Discoid Lupus Eryathematosus in Dogs

Tracy Libby

Discoid lupus erythematosus (DLE) is the second most frequent, though still relatively uncommon, autoimmune diseases in dogs. While it is considered by many experts to be a benign form of systemic lupus erythematosus, DLE is a disease of the skin, with lesions usually being confined to the face, although exceptions to this rule do exist. Fortunately, DLE does not progress to a systemic condition in dogs, as it does in humans. You might also know it by its nickname "Collie nose."

When Your Dog's Immune System Short Circuits

DLE is thought to arise when a dog's immune system mistakenly targets the skin. In the simplest of terms, your dog's immune system is like a border patrol, guarding his body against invaders. When the body recognizes something as foreign, or "nonself," such as bacteria, viruses or parasites, the immune system reacts by producing antibodies or sensitized lymphocytes (a type of white blood cell) that will find and destroy the intruders. In normal circumstances, the body recognizes its own tissues and organs as "self" and leaves them alone. In some instances, however, the immune system short circuits and begins misidentifying the body's "self" markers as "nonself." When this happens, an immunological attack is mounted against the dog's own tissues (or organs in the case of systemic lupus).

Several theories exist as to why a dog's immune system short-circuits and starts attacking itself, but the evidence is empirical rather than scientific. Interestingly, while a lot remains unknown about this disease, experts say some breeds, including German Shepherd Dogs, Collies, Siberian Huskies, Malamutes, Brittany Spaniels, Chow Chows, and Shetland Sheepdogs, appear more prone to developing it, which suggests genetic factors play a role. Despite the breed tendencies, it is worth noting that autoimmune diseases tend to run in families. For example, the bloodlines of a German Shepherd Dog bred in Toronto will, generally speaking, be significantly different from those of a German Shepherd Dog bred in Los Angeles.

Symptoms and Identification

Experts note an estimated 90 percent of dogs experience clinical symptoms. Symptoms most commonly involve depigmentation, erythema (abnormal redness of the skin due to inflammation) and scaling, crusting, and, oftentimes, scarring of the nasal region, and, less commonly, the lips and ear leather. In some cases, the scaling and crusting extend from the leathery portion of the nose upward to the haired muzzle and around the eyes. These lesions may ulcerate, with sun exposure frequently exacerbating the disease, which is why DLE is often worse in the summer. A hallmark of DLE is a loss of the normally "rough cobblestone-like architecture" of the nose, which changes into a smooth surface, with depigmentation, resulting in a slate gray appearance to the nose region. Bacterial infection can complicate some of the skin lesions.

Diagnosis is based on a physical examination and skin biopsies, which means small pieces of tissue must be harvested and sent to the laboratory for analysis. General anesthesia or sedation is usually required for the biopsies because of their location.

Treatment

Unfortunately, once DLE has developed, it tends to be a life-long condition and may wax and wane throughout its course. Treatment is multifaceted. In the early stages, sun avoidance and topical sunscreens, as well as topical glucocorticoids (steroids that reduce inflammation) are recommended. Vitamin E, omega-3, and omega-6 fatty acid supplementation also may be helpful. For progressive cases, the more common approach also includes the antibiotic tetracycline and the B vitamin niacinamide, as well as oral glucocorticoids, such as prednisone, which may be prescribed in addition to other immunosuppressive drugs. The goal is finding a delicate balance—suppress the immune system without opening the door to infection. Research into a treatment using the topical ointment tacrolimus (a fungus found in the soil of Mount Tsukuba, Japan) has shown good results.

If your dog has a crusty or ulcerated nose—or even small red lesions resembling a sunburn—be sure to have your veterinarian look at it right away. Early diagnosis will allow for early intervention and treatment. If the diagnosis is positive for DLE, be sure to discuss all the options with your veterinarian. 

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