Dermatology Challenge: Self-mutilation and over-grooming in a Siamese cat

A 2-year-old intact male Siamese cat was presented to the University of Wisconsin School of Veterinary Medicine's Dermatology Service for evaluation of self-mutilation and psychogenic licking of the forelimbs and abdomen. The owner reported that the problem had started shortly after she had gotten married and moved into her husband's apartment a year ago. The owner also said that the cat was emotional and bonded to her, which the cat expressed by grooming excessively in the husband's apartment and inappropriately urinating on the husband's dirty laundry. Before the move, the cat had lived in an old apartment building in the city. The only differences between the two apartments were that the old apartment had radiator heat and the new one had forced air heat and that the cat was now living with two other cats and a dog. The owner did not report any overt aggressive behavior among the animals or hiding on the patient's part. The owner had sought help from previous veterinarians for the behavior problems. Previous therapies included paroxetine hydrochloride (1 mg/kg once a day) for three months and feline pheromones (Feliway—Ceva Santé Animale) for one month, to which no responses had been noted; the cat had continued to over-groom. The cat had not received glucocorticoids before presentation, and it was not reported to have vomited hair or to have been constipated. All of the animals in the household were receiving a monthly spot-on for flea control, and none of them were reported to have any skin disease.

Clinical signs and differential diagnoses

The physical and dermatologic examinations revealed bilaterally symmetrical areas of matted hair and exudative eroded skin on the distal extremities and noninflammatory hair loss on the ventral abdomen (Figures 1 & 2).

1. The skin of the cats distal forelimb. Note the area of hair loss, erythema, and erosion indicating self-utilation. 2. The cats ventral abdomen. Note the hair loss.

It was difficult to determine whether the cat was over-grooming because of behavior problems or experiencing pruritus resulting in over-grooming. The fact that the clinical signs appeared after the cat moved into a new home and joined an established group of animals suggested that the problem was purely behavioral. However, pruritic cats often present with over-grooming as an owner complaint. The three major causes of pruritus in cats are parasites, allergies, and infections. Psychogenic skin diseases are rare and difficult to diagnose. So it was necessary to consider pruritus as the primary problem to work up.

Flea, lice, and Cheyletiella species infestations were unlikely because none of the other animals had clinical signs and all of them were receiving flea preventives monthly. And because the cat had been receiving prophylactic flea control before the onset of clinical signs and continued receiving it throughout the diagnostic period, flea allergy dermatitis was considered unlikely. Also, flea allergy dermatitis may have accounted for the hair loss on the abdomen but would not have explained the lesions on the forelimbs. Demodex gatoi infestation was a possible differential diagnosis even though the other cats appeared normal. Dermatophytosis and bacterial and yeast infections were additional differential diagnoses. Atopic dermatitis and food allergy were also considered as possible underlying triggers. The differential diagnoses for the inappropriate urination included cystitis, bladder stones, feline lower urinary tract disease, and behavioral causes.

Diagnostic testing

The results of a flea combing were negative for fleas and Cheyletiella species mites. The results of a complete blood count were normal. Impression smears of the lesions on the forelimb revealed neutrophils with intracellular cocci and eosinophils, and impression smears of the ventral abdomen revealed large numbers of shed keratinocytes but no infectious agents. A dermatophyte culture revealed no pathogen growth 21 days later. The owner declined skin scrapings because the results of numerous previous skin scrapings had been negative. Negative results from a skin scraping do not rule out feline demodicosis because demodectic mites can be difficult to find.

Histologic examination of skin biopsy samples obtained from the lesion on the forelimb and the ventral abdomen revealed perivascular eosinophilic dermatosis. Special stains did not reveal any pathogens. These findings were suggestive of an allergic skin disease. A urine sample obtained by cystocentesis for analysis and culture yielded Escherichia coli that was sensitive to all antibiotics tested.

Diagnosis and treatment

The working diagnosis was E. coli bacterial cystitis and allergic dermatitis (atopy or food allergy) with a secondary bacterial infection. Fourteen days of cephalexin therapy (30 mg/kg orally b.i.d.) resolved the cat's urinary tract infection (based on a negative urine culture result and resolution of clinical signs) and forelimb lesions. The cat's inappropriate urination also resolved. The cat's over-grooming decreased but did not completely resolve. Excessive licking of the abdomen has anecdotally been associated with cystitis. But if cystitis had caused the over-grooming, then the over-grooming should have resolved with the successful antibiotic therapy. The lack of complete response to antibiotic therapy indicated that an underlying pruritic trigger was still present.

Because the cat was receiving a flea preventive routinely and had negative flea combing results, food allergy and feline atopy were the top differential diagnoses. So an elimination diet trial was initiated, and all the cats were fed a novel protein diet (Prescription Diet Feline z/d—Hill's Pet Nutrition) for eight weeks. During the first six weeks of the food trial, the affected cat received oral fexofenadine hydrochloride (Allegra—Aventis; 2 mg/kg b.i.d.). The cat stopped licking while receiving this antihistamine; however, when the drug was discontinued during the last two weeks of the food trial, the licking returned, and signs of alopecia were beginning to recur.

