ACVC 2016: Feline Skin Syndromes - The Frustrating Feline Triad & More
Beth Thompson, VMD
At the Atlantic Coast Veterinary Conference, Valerie Fadok, DVM, PhD, Diplomate ACVD, discussed treatment for feline skin syndromes.
At the 2016 Atlantic Coast Veterinary Conference, Valerie Fadok, DVM, PhD, Diplomate ACVD, gave voice to what all veterinarians are thinking: funding for cat disease research is lacking. As a world-renowned veterinary dermatologist, her lecture focused on common skin syndromes in cats. Syndromes are not diseases, but a collection of clinical signs that have a variety of underlying causes. Getting to the underlying cause is the key to successful treatment.
Hair Pulling and Over-grooming
If the alopecic areas have short stubbly hair, it’s self-inflicted. By plucking hairs from those sites, veterinarians can take a closer look at the broken hair microscopically and confirm this.
In a past study, Stephen E. Waisglass, DVM, a veterinary dermatologist, and Gary M. Landsberg, DVM, DACVB, a veterinary behaviorist, reported on 21 cats with self-induced alopecia. Only two cats studied (10%) were found to have true psychogenic alopecia with no underlying medical cause. The rest had flea allergy, food allergy, atopy, or infectious inflammatory skin disease. The key takeaway from the study is that psychogenic alopecia is a diagnosis of exclusion. With proof that the majority of these patients have an underlying medical condition, veterinarians should put psychogenic alopecia lower on the differential list, unless the owner reports the occurrence of a definitive known stress trigger, such as a new puppy, new cat, a move, or a new baby, among others.
Flea allergy and Demodex gatoi are the two major causes of self-induced feline alopecia. Veterinarians should flea comb these patients and institute rigorous flea control. In addition, veterinarians should skin scrape for D. gatoi, but keep in mind that, like dogs with scabies, negative skin scrapings do not necessarily rule out infection. D. gatoi is thought to be contagious; therefore, asymptomatic housemates should also be skin scraped for mites. Since eggs can show up in feces, a fecal exam is also recommended. Clues that indicate that the diagnosis might be D. gatoi, are sudden onset with poor response to steroids, and a recent history of exposure to a new cat.
After ruling out ectoparasites, veterinarians should consider allergic dermatitis caused by food allergy, atopy, or both. In Dr. Fadok’s experience, food triggers are more common than complete allergy. Dr. Fadok recommends looking for a history that confirms that the problem is not seasonal. In addition, she thinks that it’s important to ask if the pet has a history of gastrointestinal disease or diagnose of IBD. Food trials are useful but challenging in cats. Dr. Fadok shared that in her practice, she has sent owners home with small samples of acceptable foods and let the cat pick the one it would eat. If food is involved, results should be seen within 8 weeks.
Either serum allergy or intradermal skin testing are used to select atopic immunotherapy. Although there is little evidence to support their efficacy, Dr. Fadok has had many cases that respond well. Since it is difficult to do a good intradermal test and feline skin is naturally not very reactive, even dermatologists sometimes prefer serum testing.
The possibility of dermatophytosis should also be considered. Veterinarians should use both a Wood’s lamp and a fungal culture in suspicious cases, although both may be negative in infected cats. For better fungal cultures, the Mackenzie toothbrush technique reduces sampling error. However, Didier Noël Carlotti, Doct-Vét, Dip ECVDAquivet, and colleagues recently reported excellent results with easier-to-use small squares of Swiffer electrostatic cleaning pads. Finally, veterinarians should consider pain as a possible cause. For example, a cat with caudal abdominal self-induced alopecia could have an undetected urinary tract infection.
