What is Discoid Lupus Erythematosus?
Discoid lupus erythematosus (DLE), also known as cutaneous lupus erythematosus, is an autoimmune disease that affects the skin. There are two other types of lupus that affect the skin: vesicular cutaneous lupus erythematosus and exfoliative cutaneous lupus, both of which are relatively uncommon.
Discoid lupus erythematosus is the most common type of cutaneous (skin) lupus in dogs. This condition is very rare in cats. Dogs with DLE develop crusting and scabbing of the skin, most commonly starting around the nose, as well as a loss of skin pigmentation in the affected area.
What causes DLE?
Discoid lupus erythematosus is an auto-immune disease, in which the body’s own immune system is activated to attack the body. This immune attack kills a layer of cells within the skin, causing the surface of the skin to slough.
The underlying cause of DLE is unknown. It has been noted that ultraviolet (UV) light appears to worsen DLE and the condition is more common in sunny climates. Inflammation triggered by UV radiation is thought to contribute to this condition.
What are the signs of DLE?
Dogs with DLE typically develop erosions, ulcers, and depigmented areas (light discoloration of the skin) around the nose. In many patients, the nasal planum (the hairless area surrounding the nostrils) will become smooth, losing its bumpy, cobblestone-like texture. The skin around the nose also has a well-developed blood supply, so heavy bleeding can result if skin lesions are located near a major blood vessel.
In some dogs, the skin lesions spread to other areas of the body. These lesions most commonly affect the skin around the eyes, on the ear flaps (pinnae), and around the genitals. Skin lesions can also become generalized, spreading across the entire body, though this is uncommon.
How is DLE diagnosed?
The diagnosis of DLE requires a skin biopsy. Your veterinarian will obtain a small sample from a skin lesion using an instrument called a punch biopsy. This instrument allows the removal of a small, circular plug of skin. Your dog will likely require general anesthesia or heavy sedation for this procedure, because the skin on the face and muzzle is very sensitive.
Once the skin biopsy sample has been removed, the biopsy site will be closed with sutures. Depending on the type of suture used, your veterinarian may have you return at a later date to have sutures removed. If your veterinarian used dissolving sutures, the sutures will dissolve on their own in the coming weeks.
After removal, the skin sample will be sent to a pathologist for analysis. By processing the skin sample and examining it under a microscope, the pathologist will be able to determine whether your dog has DLE.
Dogs with DLE often have secondary bacterial infections in affected areas. Your veterinarian may recommend antibiotic therapy before performing a skin biopsy, in order to minimize the chances of an infection interfering with obtaining accurate results. Additionally, your veterinarian may recommend performing bacterial cultures at the time of the biopsy to ensure that no further antibiotic therapy is needed.
How is DLE treated?
Discoid lupus erythematosus is an autoimmune disease. Therefore, treatment requires suppression of the immune system. Dogs differ in their response to treatment, so a trial-and-error approach is often needed to determine the best medication or combination of medications for each patient.
Some dogs respond well to topical medications. These topical medications may include tacrolimus ointment or a topical steroid cream. If topical therapies are used, your dog will need to be prevented from licking the medication for ten minutes in order to allow adequate contact for the medication to be effective. Many clients find that feeding their dog a meal, giving a tasty food treat, or walking their dog may distract them, while other owners need to apply a muzzle for a brief period of time to keep the mouth closed and prevent licking.
Some dogs require systemic medications. A combination of tetracycline (an antibiotic) and niacinamide (Vitamin B3) is often used for its anti-inflammatory effect. Some dogs will require more aggressive immune suppressants, such as cyclosporine (Atopica™) or low doses of steroids.
In some cases, both topical and systemic therapies are used in combination to give the best results.
Regardless of which treatment is used, treatment should be continued until the lesions are fully resolved. It may take months for the nasal planum to regain its normal color, but the resolution of crusting and ulceration will indicate that the inflammation has resolved. Once all of the lesions have resolved, and no new lesions are noted, your veterinarian will help you gradually taper your dog’s medications to the lowest effective dose that prevents new flare-ups.
Finally, it is important to keep in mind that UV light is a known contributing factor in cases of DLE. Dogs with DLE should have their sun exposure minimized as much as possible. These dogs should be kept indoors as much as possible during daylight hours, and be walked in the early morning or late evening hours if possible. If a dog with DLE absolutely must be housed outdoors, it is important that the dog’s enclosure be fully shaded.
What is my dog’s prognosis?
The prognosis for DLE is good. Most dogs can have their signs controlled with appropriate follow-up care and ongoing therapy. Signs may wax and wane, so your dog may have repeated episodes over his lifetime that require treatment. Consistent follow-up care is likely to limit DLE’s impact on your dog’s quality of life.
If untreated, DLE can make dogs more likely to develop a type of skin cancer known as squamous cell carcinoma. Your veterinarian will want to recheck your dog’s skin lesions at each recurrence or if any change is noticed in appearance. If a new or unusual lesion develops, a skin biopsy will help your veterinarian be sure that this is only a manifestation of the DLE and not the development of a skin tumor.
