb-and-rice, over-the-counter product does not qualify as a proper hypoallergenic diet.) After four weeks on a dry and canned hypoallergenic diet, the cat improved only mildly. Yet when the owner ran out of the dry food and the cat was fed only canned, he seemed to improve markedly. We recommended a diet of canned hypoallergenic diet only and after two weeks, his lesions had cleared.

We then challenged him with dry hypoallergenic diet, and he again flared. Suspecting he might be allergic to a food-storage mite (Tyrophagus putrescentiae), a skin test helped confirm he was positive for the mite. To reduce expense, we had the owner continue canned-only food without any cereals, grains or cheese. (Fancy Feast fish varieties were fed with vegetable gum as the carbohydrate source, and he continues to do well.)

Food-storage mites can produce serious anaphylactic reactions in people allergic to the mite. For example, if a T. putrescentiae allergic person opens a package of baking mix, they might react with anaphylaxis. Food-storage mite allergy in dogs and cats is a new area of exploration in veterinary dermatology. In pets with a facial pruritus, it might be a good idea to get the animal off all dry or processed cereals, grains or cheese for a month.

Since there are several food-storage mites in existence, we are just now determining the optimum concentration levels to run a skin test. Trial and error with diet might be the quickest way to make a diagnosis. Usually feeding the pet a non-dry diet without the previously mentioned ingredients will elicit a change within 30 days.

I've had patients that seem to have a mite "threshold" effect and can have a few commercial dry treats without flaring, yet some pets will flare with just one.

Again, as always in veterinary dermatology, the detective work marches on. Listening to the client and obtaining a good history are always essential in trying to help these allergic pets.

Dr. Jeromin is a pharmacist and veterinary dermatologist in private practice in Cleveland, Ohio. She is a 1989 graduate of The Ohio State University College of Veterinary Medicine and an adjunct professor at Case Western Reserve University's College of Medicine in Cleveland.

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