Table 1 : In Vitro Allergy Test Results*

Serum was submitted for an in vitro allergy test with various weeds, trees, grasses, fungi, and environmental elements as possible allergens. Only the environmental allergens scored above 150 and were considered abnormal (Table 1). Feline atopy was diagnosed. The cat was successfully treated with immunotherapy for house dust mite allergy; its over-grooming and self-mutilation ceased (Figure 3). The benefits from immunotherapy were evident by six months of treatment. In some cases, it can take up to 12 months for a complete response to immunotherapy. The cat also required fexofenadine twice a year for one to three weeks to treat pruritic outbreaks.

Figure 3 : The cat's abdomen two years after immunotherapy treatment.

Discussion

One of the most frustrating problems in feline dermatology is determining whether a cat presented for evaluation of self-mutilation and over-grooming has a behavior problem or a true dermatologic problem.1-3 This case was seen as a second opinion, and it was useful to know that previous behavior therapies, including pheromone and paroxetine therapy, had not worked. It has been my experience that pheromone therapy is often useful in homes in which cats are aggressive, particularly if the pheromone is sprayed in the home before the new cat is added. Paroxetine, a specific serotonin reuptake inhibitor, has been helpful in cases of feline aggression, over-grooming, and inappropriate urination, in my experience. But in this case, the drug was ineffective in treating both the over-grooming and the inappropriate urination. This information was helpful in convincing the owner that the cat's problem was likely pruritic and not behavioral. It is interesting that the cat had not received glucocorticoids before referral. Glucocorticoid responsiveness is often held as the big clue that a skin disease is pruritic and probably caused by allergies. The problem is that while glucocorticoids are antipruritic, they can also be mood-modifying, most noticeably in cats. A response to glucocorticoids in a cat with symmetrical alopecia does not always indicate a pruritic cause.

In this case, a urinary tract infection caused the inappropriate urination. Simple diagnostic tests (flea control, skin scrapings, flea combings, lack of evidence of contagion) rapidly ruled out parasitic causes of pruritus. A dermatophyte culture was indicated even though other cats were unaffected. Dermatophytosis can present with a wide range of clinical signs and mimic many diseases, so a dermatophyte culture is always cost-effective, especially when more expensive diagnostic tests (e.g. food trials, allergy testing, skin biopsy) are being considered. Rarely is blood work helpful in diagnosing routine skin diseases; however, in cats with flea allergy dermatitis, elevated eosinophil counts may signal a flea or parasite infestation. One investigator found that flea allergy dermatitis was most common in cats with symmetrical alopecia and an elevated eosinophil count.4 Keep in mind that this test is not valid if the cat has recently received glucocorticoids. Skin biopsy was performed in this cat primarily to look for eosinophils in the skin; their presence was helpful in building a case for allergic skin disease. However, a lack of an eosinophilic dermatitis does not eliminate allergies as a cause of over-grooming.

In this case, the cat's over-grooming was caused by year-round pruritus, and the most likely trigger was an allergic reaction to house dust mites. By their nature, cats tend to rest and relax in areas often heavily contaminated with dust (e.g. under beds, in closets). The cat responded well to immunotherapy; in addition, a marked increase in pruritus was noted when the immunotherapy was discontinued. The cat was asymptomatic in its first home probably because the cat was less than 1 year of age and the home was heated by radiant heat. In the second home, the cat was a little older and the home had forced air heat. It has been my experience that animals with house dust mite allergies are more symptomatic in homes with forced air heat than in those heated by radiant heat. Furthermore, the cat required short-term fexofenadine to treat pruritic outbreaks. These episodes occurred during the first week that the air conditioning or heat was used. Dust and debris collect in the air return vents when they are not used and are blown into the house when the heat or air conditioning is first turned on. It is possible that this dust and debris contain high concentrations of house dust mites.

REFERENCES

1. Scott DW, Miller WH, Griffin CE. Muller and Kirk's small animal dermatology. 6th ed. Philadelphia, Pa: WB Saunders, 2001.

2. Mueller RS, Jackson H. Atopy and adverse food reaction. In: Foster A, Foil C, eds. BSAVA manual of small animal dermatology. 2nd ed. Gloucester, England: British Small Animal Veterinary Association, 2003;125-136.

3. Roosje P, Henfrey J. An approach to alopecia in the cat. In: Foster A, Foil C, eds. BSAVA manual of small animal dermatology. 2nd ed. Gloucester, England: British Small Animal Veterinary Association, 2003;71-76.

4. Thoday KL. Aspects of feline symmetrical alopecia. In: von Tscharner C, Halliwell REW, eds. Advances in veterinary dermatology. Vol 1. London, England: Baillière Tindall, 1990;47-69.

The photographs and information for this case were provided by Karen A. Moriello, DVM, DACVD, Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53706.