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.
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.
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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.
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.
This 3-year-old domestic short-hair presented with pruritus of the face and neck. It was nonseasonal and mildly responsive
to steroid injections.
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The cat continues to worsen despite being treated to rule out "allergy" per the biopsy results. What would you do?
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.
Note the dermatological improvement following a diet without grains.
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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.
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