Autoimmune disorders occur when a dog’s own protective cells mistakenly attack its body. When these rogue cells target the skin’s epidermis and dermis, the layers can separate, leading to painful, blistering lesions. These fragile areas may erode, crust over, and cause hair loss, with secondary bacterial infections being a common complication. While the exact triggers are not always clear, severe or recurrent atopic dermatitis can predispose dogs to these issues, manifesting as itching, sneezing, rashes, and paw chewing. Diagnosing autoimmune skin conditions can be challenging, especially since the initial trigger may no longer be present by the time a diagnosis is made.
Understanding the Causes and Triggers
While viruses are known to trigger autoimmune skin conditions in humans, their role in dogs is less documented. Although genetic predisposition is suspected in canine autoimmune disorders, similar to humans, it has not been definitively proven. However, certain breeds appear more susceptible. For instance, superficial pemphigus is recognized more frequently in breeds like the Akita.
In some individual dogs, medications can act as triggers. Antibiotics such as sulfonamide, penicillin, and cephalosporin have been implicated. Similarly, topical medications used for external parasite control, including those containing fipronil, amitraz, S-methoprene, dinotefuran, pyriproxyfen, or permethrin, may provoke a reaction. In such cases, discontinuing the medication might resolve the skin issues, while other dogs require ongoing treatment to maintain healthy skin.
Diagnosis: A Path to Clarity
Although autoimmune skin diseases are not common in dogs, they do occur. A comprehensive medical history is crucial to rule out drug-induced conditions and parasitic causes for the skin lesions. If these are eliminated and the cause remains unclear, a skin biopsy may be necessary for a definitive diagnosis.
Performing an accurate biopsy can be complicated. Ideally, the biopsy should capture a vesicle or pustule before it erodes, but these delicate lesions are rarely intact. Furthermore, any prior treatment can interfere with the biopsy results. As Dr. William H. Miller Jr. notes, even with extensive experience, an autoimmune skin disease diagnosis without a biopsy is not absolute.
Cost can be a significant factor, sometimes leading veterinarians to initially try steroids. If steroids are not sufficiently effective or if the lesions return after stopping the medication, a biopsy may be pursued. However, a critical consideration is that steroids cannot be administered for 14 to 21 days before a biopsy to avoid altering the histology and potentially leading to an incorrect diagnosis.
Treatment Strategies for Autoimmune Skin Disease
Effective treatment often involves a combination of medications to achieve faster results and minimize the risk of side effects from individual drugs used at lower doses. Protocols commonly begin with glucocorticoids (steroids like prednisone), either alone or in conjunction with immunosuppressive medications such as azathioprine or cyclosporine.
While steroids are affordable and easy to administer at home, long-term use can lead to side effects. These can range from increased thirst and urination to more serious conditions like diabetes mellitus, liver disease, and Cushing’s disease. Pulse therapy, involving intermittent administration of high doses, may be employed initially, followed by periodic dosing instead of daily lower doses. For milder or localized issues, topical steroids or immunomodulators like tacrolimus might be sufficient for temporary remission.
Secondary bacterial infections can thrive in compromised skin, necessitating antibiotic treatment. Cultures and sensitivity testing are recommended to identify the most effective antibiotic. If your dog suffers from atopy or other allergic dermatitis conditions, concurrent treatment is beneficial, as is addressing secondary yeast or fungal infections.
Emerging treatments for canine autoimmune skin disease are being explored, including acupuncture, often combined with herbal remedies such as radix Curcuma wenyujin, Tripterygium wilfordii, Artemisia annua, and Berberis vulgaris. Oclacitinib (Apoquel) shows promise, though further study is needed before widespread recommendation. A significant advantage of oclacitinib is its generally lower incidence of side effects and improved safety profile compared to long-term corticosteroids.
Some dogs may achieve remission for varying periods, allowing for weaning to lower medication doses or even temporary discontinuation. However, recurrence is common in most cases. It’s also important to note that while shampooing might seem beneficial, it’s often best to hold off. Shampoos with low concentrations of hydrocortisone may not be potent enough, and the mechanical action of applying and rinsing can exacerbate the fragility of autoimmune-affected skin, potentially making the condition worse.
References:
- Cornell University College of Veterinary Medicine’s DogWatch newsletter.
