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
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 of Discoid Lupus in Dogs
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.
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.
Related Diseases to Canine Discoid Lupus
Other diseases that have signs of nasal depigmentation and crusting include:
Contact dermatitis (allergic and irritant)
Nasal solar dermatitis
In areas that are necrotic and ulcerated, vasculitis should be considered. Vasculitis could also be secondary to:
Autoimmune in origin
In-depth Diagnostic Information on Discoid Lupus in Dogs
Diagnosis is based on history (waxing and waning course, lesions aggravated by UV light exposure), clinical signs and histopathology.
Histopathology. This is concerned with the changes in diseased tissue. Early depigmented lesions are the best for biopsies.
Immunohistochemistry to detect antibody deposition in tissues may reveal a positive staining at the level of the basement membrane in dogs with discoid lupus. In the literature, the percentage of positive cases varies from 25 to 100 percent. C3 is the most commonly detected immunoreactant. IgG, IgM, and IgA may also be detected. Immunohistochemistry can be done on formalin fixed samples. Thus, the same sample can be used for both routine histopathology and immunohistochemistry. It is important to note, however, that nose and footpads of normal dogs may have a positive staining, thus these areas should be avoided for immunohistochemistry.
Glucocorticoid therapy may result in falsely negative immunohistochemistry results.
Direct immunofluorescence to detect antibody deposition in tissues may also be positive in cases of discoid lupus. A special medium (Michel’s medium) should be used and care should be used to avoid changes in the pH of the medium. For these reasons, immunohistochemistry is now preferred over direct immunofluorescence.
Indirect immunofluorescence (to detect circulating antibodies) is negative in cases of discoid lupus.
Antinuclear antibody is usually negative.
Prognosis for discoid lupus is good. However, therapy may be required for life and depigmentation may predispose to sunburn.
In-depth Treatment Information on Discoid Lupus in Dogs
Mild cases may not require treatment. In those cases it may be sufficient to avoid sun exposure and to use sunscreens.
Vitamin E at 400 to 800 IU twice daily orally is rarely effective by itself, but it may be helpful in decreasing the need for other drugs.
High doses of essential fatty acids may be helpful in some cases.
A combination of niacinamide and tetracycline has been reported to be effective in 70 percent of cases with discoid lupus erythematosus.
The precise mechanism is not known, but it is hypothesized that the effect is related to the anti-inflammatory properties of tetracyclines in conjunction with the ability of niacinamide to stabilize mast cells and prevent cell degranulation.
Dogs that weigh more than 20 pounds receive 500 mg of tetracycline and niacinamide three times daily and dogs weighing less than 20 pounds receive 250 mg of each drug. It should be tried for 8 weeks before assessing the efficacy. Adverse effects include vomiting, diarrhea and anorexia.
Topical glucocorticoids may be quite beneficial. Topical fluocinolone (Synotic) may be used twice daily during the induction period (10 to 14 days). Once the disease is in remission, it should be used every other day or every third day. Less potent steroids may also be tried (hydrocortisone).
In severe cases, systemic glucocorticoids may be used. Oral prednisone is used at 1 mg per pound twice daily for induction period, and then slowly tapered to a maintenance dose. Systemic glucocorticoids may be combined with other immunosuppressive drugs.
Azathioprine can be used at 1 mg per pound every other day. It is a purine analog and affects T cell proliferation. Azathioprine has a lag phase of 6 weeks, thus clinical efficacy is not noted at the beginning of therapy. Close monitoring of these patients is recommended.
Complete blood counts and platelet counts should be repeated every 2 weeks at the beginning of therapy. In addition azathioprine can result in hepatitis and pancreatitis.
Chemistry panels every 4 months are recommended.
Chlorambucile is an alkylating agent that may be used in place of azathioprine at oral dose of 0.1 mg per pound every other day. It has potential for bone marrow suppression, but it appears to be safer than azathioprine.