Our best friends are like us in some ways we might wish they weren't. Like people, they're susceptible to the many diseases that can result when the immune system confuses healthy tissues and organs with enemy invaders. Depending upon the diagnosis and severity of the symptoms, as the first line of defense, veterinarians typically administer drugs that subdue immune function. These drugs, called corticosteroids, can save lives. Dogs taking them have to be closely monitored, since adverse side effects can have devastating consequences.
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What the Immune System Does
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The immune system is like a police force, constantly patrolling a dog's body to make sure no foreign invaders have breached the defenses, writes veterinarian Kathleen R. Hutton in Dog Owner's Guide. When the immune system identifies rogue cells or microbes, it attacks aggressively, deploying white blood cells and antibodies to the site to neutralize any health risk to the dog. But if the immune system loses the capacity to distinguish between local and foreign cells, it may attack the very tissues it exists to protect. Many conditions can result if the immune system malfunctions in this way; collectively, they're known as autoimmune diseases.
Autoimmune Diseases in Dogs
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Some autoimmune diseases target only one organ or type of tissue while others launch wide-ranging attacks throughout the body. Polyarthritis, for example, affects only the joints; hypothyroidism targets only the thyroid gland. Systemic lupus erythematosus, more commonly known as lupus or SLE, can impact many different organs and tissues at the same time, including the skin, joints and red blood cells. Often called the "great imitator," the symptoms of lupus can mimic many other diseases, notes Hutton. Some breeds are more susceptible to specific autoimmune diseases than others, suggesting the existence of genetic risk factors. German shepherds contract both lupus and polyarthritis more often than many other breeds. According to "The Merck Manual of Pet Health," other breeds at increased risk for polyarthritis include Doberman pinschers, retrievers, spaniels, pointers, toy poodles, Yorkshire terriers and Chihuahuas.
Corticosteroids and Autoimmune Diseases
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Standard veterinary protocol for treating most autoimmune diseases in dogs utilizes a class of drugs called corticosteroids. These synthetic drugs are a much stronger version of cortisol, a hormone produced naturally by the adrenal gland. One subclass, glucocorticoids, are most often used to treat dogs, wrote veterinarian and clinical pathologist Randy Kidd in an article for "The Whole Dog Journal." These come in a wide range of brand names, potencies and forms, including tablets, liquids, topical preparations and injectable drugs, but all do two things simultaneously: suppress the immune system and reduce inflammation. Additional treatments depend upon the disease and the severity of the dog's condition. For an autoimmune disease involving the kidneys, for instance, a vet may advise fluid therapy and a low-protein diet. To treat infections contracted as a result of autoimmune disease, she may prescribe antibiotics.
Side Effects and Warnings
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Administering corticosteroids is "always a balancing act" that must weigh the life-saving properties of these drugs against potentially life-threatening adverse side effects, writes Kidd. These drugs inhibit bone formation, calcium absorption and wound healing. Dogs with suppressed immune systems are more vulnerable to infections. Pennsylvania vet Barbara Forney, writing about the frequently prescribed corticosteroids prednisone and prednisolone, says that while the most common side effects include increased thirst, appetite and urination, others can be more serious. Among them: Cushing's disease, which causes the dog's body to overproduce cortisol. Signs include hair loss, a dry coat and a potbellied appearance. Some dogs also may become aggressive on these drugs. In young dogs and pregnant or lactating females, these drugs either should be avoided or used only if the benefits outweigh the risks, Forney advises.
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