Technicians, compare your typical physical exam for cats and dogs to mine to see if you’re checking every nook and cranny of your veterinary dermatologic exam.
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One the most challenging things about veterinary dermatology is that a lot of conditions look very similar. That’s because there are only a limited number of reaction patterns in the skin. How are you supposed to tell what’s what?
A dermatologic exam is one part of the puzzle and should include your entire patient from stem to stern:
Other classics for environmental allergies include erythema of interdigital spaces, caudal surfaces of the carpus, axillae, inguinal region and ears. When these areas are inflamed, they create the perfect conditions for secondary bacterial and fungal infections. Performing cytology is necessary for appropriate treatment. Even after 20 years of working in dermatology, I am still surprised by findings on cytology—you can never be sure what’s going on until you examine your samples under the microscope!
Patients with atopy often have secondary infections on the ventrum, while patients with adverse cutaneous food reactions will often have secondary lesions over the dorsum. Food-allergic patients also often have perianal erythema with or without adverse gastrointestinal signs that can include halitosis, burping, borborygmus, flatulence, scooting, anal gland issues, pica, vomiting and abnormal stools (very hard, soft, diarrhea, voluminous, multiple bowel movements per day). Unfortunately, many sensitive patients have a combination of food and environmental allergies.
Are there areas of alopecia? Are there lesions? If these are symmetric, consider an internal disease process such as allergies or immune-mediated, metabolic or endocrine disorders. Asymmetric lesions move your differentials to infections, ectoparasites or neoplasia. Are there any comedones (blackheads)? Comedones are also seen with endocrine disorders as well as vitamin-A-responsive dermatoses, demodicosis and dermatophytosis. They can also be seen in animals that are genetically predisposed, like schnauzers or Mexican hairless.
Are there papules, pustules or epidermal collarettes? All of these are seen with pyoderma but also in immune-mediated skin diseases. Pustules that are a result of a bacterial skin infection usually only span one hair follicle. Larger pustules spanning more than one follicle are seen with immune-mediated disease. Bacterial infections usually affect the trunk and may extend down legs, while immune-mediated diseases will affect the head and paws followed by the trunk. Always check mucocutaneous membranes. If affected, your differentials can include harsher forms of pemphigus with a poorer prognosis.
Hyperkeratosis of footpads and the nasal planum can be seen with distemper, zinc-responsive dermatosis, hepatocutaneous syndrome, pemphigus and lupus. This can also be seen with idiopathic nasodigital hyperkeratosis and hereditary nasal parakeratosis of Labrador retrievers. Breed predilections play a big role in narrowing in on a differential diagnosis as well as age and response to previous treatments.
It's a lot, but if you put all the pieces of the puzzle together (patient signalment, history, physical findings and diagnostics), you can’t go wrong.
Suggested reading
Diagnostic methods. In: Miller W, Griffin C, Campbell K. Muller and Kirk’s Small Animal Dermatology. 7th ed. St. Louis: Elsevier Mosby, 2013.
Differential diagnoses. In: Hnilica K, Patterson A. Small Animal Dermatology: A Color Atlas and Therapeutic Guide. 4th ed. St. Louis: Elsevier Mosby, 2016.
Jennie Tait, AHT, RVT, VTS (Dermatology – Charter Member) works at Yu of Guelph Veterinary Dermatology with locations in Ontario, Canada.
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