Description
Discoid lupus erythematosus is an uncommon immune-mediated disease which primarily affects the skin, especially around the noseand nearly always the planum of the nose, the lips and eyes. It sometimes affects the ears in dogs, and often affects the ears in cats. Rarely  it affects the penile sheath or toes in dogs.

Breed Occurrence
This condition is reported to be more common in German Shepherd Dogs,  Rough Collies, Shetland Sheepdogs and Siberian Huskies.

It is very rare in cats.

Diagnosis

Diagnosis is confirmed on skin biopsy taken from affected areas.

Immunological tests such as immunofluorescence are not usually necessary, and antinuclear-antibody tests are usually negative. 

Treatment

Systemic (tablet or injection) or topical (creams) corticosteroids (eg prednisolone) are used to induce and maintain remission, with long-term low-dose intermittent treatment being preferred.

Strategies to reduce exposure to the sun are also helpful - eg keep the animal indoors and protected from strong sunlight. Use sun-blocking creams. 

High doses of vitamin E (400-800 IU/day) have been reported to be of benefit in some cases., as has the use of niacinamide in combination with tetracycline (250mg of each three times daily by mouth for dogs under 10kg body weight, 500mg of each at the same rate for dogs over 10kg body weight

Prognosis

Good. this is not a life-threatening disorder.