Miliary dermatitis is a common nonspecific lesion in most cats; nothing about the reaction patterns indicates the underlying cause. As with hair pulling, think flea allergy, atopy, and food allergy. Based on statistics, Dr. Fadok thinks ruling out flea allergy first is essential. Besides allergy, other possible causes are bacterial folliculitis, dermatophytic folliculitis, cheyletiellosis and even mild pemphigus foliaceus. Bacterial folliculitis is more common in dogs and Dr. Fadok doesn’t feel antibiotics should be used unless cytological proof of bacteria is present. If yeast infection is suspected, a thorough examination of the nail beds can be very useful. Many cases have a brownish discoloration around the proximal claw. Veterinarians should scrape the material with a dull #10 blade and examine the cytology. In some cases, taking skin biopsies early on can help rule out allergic disease and could end up saving time and money.
Eosinophilic Granuloma Complex
This triad of indolent ulcer, eosinophilic plaque, and linear granuloma/eosinophilic granuloma can be idiopathic but is more often associated with underlying allergies. Dr. Fadok’s approach to these three manifestations is similar to her approach to military dermatitis and hair pulling— assume flea allergy. Dr. Fadok has seen cases where the lesions resolved when fleas were entirely removed; she suggests checking cytology for bacteria, as cases with underlying bacterial infections can respond to antibiotic therapy.
Eosinophilic plaques appear in multiple forms: linear, infiltrative (fat lip or chin), feet, and oral forms (most severe). Dr. Fadok has also seen a few cats with eosinophilic plaques on the feet that resolved with a change of litter type. Some kittens develop either indolent ulcers or eosinophilic granulomas that are transient. In those cases, aggressive diagnostics and treatment may not be necessary. Another infrequent presentation is mosquito bite hypersensitivity, which can be seen primarily in indoor/outdoor cats; often found on the nose, ears, and toes, it can be diagnosed with a biopsy. With no mosquito repellents recommended for use with cats, Dr. Fadok’s tip to helping these patients is a Soresto collar and steroid therapy.
Feline Idiopathic Ulcerative Dermatosis
Feline idiopathic ulcerative dermatosis is a frustrating syndrome with several possible causes. It presents as a very pruritic ulceration between the shoulder blades and is usually associated with crusting. Injection site reactions have been theorized to be the cause but not all affected cats have a history of interscapular injections. Dr. Fadok looks first at cytology to check for bacterial cocci. Some patients respond well to anti-Staphylococcal antibiotics, topical silver sufadiazine, and protective clothing, such as a tee shirt or a onesie to prevent self-mutilation. If the cytology shows eosinophils, veterinarians should pursue the underlying allergic cause. These cats respond well to steroids or cyclosporine. Gabapentin has been effective in some difficult cases and some experts recommend surgical removal of the lesion, if possible.
Intense Facial Pruritus
Intense facial pruritus can be seen on its own or together with hair pulling, miliary dermatitis, or eosinophilic granuloma on other body parts. It may be an indicator of food allergy; therefore, Dr. Fadok advocates a strict dietary trial as an early diagnostic test after flea control. These cats may respond to oral steroid or cyclosporine, as well. It is important to check cytology for bacteria and yeast and to keep in mind the possibility of a methicillin-resistant Staphylococcal infection. If there is a history of previous antibiotic therapy, a culture and sensitivity is recommended.
Idiopathic Facial Dermatitis of the Persian and Himalayan Cat
When it comes to idiopathic facial dermatitis, also called ‘dirty face syndrome,’ patients develop blackish waxy crusts that stick to the hair around the facial folds. Erythema and alopecia can be seen as it progresses and these cats can be very pruritic. Sometimes, the lesions spread to the entire face and can be found on other parts of the body, as well. Some cats even develop concurrent submandibular lymphadenopathy. Treatment usually involves systemic antibiotics and antifungal drugs, in conjunction with gentle topical therapy (Douxo pads work well for cleaning).
Dr. Fadok pointed out that there are many unanswered questions surrounding these syndromes in cats, but there are many things that veterinarians can do to treat both the clinical signs and underlying causes. Until more research is conducted, there is no way to immediately hone in on what will work best, but a systematic approach to these patients often yields rewarding results.