Cutaneous vasculitis

Dr. Irina Matricoti, DVM, Diplomate ECVD

The term vasculitis refers to a pathological reaction pattern, characterised by inflammation affecting the vessel wall; vasculitis is therefore not a definitive clinical diagnosis.

Vasculitis is often immunological in nature, generally associated with underlying diseases, which should always be investigated. These can be infections (bacterial, viral, fungal, protozoal), drug reactions (e.g. to penicillins, sulphonamides, febendazole, ivermectin, itraconazole etc.) or reactions to vaccines, or other immunological diseases, such as allergic reactions or autoimmune diseases (e.g. lupus). Inflammation of the vessels can also be triggered by non-immunological mechanisms, such as neoplastic diseases or following burns. However, as it is not always possible to identify the underlying cause, so that some of these reactions are considered idiopathic in nature (1).

The immunological mechanism underlying the majority of cutaneous vasculitis cases is a type III hypersensitivity reaction, characterised by the deposition of immune complexes in the vessel wall and the subsequent inflammatory reaction against them. In addition to the immunological mechanism, other alterations, such as changes in blood flow and permeability of the vessel wall, can also participate in this inflammation. Since certain vasculitides recur in certain breeds, a genetic component contributing to the pathogenesis of these dermatopathies is also conceivable (1,2).

Dermatological lesions of vasculitis occur most frequently in areas of pressure or friction and on the extremities, e.g. limbs, pads, apex of ears, nose, tail and fingertips. In acute phases, haemorrhagic purpura, petechiae, scales, crusts, crater-like ulcerative lesions or onychomadesis may appear.

In chronic ischaemic forms, where dermatological lesions are mostly related to insufficient blood supply, patients frequently present with non-inflammatory, sometimes scarring multifocal alopecia (1-3), as well as scales, crusts and ulcers.

Ischaemic dermatopathies include dermatomyositis, post-vaccine generalised ischaemic dermatopathies, focal panniculitis due to rabies vaccination and idiopathic ischaemic dermatopathies. Small breeds are most affected, particularly Chihuahuas, Maltese and poodles (3).

In the field of vasculitis, certain forms typical of certain breeds are described. In the cutaneous and renal vasculopathy of the Greyhound the skin lesions are predominantly ulcerative and are localised on the limbs, trunk and groin. Oedema of the limbs may also be present. In addition to cutaneous signs, patients present with acute renal failure with onset of hyperazotemia and hypercreatininemia, hypoalbuminemia, anaemia and systemic clinical signs such as hyperthermia, depression, gastrointestinal or neurological symptoms. Dermatological lesions generally precede the onset of the renal failure. In addition to Greyhounds, this syndrome has also been described in other dog breeds, with frequent onset between November and May. To date, the cause has not yet been identified (4).

Nasal filter arteritis is particularly reported in the giant Schnauzer and the St. Bernard, in which it is presumed to be hereditary. The lesion is localised in the centre of the nasal filter and appears as a linear ulcer, sometimes associated with depigmentation (5). The familial vasculopathy of the German shepherd can be seen in puppies around two months of age, the period coinciding with the first vaccinations. The animals show focal depigmentations, followed by ulcers on the foot pads, and often also hyperthermia, lethargy, lymphadenomegaly and arthropathy. A familial cutaneous vasculitis has been described also in the Jack Russell terrier, with early onset, usually under one year of age. In this breed, ulcerative or ischaemic atrophic lesions mainly involve the ears and head.

A hereditary form called nasal plane vasculitis in the Scottish terrier was reported with progressive ulceration of the nasal plane until its complete destruction, already from the first months of life (6). Finally, a thrombovascular proliferative necrosis of the pinna, with ulcerative lesions at the apex of the auricle, may have a predisposition for the Rhodesian Ridgeback and the Chihuahua.

For a correct diagnostic procedure, a clinical examination is necessary to identify dermatological lesions suggestive of a vascular pathology (flaky ulcers, scabs, non-inflammatory alopecia) and their location (points of pressure or friction, bony prominence, ear or tail tips, point of vaccine inoculation). Subsequently, multiple skin biopsies are taken for histopathological examination. Once the presence of vasculitis is confirmed, it is necessary to investigate possible underlying diseases and assess the impairment of other organs, by means of haematobiochemical tests, capillary protein electrophoresis and serological tests for vector-borne diseases. If examinations for vector-borne infectious diseases are negative and no medication or vaccines were administered prior to the onset of the clinical signs (an interval of up to four months should be considered for vaccinations), then the dermatopathy is considered to be idiopathic in origin. In familial forms with juvenile onset, a genetic cause is presumed.?

Therapy of vascular dermatopathies involves the use of immunomodulatory drugs such as topical or systemic glucocorticoids, tetracyclines in combination with niacinamide, pentoxifylline or calcineurin inhibitors (cyclosporine). The protocols are the same as those used in autoimmune diseases. Recently oclacitinib has also been suggested for the treatment of vasculitis: it has been reported to be effective in dogs suffering from ear-tip ulcerative dermatitis of idiopathic origin, at the dose commonly used for the management of allergic dermatitis (0.4-0.6 mg kg every 12h for 14 days then every 24h), even in dogs unresponsive to glucocorticoids (7,8).

Bibliographic references

1.Nichols PR, Morris DO., Beale K M.. A retrospective study of canine and feline cutaneous vasculitis. Veterinary Dermatology, 2001, 12: 255-264.

2. Scott DW, Miller WH, Griffin CE. Muller and Kirk's Small Animal Dermatology, 6th Edition. Philadelphia: WB Saunders Company, 2001.

3. Backel KA, Bradley CW, Cain CL et al. Canine ischaemic dermatopathy: a retrospective study of 177 cases (2005-2016). Veterinary Dermatology 2019 30: 403-e122.

4.Walker J J J. A, Holm L P, Sarmiento óG et al. Clinicopathological features of cutaneous and renal glomerular vasculopathy in 178 dogs. Veterinary Record, 2021, 189(4):e-72.

5. Souza CP, Torres SM, Koch SN et al. Dermal arteritis of the nasal philtrum: a retrospective study of 23 dogs. Veterinary Dermatology, 2019 30:511-e155.

6. Sartori R, Colombo V, Colombo S et al. Nasal Planum Vasculopathy in a Scottish Terrier Dog Treated with Cyclosporin and Endonasal Stents. Veterinary Sciences 2018, 5:, 73

7. Colombo S, Cornegliani L, Vercelli A et al. Ear tip ulcerative dermatitis treated with oclacitinib in 25 dogs: a retrospective case series. Veterinary Dermatology 2021, 32, 363-e100.

8. Levy BJ, Linder KE, Olivry, T. The role of oclacitinib in the management of ischaemic dermatopathy in four dogs. Veterinary Dermatology 2019, 30: 201-e63.