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greyhounds or other breeds. A verotoxin produced by E. coli has been proposed as an inciting cause, although this has not been proven. The condition presents
initially as multifocal areas of erythematous swelling, which can evolve into ulcers. Lesions may or may not drain a serosanguineous fluid. The ventral abdomen
and extremities are most commonly affected. Affected animals are often febrile and lethargic and may or may not have gastrointestinal involvement or renal failure.
Vasculitis associated with systemic lupus erythematosus (SLE): Systemic lupus erythematosus is frequently associated with multisystemic vascular disease secondary to immune complex deposition. Although animals are frequently systemically ill by the time of appearance of cutaneous lesions, the author has recently seen a case in which cutaneous lesions preceded overt systemic illness by several months.
Other ischemic dermatopathies:
Familial canine dermatomyositis: This condition is most common in Collies and Shetland Sheepdogs but may appear in other breeds as well. The condition usually appears prior to 6 months of age, but occasionally appears in adulthood. Affected animals develop erythema, alopecia and crusting on areas prone to trauma and on pressure points. Later lesions may demonstrate erosions and ulcerations, which heal
by scarring. Lesion severity varies greatly between individuals. Affected animals may have significant clinical myopathy (often presenting as muscle weakness or atrophy of the muscles of mastication) or may demonstrate electomyographic abnormalities in the absence of clinical myositis.
Proliferative thrombovascular necrosis of the pinnae: Dachshunds and Rhodesian ridgebacks appear to be predisposed to this condition, although other breeds may also be affected. Affected pinnae demonstrate varying degrees of swelling, crusting, scaling, fissuring and bleeding. In extreme cases, overt progressive necrosis of the pinnae may be seen. Individual cases have been reported in association with drug or vaccine administration, or food hypersensitivity.
Diagnosis:
The presence of crusting, ulcerative to erosive lesions on the extremities and pinnae is strongly suggestive (but not diagnostic for) of the presence of a vasculopathy, especially when combined with punched-out lesions of the footpads. Erythematous lesions may be examined by diascopy. Failure to blanch with pressure suggests extravascular hemorrhage. It is important to note that this result may also be seen in other conditions (e.g., coagulopathies).
An Urban Experience
Skin biopsy is the definitive diagnostic tool to demonstrate the presence of a vasculitis. Samples should ideally be taken from active edges of lesions,
as these are the most likely to contain active vascular inflammation. Biopsies taken from more chronic
lesions may be suggestive of prior ischemia. Biopsies obtained of vaccine associated lesions may occasionally demonstrate deep dermal to subcutaneous inflammation associated with amorphous debris (presumed vaccine adjuvant).
Since vasculitis is considered to be a cutaneous reaction pattern rather than a specific diagnosis, any diagnostic approach must include an attempt to identify an underlying cause, although in many patients no obvious cause can be found. A thorough questioning of the owner to identify any drug administration (including vaccinations, flea and heartworm prevention) should
be performed and any suspect drugs discontinued immediately. A minimum data base (CBC, chemistry profile, urinalysis) may be useful to help detect systemic involvement and possibly demonstrate infectious diseases (e.g., Babesia, Histoplasma). Serum titers
for tick-borne diseases are indicated in endemic
areas. Tissue or blood cultures may be appropriate. If systemic involvement is demonstrated, an anti-nuclear antibody test may help to identify SLE. In severe
cases, coagulation panels may detect the presence of hypercoagulability and provide prognostic value.
Therapy:
Effective therapy involves the identification and elimination of underlying disease, whenever possible.
If the condition is thought to be vaccine-associated,
it may be prudent to avoid further vaccination in that animal, where laws permit this option. If re-vaccination is unavoidable, eliminating optional vaccines and minimizing the number of vaccines given at any one time may be advisable.
Symptomatic management of vasculopathy generally involves a combination of anti-inflammatory medications (reviewed in Innera 2013 and Morris 2013). Pentoxifylline is often useful as a sole or adjunct therapy because of its several anti-inflammatory effects. A wide range of doses have been suggested for this drug, with 20mg/ kg TID being the author’s preference. Other therapies used for less severe cases of vasculitis include Vitamin E and the combination of tetracycline (or doxycycline) and niacinamide.
More severe cases may benefit from systemic glucocorticoids at high anti-inflammatory to immunosuppressive dosages. Prolonged administration of high doses may be counterproductive, but intermittent “pulse” administration may be useful for treatment of flares. Potent topical glucocorticoids may be used as adjunctive treatment for individual refractory lesions,
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