1. General Considerations

   1. Facial discoid lupus erythematosus also referred as discoid or cutaneous lupus erythematosus, is the second most common autoimmune skin disease reported in dogs, after pemphigus foliaceus.
   2. It is rarely reported in cats.
   3. facial discoid lupus erythematosus is a relatively benign nasal planum-predominant skin disease with no systemic signs.
   4. Canine breeds commonly affected include collies, Shetland sheepdogs, German shepherd dogs, and Siberian huskies.

2. Clinical Signs

   1. Signalment: The information is based on a comprehensive review article on cutaneous lupus erythematosus in dogs.
      1. German shepherd dogs and their crosses accounted for 32/104 (31%) of the cases.
      2. Reported age of onset range from 1 to 12 years (median: 7 years).
      3. The female/male ratio is 0.7.
   2. Lesions:
      1. Lesions usually start as depigmentation, erythema, and scaling of the nasal planum and progress to deep erosions or shallow ulcers, crusts and loss of architecture of the nasal planum skin in chronic cases.

1. 1. 2. Lesions usually heal with atrophic and sometimes disfiguring scars characterized by depigmentation and loss of normal cobblestone architecture of the nose.

1. 1. 3. Lesions are exacerbated by sunlight because the skin pigment is lost.

1. 3. Lesion distribution:
      1. Lesions are most often limited to the nasal planum.

1. 1. 2. Other body regions that are less commonly affected include the dorsal-proximal muzzle, periocular skin, pinnae, and lips.

3. Diagnosis

   1. Differential diagnoses:
      1. Pemphigus foliaceus, pemphigus erythematosus, mucocutaneous pyoderma, uveodermatological syndrome, and epitheliotropic T cell lymphoma.
   2. Characteristic history and clinical signs are important parts of the diagnosis equation.
   3. Cytology:
      1. Acantholytic cells are not present. This helps differentiate facial discoid lupus erythematosus from pemphigus foliaceus and pemphigus erythematosus.
      2. Evidence of a secondary bacterial infection is common.
   4. Histopathology:
      1. Interface dermatitis reaction characterized by hydropic-vacuolar changes at the basement membrane zone and basal cell layer and lichenoid band-like infiltrate at the dermal-epidermal junction consisting primarily of lymphocytes and plasma cells. The lichenoid band-like infiltrate at the dermal-epidermal junction can be seen with other inflammatory disease of the nasal planum. Individual apoptotic keratinocytes in the lower epidermis and pigmentary incontinence are additional findings.

1. 1. 2. Select non-ulcerated depigmented macules to biopsy.
   5. Direct immunofluorescence or immunohistochemistry:
      1. Deposition of immunoglobulin or complement at the basement membrane zone resulting in fluorescence or peroxidase reaction at the dermal-epidermal junction.
      2. Remember! Do not rule out facial discoid lupus erythematosus if the results are negative.
      3. History, clinical signs, and histopathologic findings are more valuable diagnostic tools.
      4. Preserve samples in Michel’s solution for immunofluorescence and formalin for immunohistochemistry.

1. 6. Antinuclear antibody (ANA) test:
      1. Negative or very low titers. This is not a useful test for the diagnosis of facial discoid lupus erythematosus.

4. Treatment

   1. Prognosis is usually good with appropriate therapy.
   2. Treatment has to be individualized due to the wide spectrum of clinical presentation among the animals.
   3. One or more of the following are treatment options for facial discoid lupus erythematosus: (See below “Therapy for Autoimmune Diseases” for dose or specifics on treatment regimens).
      1. Glucocorticoids – Oral and/or topical.
      2. Cyclosporine or topical tacrolimus (Protopic® ointment 0.1% or 0.03%).
      3. Oclacitinib (Apoquel®) – Anecdotal reports have shown its good efficacy in treating facial discoid lupus erythematosus.
      4. A tetracycline (i.e. tetracycline, doxycycline, minocycline) and niacinamide. Try to avoid this treatment modality to prevent bacterial resistance to antibiotics (practice antibiotic stewardship).
      5. Azathioprine – May be used in dogs for the treatment of refractory cases.
      6. Sunscreen – Important to protect against sun damage.

References

Medleau L, Hnilica KA. Chapter 8. Autoimmune and immune-mediated skin disorders. In: Small Animal Dermatology: A color Atlas and Therapeutic Guide 2006. 2nd ed. W.B. Saunders, Missouri, 189-227.

Miller, Griffin and Campbell.  Chapter 9. Autoimmune and immune-mediated dermatoses. In: Muller & Kirk’s Small Animal Dermatology 2013. 7th ed., W.B. Saunders, Missouri; 432-462.

Olivry T. Auto-immune skin disease in animals: time to reclassify and review after 40 years. BMC Vet Res 2018; https://doi.org/10.1186/s12917-018-1477-1.

Olivry T, Chan LS. Autoimmune blistering dermatoses in domestic animals. Clin Dermatol 2001; 19(6):750-760.

Olivry T, Linder KE, Banovic F. Cutaneous lupus erythematosus in dogs: a comprehensive review. BMC Vet Res 2018; https://doi.org/10.1186/s12917-018-1446-8.