SLE in the cat: Clinical signs vary dramatically

A 9-year-old castrated male Persian cat was referred with a four-month history of non-pruritic crusting and alopecia involving the face and abdomen.

Table 1

The cat did not respond to previous treatment with repositol methylprednisolone acetate (20 mg), amoxicillin, cefadroxil and enrofloxacin.

Physical examination revealed no abnormalities other than skin disease. Symmetrical, multifocal alopecia with crusting was present on the face, ears, neck, ventrum and distal limbs. The crusted and alopecic lesions on the face were symmetrical, well-demarcated and arranged in a confluent periocular pattern extending to the dorsal aspect of the head and the dorsum of the muzzle. The medial and lateral surfaces of the pinnae were affected mildly. The planum nasale, peri-oral region and oral cavity were spared. The digital paw pads of all feet were moderately crusted.

Differential diagnoses for these skin lesions included pemphigus foliaceus, systemic lupus erythematosus, discoid lupus erythematosus, dermatophytosis, demodicosis, superficial pyoderma, keratinization disorder, sebaceous adenitis, drug eruption.

A complete blood count (CBC), biochemistry profile, urinalysis, antinuclear antibody test (ANA), dermatophyte culture, deep skin scrapings and multiple skin biopsies were performed. Blood work revealed anemia compatible with chronic disease and thrombocytopenia of 35,000. Skin biopsy specimens taken from the ventral abdomen and face were fixed in 10 percent neutral buffered formalin and revealed interface dermatitis and interface folliculitis (inflammation involving the follicular-dermal interface) comprised primarily of lymphocytes, mast cells and fewer neutrophils. These findings were considered suggestive of lupus erythematosus. Results of the dermatophyte culture were negative.

The cat fulfilled only three criteria established by the ARA for the diagnosis of human SLE (facial dermatitis, thrombo-cytopenia and a positive ANA). Based upon the clinicopathological findings a tentative diagnosis of systemic lupus erythematosus was made.

Prednisone was prescribed at a dosage of 10 mg orally twice daily.

One month after therapy was initiated, the crusting on the face, although still evident, was markedly diminished. In addition, hair was beginning to regrow in previous areas of alopecia. The CBC revealed thrombocytopenia of 75,000. Owing to the presence of persistent thrombocytopenia and only a modest increase in the PCV, chlorambucil therapy was recommended but was refused by the owner. Therefore, prednisone therapy was continued.

Two-hundred and twenty-five days after prednisone therapy was initiated and three months after decreasing the prednisone dosage to 10 mg every other day, the owner stopped administering the prednisone. The cat was returned to the hospital 10 days later when the owner noticed blood oozing from the mouth.

Moderate, multifocal crusting and alopecia were present on previously affected areas and was consistent with a relapse of SLE. In addition, a deep bleeding ulcer, measuring 3x5 mm, was present on the hard palate. Surgical ligation of the palatine artery was required to stop the hemorrhage.

Administration of chlorambucil was again recommended, but the owner declined. Prednisone was re-initiated. Ultimately, clinical remission was maintained again with a dose of 10 mg every other day. The cat has remained clinically normal two years after initial diagnosis receiving the same dosage of prednisone. Adverse effects from corticosteroids have not been evident to date.

Discussion

Systemic lupus erythematosus was diagnosed in this cat based upon the presence of facial dermatitis, anemia, thrombo-cytopenia, positive ANA, oral ulceration and supportive skin histopathology. The cat fulfilled four of 11 ARA criteria that included thrombocytopenia, positive ANA, facial dermatitis and oral ulceration. Although a biopsy of the palatine ulcer was not performed, the ulcer was thought to be attributable to SLE and was considered the fourth ARA criteria for diagnosis of SLE.

The American Rheumatism Association requires a human patient to meet four of 11 criteria to diagnose SLE. The most common findings observed in humans with SLE include malar rash (face), photosensitivity, fever, arthritis, serositis, nephropathy and neurological disease. Some human patients do not meet these established criteria and may ultimately develop additional signs months to years after initial examination.

Our cat fulfilled four of 11 criteria; however, sparse literature exists concerning the diagnosis of feline SLE, making correlation between human SLE and feline SLE difficult.

Cases resembling SLE have been previously reported in cats. Scott described two cats with low ANA titers and skin histology that was supportive of bullous SLE. Both cats achieved clinical remission with high dosages of glucocorticoids. Pedersen and Barlough described 11 cats with clinicopathological findings resembling SLE.

The majority of these cats (eight of 11) responded well to immunosupression. Two of those cats diagnosed with SLE fulfilled four of 11 criteria established by the ARA, including positive ANA, but supportive skin disease was absent. It is interesting to note that in the aforementioned study, the majority of cats diagnosed with SLE were purebred Siamese, Persians or Persian-related breeds.

This article serves to underscore how variable lupus erythematosus may present clinically in the pet, and even though this disease is rare, it is a reasonable differential diagnosis in the cat with symmetrical, non-pruritic dermatitis and cytopenia.

Dr. Vitale received his veterinary degree from Mississippi State University, College of Veterinary Medicine. He completed a residency in veterinary dermatology at the University of California, Davis and is a diplomate of the American College of Veterinary Dermatology. He is a clinical instructor/lecturer at UC-Davis and a staff dermatologist at East Bay Veterinary Specialists (formerly Encina Veterinary Hospital), Bay Area Veterinary Specialists and San Francisco Veterinary Specialists.