Canine skin autoimmune diseases
Spontaneous, nasty lesions
These skin eruptions could be from an autoimmune illness
In an autoimmune disorder, the very cells designed to protect a dog from outside invaders turn rogue and attack the animal’s own body. When the disorder affects the outer epidermis and inner dermis of the skin, these layers can separate and cause painful, blistering lesions.
As the skin layers separate, blisters and pustules may form in the empty spaces. These fragile areas may break down due to erosions, develop crusts from the debris and fluid, and lead to hair loss in the affected areas. Secondary bacterial infections are common.
Severe, recurrent cases of atopic dermatitis are often a suspected cause, predisposing a dog to autoimmune skin problems. Symptoms usually include itching, sneezing, rashes, watery eyes and paw chewing. Unfortunately, by the time your dog is definitively diagnosed, the trigger may be long gone, which can make diagnosing and treating these illnesses tricky.
Viruses trigger autoimmune skin conditions in humans, but haven’t been well documented in dogs. A genetic predisposition, which is known to play a role in human autoimmune disorders, has not been proven in dogs, but it is suspected.
“[For example], superficial pemphigus is recognized more frequently in some breeds like the Akita,” says Dr. William H. Miller Jr., professor emeritus of medicine in the Department of Clinical Sciences.
Certain medications may be the trigger in individual dogs, such as antibiotics like sulfonamide, penicillin and cephalosporin. For some dogs, topical medications used for external parasite control may trigger the reaction. This includes topical ectoparasitic preparations containing fipronil, amitraz, S-methoprene, dinotefuran, pyriproxyfen or permethrin. In these cases, stopping the drug may lead to normal skin. Other dogs require treatment to restore and maintain normal skin.
While autoimmune skin diseases in dogs are not common, they do occur. A thorough history is important to rule out any possible drug-induced conditions. Parasitic conditions should also be eliminated as causes of the skin lesions. If there’s still no answer, a skin biopsy — which is the only way to truly diagnose an autoimmune skin problem — may be required.
This can be complicated. The ideal biopsy should capture a vesicle or pustule before it erodes. Unfortunately, these are very delicate lesions and are rarely found intact in time to do a biopsy. Also, any treatment prior to the biopsy can skew results.
“Even with my 40 years of experience,” says Miller, “I can’t absolutely tell you that your dog has an autoimmune skin disease without the biopsy."
"This can be expensive," he adds. "When money is an issue, as it is in many cases, a veterinarian might offer, ‘Let’s try steroids and see what happens.’ If they don’t work well enough, or the lesions come right back after the steroid is stopped, then we’ll biopsy. The biggest issue with that approach is that steroids can’t be used for 14 to 21 days before the biopsy is taken. Otherwise, the histology will be altered and may lead to an incorrect diagnosis.”
In general, treatment with a combination of medications gives faster results. With lower doses of individual drugs, the chance of deleterious side effects is decreased. Most protocols start with glucocorticoids (steroids such as prednisone) alone or in combination with strong immunosuppressive medications such as azathioprine or cyclosporine (Atopica).
Steroids are inexpensive and easy for owners to give at home, but they do cause side effects when used long- term, starting with increased drinking and urinating, but potentially escalating into problems such as diabetes mellitus, liver disease and Cushing’s disease (iatrogenic hyperadrenocorticism).
Pulse therapy — intermittent administration of large doses — may be advocated with dogs receiving high doses of steroids initially, but then going to periodic dosing as opposed to lower dosages daily. For mild or localized problems, topical steroids or immunomodulators (drugs that help calm the immune system), such as tacrolimus, may be sufficient to hold the disease in remission, at least for a while.
Some dogs will need antibiotics to deal with secondary bacterial infections that thrive in the disrupted skin. Culture and sensitivity to determine the best antibiotic choice is recommended. Dogs with atopy or other allergic dermatitis conditions benefit from having that problem treated concurrently. The same is true for secondary yeast or fungal infections.
Newer areas being explored to treat canine autoimmune skin disease include acupuncture, especially if combined with the use of herbs such as such as radix Curcuma wenyujin, Tripterygium wilfordii, Artemisia annua and Berberis vulgaris.
Oclacitinib (Apoquel) appears helpful, but more study is required before widespread usage will be recommended. A benefit of oclacitinib is that, in general, side effects are less significant and safety is higher overall than long term corticosteroids.
Some dogs will go into remission for variable amounts of time and can be weaned to low levels of medication, or even go off medication for a while. In most instances, the disease will recur.
Finally, while it can be tempting to shampoo your dog, it’s best to hold off.
“Shampoos have several problems. First, the commercially available ones contain 1% hydrocortisone, which isn’t very potent,” says Miller. “The second issue with shampoos is that they can make things worse by the mechanical action needed to apply them and rinse them off. Autoimmune skin is more fragile than normal, and rubbing and rinsing can make it worse.”
Types of canine skin autoimmune diseases
This article has been reprinted with permission from the Cornell University College of Veterinary Medicine’s DogWatch newsletter, published by Belvoir Media Group. When you become a member of the Riney Canine Health Center, you will receive a free subscription to DogWatch.