Cutaneous vasculitis is a term which describes inflammation of the blood vessel wall in the dermis and the subcutis, and, as such, is not a diagnosis but a cutaneous reaction pattern that can result from multiple aetiologies. Damage to the blood vessel wall and impaired blood flow result in oxygen and nutrient deprivation in the surrounding tissue, leading to hypoxia and necrosis. It has different classifications depending on the size of the vessels, type of inflammatory cells involved (neutrophils, eosinophils, lymphocytes) and on the aetiology.
Vasculitis can be immunological, eosinophilic, non-immunological or idiopathic.
Immunological vasculitis involves the deposition of immune complexes from type III hypersensitivity responses in the blood vessel walls. This in turn activates the complement cascade and recruitment of inflammatory cells to the area. Drugs, vaccines, infectious agents, food additives and neoplasia can trigger the type III hypersensitivity response.
Eosinophilic vasculitis is associated with type I hypersensitivity response and is seen in arthropod bite lesions.
Non-immunological vasculitis occurs when the endothelial cells are damaged by burns, trauma or physical blockage of blood vessels affecting the haemodynamics of blood flow.
In dogs, several breed predisposed entities of idiopathic vasculitis are recognised, where the patho-mechanism is not fully understood.
- Idiopathic vasculitis of Jack Russell Terriers
- Post-vaccine ischaemic dermatopathy in Poodles, Yorkshire Terriers, Pekingese and Maltese Terriers
- Familial vasculopathy of German Shepherd Dogs
- Idiopathic cutaneous and renal glomerular vasculopathy of Greyhounds
- Dermatomyositis in Shetland Sheepdogs, Collies and their crosses
- Dermal arteritis of the nasal philtrum
The signs vary depending on the chronicity of the lesions. Early signs such as petechiae, ecchymosis, purpura and oedema are seen. Many cases seen in practice are those that show scaling, alopecia, crusting, hyperpigmentation, erosions, ulcerations and scarring. The lesions are usually painful and usually seen on pads (Figure 1), nose, tip of tail (Figure 2), pinnae (Figure 3) and mucosal areas, where small blood vessels are most likely to be affected. Systemic signs such as fever, lethargy, anorexia, joint pain and lymphadenopathy are also seen, depending on the organ affected.
History and clinical signs are important in reaching a diagnosis. A complete drug and vaccination history is required to arrive at a conclusive diagnosis. Lesions associated with drug reactions tend to develop only after some weeks (up to six months) following the administration of the drug or vaccination. In cases where infectious disease is suspected, appropriate tests should be performed to identify the cause.
The diagnosis of vasculitis relies on demonstration of inflammatory cells targeting the blood vessel wall. In many biopsies this is not evident, because of inadequate sample size, inappropriate site selection, timing of the biopsies and secondary infections. Sometimes several sections of the biopsy are required to make the diagnosis.
Where there is an underlying disease, the differential diagnosis depends on the extent of the varying clinical signs and the extent of the disease. Autoimmune diseases such as pemphigus vulgaris, erythema multiforme, toxic epidermal necrolysis, cutaneous epitheliotropic lymphoma and sterile panniculitis are among the many differentials.
Prognosis and clinical management
The prognosis varies, depending on the cause and any underlying condition, ranging from fair to guarded. Dogs which have a single episode may recover in a few weeks, whereas in others, especially in those with a genetic disposition, the lesions tend to wax and wane.
There is no single universal drug for each condition, but there are a range of drugs with immunomodulating properties that can be employed.
For vasculitis, glucocorticoids, ciclosporin, pentoxifylline and azathioprine are used either individually or in combination depending on the individual case (Table 1). For localised lesions, topical treatments such as 0.1% tacrolimus, or betamethasone, can be beneficial. Vitamin E has antioxidant properties and is used as an adjunctive therapy. Surgery can be considered for some cases of vasculitis (ie necrotic ear tips and nasal arteritis of the nasal philtrum).
The treatment should be individualised depending on the extent of the lesions, the adverse effects of the drugs and financial constraints. For example, if the owner has limited funds one should refrain from offering azathioprine, because of the cost of the haematology and biochemical parameters that should be monitored every two weeks in the initial stages and, once stable, every two to three months. For localised lesions, topical treatment can be used to successfully manage some of the diseases.
For diseases with widespread ulceration and systemic involvement, hospitalisation and supportive treatment and wound management are necessary.
- Vasculitis is a cutaneous reaction pattern, resulting from inflammation of the blood vessel wall in the dermis and the subcutis
- The causes can be immunological, eosinophilic, non-immunological or idiopathic in nature
- The definitive diagnosis of vasculitis relies mainly on history and clinical signs supported by histopathology
- There is no single universal drug for each condition, but there are a range of drugs with immunomodulating properties that can be employed (Table 1)
- The prognosis ranges from fair to guarded, depending on the cause and any underlying condition