Overview of Canine Discoid Lupus
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 in dogs 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 of Discoid Lupus in Dogs
Treatment of Discoid Lupus in Dogs
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.
In-depth Information on Discoid Lupus in Dogs
Discoid lupus erythematosus is an uncommon autoimmune skin disease of dogs. It is considered a benign form of systemic lupus in which the disease is limited to the skin with no systemic signs.
Discoid lupus is aggravated by exposure to UV light and is more common in areas at high altitude with direct sun exposure. The antigens against which the antibodies are directed in discoid lupus are not localized in the skin, but in the immune-complex deposits in the skin leading to cutaneous lesions (type III hypersensitivity).
In addition, it is hypothesized that sunlight may induce the expression of nuclear and cytoplasmic antigens. Specific antibodies are then produced. These antibodies will then bind to the antigen on the surface of the basal cell and this will trigger a cytotoxic process (type II hypersensitivity). The injured keratinocyte will release pro-inflammatory cytokines (interleukin 1, interleukin 6, and tumor necrosis factor alpha) that could be responsible for the accumulation of an inflammatory infiltrate in the area.
Genetics, sunlight and viruses may all be factors involved in the pathogenesis of this disease. Affected animals are otherwise healthy and have no evidence of systemic disease. Discoid lupus does not progress into systemic lupus.
Females are at increased risk for discoid lupus. The disease is confined to the face, and the nose is the most commonly affected area. Collies, German shepherds, Siberian huskies, Shetland sheepdogs and their crosses are predisposed.
Early signs include slate-blue depigmented and erythematosus macules on the planum nasale or on the lips. Loss of the normal cobblestone appearance of the nasal planum is also an early sign of disease. Depigmented lesions rapidly progress to ulcerations and crusting. Scarring may be severe in advanced cases.
Eyelids, lips, pinnae and pads are less commonly affected. Macules evolve into hairless, crusted necrotic lesions. Squamous cell carcinoma has been reported to develop in chronic cases of discoid lupus. This, however, is believed to be quite rare. Disease may run a waxing and waning course and is aggravated by sun exposure. Thus, it may have a seasonal course in some geographical areas.