Dermatology for Animals

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Discoid lupus erythematosus (DLE)

8/21/19

Also Known As: Cutaneous lupus erythematosus

Transmission or Cause: Discoid lupus erythematosus (DLE) is an autoimmune disease in which the animal’s own antibodies attack normal components of the skin. DLE is a benign variant of systemic lupus and has no systemic involvement. There is strong evidence that sunlight induces and/or exacerbates the disease process.

Affected Animals: DLE affects dogs and cats, but where it is the second most common autoimmune disease in dogs, it is very rare in cats. There appears to be neither a sex nor age predilection in either species. Collies, German shepherds, Shetland sheepdogs, Siberian huskies, Brittany spaniels, and German shorthaired pointers have demonstrated predilection for DLE.

Clinical Signs: Clinical signs of canine DLE include loss of pigmentation where the brown/black color of the nose changes to a slate blue or pink color, redness, and scaling of the nose. The disease can ultimately progress to significant destruction of the tissue, resulting in ulceration and crusting of the nose. Lesions may rarely involve the ear flaps, mouth and area surrounding the eyes. The affected dogs are otherwise healthy. In cats, DLE most commonly affects the ear and face, resulting in redness, scaling, crusting, and hair loss. Aside from the dermatologic lesions, affected dogs and cats are otherwise healthy.

Diagnosis: As this disease can resemble other more serious diseases, including epitheliotropic lymphoma (cutaneous lymphoma), pemphigus, and systemic lupus, it is important to get a definitive diagnosis. Diagnosis is based on a supporting clinical history and biopsy with histopathology. Biopsy of the nose requires sedation or general anesthesia. The nose will be numbed prior to biopsy, and sutures (stitches) will be present where the biopsy was taken.

Treatment: Treatment is variable and often dependent on severity of lesions. In some dogs, sun avoidance alone may be sufficient in controlling the disease. In more affected animals, therapy may include any individual or combination of the following: topical and/or oral steroids, oral doxycycline, an antibiotic with anti-inflammatory and immunomodulatory properties combined with niacinamide, a vitamin B derivative, and tacrolimus, an immunosuppressive topical ointment. Sun avoidance is essential in all affected animals, with applications of sunscreen providing additional protection.

Prognosis: The prognosis of DLE is generally good, as this does not cause systemic illness.

What is a histiocytoma?

7/22/19

Also Known As: Button tumor

Transmission or Cause: A benign, usually self-limiting tumor of mononuclear white blood cells in the skin which are derived from epidermal Langerhans cells.

Affected Animals: Most common in younger (< 4yr) dogs.

Clinical signs: Usually a single, rapidly growing raised, round, hairless pink, red or ulcerated skin nodule. They occur most commonly on the head, ears and legs.

Diagnosis: Needle aspirate and/or biopsy of the nodule reveals round cells which are typical histiocytes +/- associated inflammatory cells.

Treatment: In most cases, these tumors will spontaneously regress within 2-3 months due to immune stimulation. Treatment with topical or systemic steroids is therefore unnecessary and may inhibit immune clearance of the tumors. Lesions which persist for longer than 2-3 months should be removed and biopsied, and excision is curative in these cases.

Prognosis: Good, as these tumors are benign.

What is a sebaceous adenoma?

6/18/19

Also known as: Nodular sebaceous hyperplasia

Transmission or cause: A benign tumor of the oil gland (sebaceous) cells of the skin. Although these tumors are commonly called “old dog warts” due to their appearance, they are not true warts as they are not viral-induced.

Affected animals: Most common in middle aged to older dogs, especially terriers, poodles, cocker spaniels and miniature schnauzers.

Clinical signs: Single to multiple raised, hairless, lobulated white to pale pink skin or sometimes pigmented skin masses which may ooze an oily white material. Masses range in size from ¼” – 1” in diameter. Tumors occur most commonly on the trunk, legs, feet or face. They usually cause no bothersome symptoms unless they become traumatized or secondarily infected, in which case the dog may lick or chew at the lesions.

Diagnosis: Most commonly diagnosed by clinical presentation, but definitive diagnosis requires a biopsy, which reveals a benign accumulation of neoplastic sebaceous cells.

Treatment: In most cases aggressive treatment is not needed, as these are cosmetic lesions. However lesions which grow, change or bother the dog should be removed and biopsied. Surgical removal is curative but new nodules often continue to form elsewhere as the dog ages. In dogs with numerous tumors, oral retinoids (ie. isotretinion) may slow growth of nodules and decrease formation of new tumors.

Prognosis: Good, as these tumors are benign, however new tumors tend to occur as the dog ages.

What is Vasculitis?

5/17/19

Transmission or Cause: Vasculitis is inflammation of blood vessels resulting in compromise of blood supply to affected areas. The inflammation is due to overstimulation of the immune system by many possible causes including infections (bacterial, viral, fungal, or tick-borne diseases), drug or vaccine reactions, tumors, and autoimmune diseases (especially systemic lupus). In many cases, an underlying cause cannot be determined.

Affected Animals: Vasculitis is uncommon in dogs and rare in cats. Any age, breed, or gender can be affected, although some breeds may be over-represented such as Jack Russell Terriers and (in cases of vaccine-induced lesions) small silky coated breeds such as poodles and yorkies.

Clinical Signs: Symptoms include bruising, localized areas of necrotic (dead) skin and skin ulcers especially in areas such as the ear pinnae, lips, mouth, paws, tail, and scrotum. In vasculitis caused by rabies vaccination, there is localized hair loss at the site of the vaccine which can occur 1-3 months after the vaccine. Some animals with vaccine reaction can later go on to develop more generalized lesions of vasculitis. Some animals with vasculitis can show other symptoms such as lethargy, decreased appetite, fever, muscle disease, joint inflammation, and swelling of extremities.

Diagnosis: Diagnosis of vasculitis is made by clinical signs, diagnostics to identify underlying causes of the blood vessel inflammation (such as bloodwork and testing for infectious or autoimmune diseases), and skin biopsies. Skin biopsies may show inflammation of blood vessels with resultant damage to skin glands and hair follicles. Biopsies taken later in the course of disease may show more non-specific changes such as thinning or ulceration of the skin and loss of skin glands and hair follicles.

Prognosis: The prognosis depends on underlying cause, severity of symptoms, and extent of internal organ involvement.

Treatment: Treatment of vasculitis involves identifying and treating underlying causes, if possible, and using medications to suppress blood vessel inflammation. Medications which may be effective include steroids, pentoxifylline, the combination of tetracycline and niacinamide, dapsone, sulfasalazine, cyclosporin, or azathioprine. In some cases medication may eventually be discontinued, however some animals will require lifelong medication for control.

Prevention: Because there are many potential underlying causes of vasculitis, prevention is not usually possible. However, in dogs with rabies vaccine-induced vasculitis, further vaccinations should be avoided if possible, as they may exacerbate disease.

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