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Deadly dermatoses (Proceedings)

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Apr 01, 2010

Deadly dermatoses are defined as

1. Lethal diseases for the pet.
2. Diseases of the pet that lead to extreme owner frustration, leading to euthanasia of the pet.
3. Extreme owner expense, leading to euthanasia of the pet.
4. A decreased quality of the pet's life.
5. Treatment side effects that ultimately lead to euthanasia of the pet.

Auto-immune skin diseases

Any auto-immune skin disease can ultimately become a deadly dermatosis based on the criteria listed above. Examples include pemphigus foliaceus, pemphigus vulgaris and systemic lupus erythematosus.

Pemphigus Foliaceus is the most common of our auto immune skin diseases. The term pemphigus comes from the Greek word for blister, and all pemphigus diseases are blistering diseases. The hallmark of pemphigus diseases is acantholysis. Acantholysis is the process where keratinocytes lose their later cellular attachments, leading to intraepidermal clefting. Initially, it was thought that neutrophils and their mediators caused the clefts but we now realize that neutrophils invade the vesicle, leading to pustule formation. Many breeds of dogs are predisposed to pemphigus foliaceus including Akitas, Dobermans, Chow-Chows, Shar-peis and Dachshunds. Pemphigus foliaceus is typically found in middle aged dogs with a mean age of 4.2 years. Clinical signs of pemphigus foliaceus include facial crusts, ulcers and often depigmentation of the planum nasale. There are usually large, intact pustules on the trunk and face. Footpad hyperkeratosis and ulcerations are often noted, as are fevers and anorexia. Laboratory signs include a leukocytosis with neutrophilia and hyperglobulinemia are often seen with cases of pemphigus foliaceus. In addition, pets may have anemia of chronic disease or nonregenerative anemia. Cytologies of intact pustules may reveal hypersegmented neutrophils and acantholytic to lytic cells.
     • Dermatopathology shows intraepidermal pustular formation with acantholysis and neutrophils and/or eosinophils.
     • Treatments for pemphigus foliaceus include corticosteroid therapy such as Prednisone 2-4mg/kg, Imuran (azathioprine) 1-2/mg/kg EOD, Leukeran 0.1-0.2mg/kg EOD, Cyclosporine 5-10mg/kg.

Pemphigus Vulgaris is a more rare form of pemphigus and shows deeper clefting. Pemphigus vulgaris patients almost always (greater than 90%) have oral ulcerations. The erosions that are seen are more severe than with pemphigus foliaceus, and this is a much more difficult pemphigus to treat, often requiring much higher doses of steroid therapy initially to suppress the immune response.
     • Clinical signs include mucocutaneous erosions to ulcerations, severe crusting of the footpads and these ulcerations often lead to lameness.
     • Dermatopathology of pemphigus vulgaris shows intradermal pustule formation with acantholysis and neutrophils with a super basilar clefting leading to the classic row of tombstones appearance.

Cutaneous and systemic lupus erythematosus is another group of auto-immune skin diseases in our group of deadly dermatosis. Systemic lupus erythematosus is a multi-systemic disease often with mucocutaneous lesions, polyarthritis, immune-mediated thrombocytopenia, auto-immune hemolytic anemia and protein losing nephropathy. This disease is also known as the great imitator, due to the multitude of clinical signs that may be present. Systemic lupus erythematosus is a result of a type III hypersensitivity reaction. Antibodies to nucleic acid are a diagnostic hallmark for SLE (ANA positive). In one study of 75 cases of systemic lupus, the most common clinical signs are polyarthritis in 91% of the cases, renal disease in 65% of the cases and mucocutaneous skin disorders in 60% of the cases. Auto-immune hemolytic anemia was rare.
     • Diagnoses is made through a multitude of testing include ANA titers, urinalysis and urine protein/creatinine ratio, COOMBS positive test, joint fluid analysis, cytologies and skin biopsies. Skin biopsies show an interface dermatitis with a vacuolated dermal/epidermal junction and a thickened membrane zone.
     • Treatments are similar to the pemphigus cases, with corticosteroids such as Prednisone, Imuran, Leukeran and Cyclosporine.