Discoid lupus erythematosus is considered a benign form of systemic lupus, a form of autoimmune disease. Autoimmune diseases are those in which the immune system starts attacking normal components of the body producing antibodies against itself. The exact reason for which autoimmune diseases develop is unknown, but it is hypothesized that genetics play an important role.
Discoid lupus is limited to the skin and can affect both people and dogs. In dogs, the face and in particular the nose are commonly affected areas, and direct sun exposure seems to aggravate the clinical signs.
Some breeds of dogs are at increased risk for developing discoid lupus. These include collies, German shepherds, and huskies.
The disease starts with loss of pigmentation; for example, a black nose may acquire a gray color. This progresses into destruction of the tissue, and in more advanced cases, ulcerations and crusts or scabs are seen in more advanced cases.
This disease is benign and the animals are otherwise healthy. The loss of pigmentation, however, predisposes affected animals to sunburn, and in rare cases may lead to the development of skin cancer (squamous cell carcinoma). The severity of the disease is variable. In some animals the disease is mild and has a waxing and waning course, while in others the disease is more aggressive, leading to destruction of part of the nose. Severe cases require treatment that is usually life long.
Diagnosis
Diagnosis is made by clinical signs and by biopsy in which a small piece of skin is removed, and stitches are placed to ensure fast healing.
Sedation is required in most cases to take skin samples from the face. Thus, your animal will receive a combination of drugs to cause sleepiness and minimize the discomfort of this procedure.
It is important that a definitive diagnosis is established, as there are more serious diseases that can look like discoid lupus. One example is a form of cutaneous lymphoma called mycosis fungoides. It starts with loss of pigmentation of the nose and lips and then progresses into ulcerations. Prognosis for this type of lymphoma is poor. Biopsy is crucial to differentiate between similar diseases.
Treatment
In some dogs, sun avoidance is sufficient to control the disease and no further treatment is necessary, while in other cases treatment is necessary.
Vitamin E may be beneficial in mild cases. Also a combination of tetracycline and niacinamide may be effective in mild to moderate cases.
Topical steroids may be used on the nose. They reduce the inflammation and promote healing of the sores. Gloves should be used when applying these products to minimize absorption.
More severe cases may require immunosuppressive drugs. If systemic steroids are used it is important that you monitor your dog for adverse effects. They include gastrointestinal ulcerations that cause vomiting, diarrhea, dark brown/black stools and loss of appetite; increased thirst; increased urination; and increased appetite.
Your dog will need frequent blood work to ensure that the cell counts do not decrease too much. This is especially important when a combination of drugs is used. This type of therapy is reserved only for severe cases.
Home Care and Prevention
Sun exposure should be avoided. Your dog should be kept inside in the middle of the day and water-proof sunscreens should be applied to the nose.
There is no prevention for this disease. However, sun avoidance can greatly reduce the severity of clinical signs.
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