Section: Veterinary Care In-depth
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.
Treatment In-depth
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.
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