Vasculitis happens when an overzealous immune system attacks blood vessel walls, interfering with their ability to carry blood to the tissues of the body. The condition causes inflammation and necrosis, and tends to happen where other collateral circulation is deficient, like the ears, lips, and tail tip, so one big mess can result.
We don’t know for sure what mechanism causes vasculitis, but it does in part appear to be a hypersensitivity reaction that triggers immune complexes. About half of the time, we can’t find an exact underlying cause, and we call those cases “idiopathic.” For the other 50% of cases, an underlying cause can be found. Coexisting disease or predisposing factors include:
Bacterial blood infections
Insect bite hypersensitivity
Systemic lupus erythematosus
Rocky Mountain Spotted Fever
Some breeds may be predisposed. Vaccine hypersensitivity induced vasculitis is more common in small breeds like Poodles, Yorkshire Terries, Maltese, and Silky Terriers.
Non-vaccine related vasculitis is more common in Jack Russell terriers, Scottish terriers, German Shepherds, Greyhounds, Dachshunds, and Rottweilers, suggesting that there is a genetic component to the disease.
Clinical signs of vasculitis are usually quite apparent. Blisters, ulcers, pustules, and crusty lesions can be seen on the skin, often in the places mentioned above, like the ears and lips. Bruising and swelling can also be seen.
Diagnosis may be suspected upon examining the lesions, but definitive diagnosis requires a biopsy to confirm.
Treatment of vasculitis is two step; first, the underlying cause must be managed and second, the overactive immune response must be suppressed. The prognosis is good for cases in which the underlying cause can be found and treated, but for idiopathic cases where a cause cannot be found, the response to treatment is the best indicator for prognosis.
Luckily, vasculitis is relatively rare, accounting for less than 1% of new cases that are referred to veterinary dermatologists, so chances are that you and your pet will never have to worry about it. But aren’t you glad you’re well informed (and have pet insurance) just in case you do?