What is an autoimmune disease?
Our bodies have an immune system that protects us from foreign invaders that can cause disease and infection. If you have an autoimmune disease, however, your immune system attacks itself by mistake, causing serious illness. The immune cells fail to distinguish the body's normal healthy cells from foreign cells, and thus try to destroy the normal tissues. The cause of this "mistake" is not well understood. Autoimmune disease can affect a single system or multiple body systems. Autoimmune diseases can affect skin, connective tissues, nerves, muscles, the endocrine system (the system that controls hormones and other chemicals), red blood cells, and the digestive system. Dogs and cats with autoimmune diseases should not be vaccinated except under certain circumstances – your veterinarian can discuss this further with you.
What causes autoimmune disease?
"...some theorize that genetics and/or environmental pollutants play a role."
The cause or causes of autoimmune disease are not fully understood, although some theorize that genetics and/or environmental pollutants play a role. Ultraviolet (UV) exposure is thought to be a predisposing or “triggering” cause of autoimmune skin diseases in some dogs. Certain drugs have also been reported as potential triggers for pemphigus foliaceus, a common form of autoimmune skin disease in dogs and cats. Early recognition is extremely important. Left untreated, the complications of autoimmune disease are serious and multiple system involvement is common. This can make diagnosis and treatment very challenging and complicated.
What are some of the common autoimmune skin diseases in dogs?
Autoimmune skin diseases are relatively rare in dogs. Some of the more common forms of autoimmune skin disease include:
Pemphigus is a group of five autoimmune skin diseases characterized by vesicles and bullae (large and small "blisters") in the mouth and at mucocutaneous junctions (the junction between skin and mucosal tissues). Commonly affected areas include the eyelids, lips, nostrils, and anus.
Pemphigus Foliaceus (PF) - The term means "leaf-like pemphigus" and this is the most common immune-mediated skin disease of dogs and cats. Pemphigus foliaceus is rarely found in the mouth or at mucocutaneous junctions. In this form of pemphigus, the patient develops crusts (scabs) and ulcers around the eyes, ears, footpads, groin and bridge of the nose. Breeds more commonly affected included the Chow chow, akita, cocker spaniel, Labrador retriever, dachshund, English bulldog, Finnish spitz, and schipperke. Pemphigus foliaceus usually appears suddenly without a recognized cause. In some cases, however, it may be drug-induced or can be the result of years of chronic skin disease.
Pemphigus vulgaris (PV) - The term means "common pemphigus" and it is the most frequent form of pemphigus in humans. Fluid filled blisters called "vesicles" form in and around the mouth, eyelids, lips, nostrils, anus, prepuce or vulva. These vesicles rupture easily, creating painful ulcers. This condition is rare in dogs.
Pemphigus erythematosus (PE) - The term means "red and inflamed pemphigus" and its most common symptom is redness, crusting, scales and hair loss on the nose. Exposure to ultraviolet light worsens this form of pemphigus. Breed predispositions include the German shepherd dog, collie, and Shetland sheepdog.
Pemphigus vegetans - This form is typified by thick and irregular vegetative lesions or lumps associated with chronic "oozing" and pustules. It is believed to be a more benign form of pemphigus vulgaris. This condition is rare in dogs.
Paraneoplastic pemphigus (PNP) - The least common (considered extremely rare) and most severe type of pemphigus. This condition is associated with the presence of an underlying malignant tumor.
Bullous pemphigoid may sound like a form of pemphigus, but it is actually a different type of autoimmune skin disease. Bullous is the medical term for a large thin-walled sac filled with clear fluid. Usually, the skin is very itchy and large red welts and hives often appear before or during the formation of blisters. Vesicles and ulcers may be found in the mouth, at mucocutaneous junctions, and in the axillae (armpits) and groin. Evaluation of the vesicles is critical to the diagnosis. Because vesicles rupture quickly after formation, the dog must often be hospitalized and examined every two hours until adequate biopsies can be obtained. Bullous pemphigoid resolves spontaneously in many cases. It is considered rare in dogs and cats.
Systemic Lupus Erythematosus
The classic example of a multi-systemic autoimmune disease is systemic lupus erythematosus (SLE), commonly referred to as lupus. Lupus is often called the "great imitator" because it can mimic almost any other disease state. The signs of SLE may be acute (sudden onset) or chronic, and usually they wax and wane. A fluctuating fever that does not respond to antibiotics is one of the classic clinical signs of SLE. Stiffness in the legs or shifting-leg lameness is also frequently reported with SLE. Other clinical signs may include blood abnormalities such as hemolytic anemia, thrombocytopenia (low platelet numbers), leukopenia (a low white blood count), and symmetrical dermatitis, especially over the bridge of the nose (often called a "butterfly lesion"). SLE is considered a more common cause of autoimmune skin disease in dogs and rare in cats. Dogs or cats with SLE should not be vaccinated unless first discussed with your veterinarian. Breeds reported in the literature include Nova Scotia duck tolling retriever, Shetland sheepdog, collie, German shepherd dog, Old English sheepdog, Afghan hound, beagle, Irish setter, and poodle.
Discoid Lupus Erythematosus
Discoid lupus erythematosus (DLE) is another autoimmune skin disease seen in dogs and rarely in cats. Another common name for this condition is "Collie nose," although it can appear in many breeds. DLE is seen more commonly in Collies, Shetland sheep dogs, German shepherds, and Siberian huskies. Exposure to sunlight and UV radiation is thought to be a potential cause or trigger. In most cases, affected dogs lose the pigmentation around the nose, although the skin around the lips, eyes, ears and genitals may be also affected. DLE can transform the surface of the nose from its normal "cobblestone" texture to smooth, flat and shiny. Ulcerated sores may occur. Some dogs find the disease irritating while others do not seem affected by it. DLE may be a non-systemic, less-serious type of systemic lupus erythematosus (SLE). It is considered a relatively benign autoimmune skin disease.
How is autoimmune skin disease diagnosed?
"...a biopsy of the affected skin is needed."
To definitively diagnose autoimmune skin disease, a biopsy of the affected skin is needed. Depending on the location, a skin biopsy may be performed with a local anesthetic. However, if the affected area involves the nose or face, or if the patient is anxious, sedation or general anesthesia may be required. A small round block of skin is removed with an instrument called a punch biopsy. This tissue sample is then sent to a veterinary pathologist to determine the diagnosis.
How is autoimmune skin disease treated?
The general treatment for autoimmune skin disease is immunosuppression. This means that your dog will receive drugs to reduce or attenuate the reaction of the immune system that is causing the disease. For many dogs, treatment with prednisone or dexamethasone will be sufficient. Other dogs require stronger immunosuppressant medications such as azathioprine, chlorambucil or oral cyclosporine. If secondary bacterial infections are present, antibiotics and medicated baths will be used. Your veterinarian will determine the optimal treatment plan for your dog's condition.
What is the prognosis for autoimmune skin disease?
The prognosis for autoimmune skin disease depends on your dog's specific diagnosis and the severity of symptoms.
"This is a potentially life-threatening condition..."
In general, this is a potentially life-threatening condition requiring extensive diagnostic tests and treatments. Autoimmune disease is rarely curable, but is often controllable with the appropriate medication.