Overview

• Considered to be a benign variant of systemic lupus erythematosus.
• One of the most common immune-mediated skin diseases in dogs.
• Predominantly involves the nasal planum, face, and ears with rare lesions beyond the head.

Signalment

• Dogs and cats.
• Very uncommon in cats.
• Predominant breeds-collie, German shepherd dog, Siberian husky, Shetland sheepdog, Alaskan malamute, chow chow, and their crosses.
• No age predilection.

Signs

• Initial symptom: depigmentation of nasal planum and/or lips.
• Depigmentation progresses to erosions and ulcerations.
• Loss of normal “cobblestone” architecture of the nasal planum.
• Tissue loss and scarring can occur.
• Chronic lesions are fragile and may easily hemorrhage; rarely severe hemorrhage from arteriole damage.
• May also involve pinnae and periocular region; rarely feet and genitalia.

Causes & Risk Factors

• Exact mechanism undetermined; actinic radiation may alter antigenic nature of keratinocytes.
• Seasonal and geographic exacerbation-associated with increased actinic radiation.

Differential Diagnosis

CBC/Biochemistry/Urinalysis

Normal unless due to an underlying cause

Other Laboratory Tests

ANA, LE preparation, and Coombs' tests-usually normal or negative except in SLE.

Other Diagnostic Procedures

• Biopsy and histopathology will differentiate DLE from other disorders.
• Biopsies of early lesions: depigmented areas, mild erosions, or mildly crusted lesions are preferable for diagnosis.

Pathologic Findings

• Histopathology is characterized by interface-lichenoid dermatitis with prominent basal cell apoptosis, varying degrees of epidermal atrophy, and pigment incontinence.
• Not easily differentiated from mucocutaneous pyoderma by histopathology (treatment with antibiotics prior to sampling is helpful).
• Avoid sampling severely crusted, ulcerative lesions if possible.
• Immunopathologic examination may be done but is usually not necessary.

Drug(s)

• Topical therapy:
  • Glucocorticosteroids-initially, a potent fluorinated product (e.g., 0.1% fluocinolone) q24h for 14 days; then q48–72h; once in remission switch to less-potent product (e.g., 0.5% or 2.5% hydrocortisone) if possible.
  • Tacrolimus ointment (0.1%) q12–24h initially then taper to q24–72h once in remission.
• Systemic therapy:
  • Tetracycline and niacinamide-250 mg each PO q8h for dogs <10 kg; 500 mg PO q8h for larger dogs (alternatives include doxycycline 10 mg/kg PO q24h and minocycline 5 mg/kg PO q12h).
  • Prednisone-consider for severe or non-responsive cases; 2–4 mg/kg/day either solely or in combination with azathioprine 2 mg/kg PO q48h; taper prednisone to 0.5–1 mg/kg PO q48h for long-term maintenance.
  • Cyclosporine-5–10 mg/kg PO q24h as alternative immunosuppressive therapy.
• Consider systemic antibiotic treatment for a minimum of 3–4 weeks prior to systemic immunosuppressive therapy to differentiate from mucocutaneous pyoderma.
• Vitamin E 10–20 IU/kg PO q12h; may help reduce inflammation and protect the skin.
• Hydroxychloroquine-5 mg/kg q24h; antimalarial drug that has been used in human cases.

Patient Monitoring

• Recheck 2–4 weeks after initiating treatment to evaluate for clinical response.
• CBC and biochemistry-every 12 months if using topical therapy and every 3–6 months if using systemic therapy.
• CBC and platelet counts-every 2 weeks for the first month; then every 3–6 months while on azathioprine.

Prevention/Avoidance

Affected animals should avoid ultraviolet light exposure.

Possible Complications

• Scarring
• Secondary pyoderma
• Hemorrhage
• Disfigurement

Expected Course and Prognosis

• Progressive but not usually life-threatening if left untreated.
• With proper treatment, expect remission in majority of cases.
• Cases requiring chronic immunosuppressive therapy have a more guarded prognosis, but remissions are common with more aggressive therapy.

Synonyms

• Collie nose
• Nasal solar dermatitis.

Abbreviations

• ANA = antinuclear antibody
• DLE = discoid lupus erythematosus
• LE = lupus erythematosus
• PE = pemphigus erythematosus
• PF = pemphigus foliaceus
• SLE = systemic lupus erythematosus