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A 6-year-old Dachshund was presented with a 2-day history of lethargy, anorexia and cutaneous erythema, edema, and multifocal erythematous papules affecting the ventral abdomen, axillae, and groin. Microscopic examination revealed a sterile neutrophilic dermatitis resembling Sweet’s syndrome; however, extracutaneous lesions were not present. The condition responded rapidly to corticosteroid therapy.
Dermatite neutrophilique stérile canine (ressemblant au syndrome de Sweet chez l’humain) chez un teckel. Un teckel de 6 ans a été présenté avec une histoire d’abattement, d’anorexie ainsi que de l’érythrodermie, de l’œdème et des papules érythémateuses sur l’aspect ventral de l’abdomen, les aisselles, et l’aine. L’examen microscopique a démontré une dermatite neutrophilique stérile s’apparentant au syndrome de Sweet chez l’humain. Cependant, ce chien ne présentait pas de manifestation extracutanée. Ce cas a répondu rapidement à une corticothérapie.
(Traduit par les auteurs)
A 6-year-old spayed female Dachshund was referred to the Faculté de médecine vétérinaire of the Université de Montréal with a 2-day history of lethargy and anorexia coinciding with the sudden appearance of severe cutaneous erythema and slight edema, affecting the ventral aspect of the abdomen, the axillae, and the groin. The edema extended ventrally to involve the legs. The dog was not receiving any medication and had been last vaccinated about 9 mo previously.
On presentation, the dog was lethargic, moderately dehydrated, and afebrile. Numerous non-pruritic papules, up to 1 cm in diameter were present on the ventral aspect of the abdomen, the axillae, and the groin. A urinalysis, complete blood (cell) count (CBC) and biochemistry profile revealed a slight increase in alkaline phosphatase (110 U/L; reference range: 6 to 80 U/L) and moderate hypoalbuminemia (21.1 g/L; reference range: 29.1 to 30.7 g/L). Prothrombin time and activated partial thromboplastin time were within reference ranges. Antinuclear antibody titers and tests for Ehrlichia canis, Anaplasma sp., Borrelia burgdorferi and leptospirosis were all negative. Thoracic radiographs and abdominal ultrasound did not reveal changes indicative of systemic disease. Three 6-mm diameter punch biopsies were taken from the skin of the affected area. Microbiological culture of the samples did not yield growth of any microorganisms.
The macroscopic appearance of the lesions, combined with the sudden onset suggested an immune-mediated process and so the dog was treated with immunosuppressive doses of corticosteroids [dexamethasone (Dexamethasone 5 mg/mL; Vétoquinol, Lavaltrie, Quebec), 0.15 mg/kg body weight (BW) SQ followed by oral prednisolone (Prednisolone 5 mg; Rafter, Calgary, Alberta), 2 mg/kg BW/d] and doxycycline [Novo-Doxylin 100 mg; Novopharm (Teva), Toronto, Ontario], 5 mg/kg BW, PO, q12h, while waiting for the biopsy results. The cutaneous lesions improved dramatically over the first 48 h and there was a complete clinical remission within the first week of treatment.
The microscopic appearance revealed similar changes varying in severity in all of the biopsies. Throughout the superficial, middle, and to a lesser extent, the deep dermis, most of the venules were lined with plump endothelial cells, and contained variable numbers of marginating neutrophils, but there was no evidence of vasculitis. The dermis contained an infiltrate of a moderate number of neutrophils that had a perivascular to a more dispersed distribution. Occasionally, especially in the superficial dermis, these non-degenerate neutrophils formed a dense infiltrate or were loosely arranged in nodules (Figure 1). The inflammatory infiltrate also contained small numbers of lymphocytes, plasma cells and macrophages with occasional eosinophils and mast cells. There were small multifocal areas of hemorrhage in the superficial dermis. Diffusely, there was congestion and marked edema of the superficial, middle, and deep dermis with moderate separation of dermal collagen bundles and marked distension of dermal lymphatic vessels (Figure 2). Diffusely, within the epidermis, there was a mild acanthosis and orthokeratotic hyperkeratosis that extended into the follicles. Multifocally, there was a mild spongiosis affecting the basal and spinous layers. Special stains (Gram, modified acid fast, Gomori’s methenamine silver) failed to demonstrate the presence of bacteria or fungi. The diagnosis was an acute multifocal perivascular to interstitial neutrophilic dermatitis with marked dermal edema.
The failure to demonstrate the presence of an infectious agent, the non-degenerate nature of the neutrophils, the dermal edema, as the predominant change, combined with the clinical signs of sudden onset of erythema, edema and multifocal papules, suggested an urticarial hypersensitivity reaction. The clinical signs, the macroscopic and microscopic appearance, and the failure to demonstrate infectious agents, are consistent with the canine sterile neutrophilic dermatosis syndrome (1).
Canine sterile neutrophilic dermatosis is a rarely reported disease in the veterinary literature (1), with only few individual case reports (2–5). Clinical descriptions report multiple macules, erythematous papules or irregular plaques, occasionally with minute pustules (1). Microscopically, there is dermal edema with a moderate to severe perivascular to diffuse neutrophilic infiltrate, occasionally with dermal hemorrhage (1). Leukocytoclasia (nuclear fragmentation) of neutrophils passing through vessel walls may also be present (1). Previous published reports of neutrophilic dermatosis in dogs also describe various extracutaneous manifestations of disease including, fever (2,5), arthritis/synovitis (2,3,5), myocarditis (2), pneumonia (2), lymphadenopathy (2), esophagitis (2), normocytic normochromic anemia (3,4), lymphopenia (3), thrombocytopenia (4), vascular necrosis (3) or vasculitis (2,4). Gross et al (1) describe extracutaneous disease as part of the syndrome, which may include fever, arthritis, pneumonia and a neutrophilic leukocytosis; however, they state that there is generally no vascular necrosis or thrombosis. Our case is similar both macroscopically and microscopically, but there was no extracutaneous disease.
An acute febrile neutrophilic dermatosis in human patients was first described as Sweet’s syndrome by Dr. R.D. Sweet in 1964 (6). However, currently, fever and neutrophilia are considered variable features and extracutaneous manifestations are described as common (7) rather than obligatory. Major and minor criteria have been proposed for a diagnosis of an acute febrile neutrophilic dermatosis. The diagnosis is based on the presence of 2 major criteria (acute onset of typical cutaneous lesions and compatible histopathological findings) and 2 minor criteria (history of a previous disease/vaccination/pregnancy associated with that syndrome; fever; leukocytosis; and rapid response to glucocorticoid therapy) (8).
The present case differs from previously described canine cases in that it lacks extracutaneous disease, but fits within the criteria that define Sweet’s syndrome. The lack of an infectious agent and the rapid response to corticosteroid therapy are other important features of the syndrome in both humans and our case. The early recognition of the dermatological signs, followed by prompt and aggressive treatment with corticosteroids may have pre-empted the appearance of extracutaneous manifestations; however, in human cases fever and neutrophilia are usually coincident with the neutrophilic dermatosis (7,9).
The cause of Sweet’s syndrome in humans and dogs is unknown. The cutaneous changes suggest that an immune-mediated hypersensitivity reaction may be part of the pathogenesis (8). The response to corticosteroid therapy supports this proposed pathogenesis. Sweet’s syndrome is associated with many diseases that involve circulating immune complexes (such as, ulcerative colitis, Crohn’s disease, systemic lupus erythematosus, rheumatoid arthritis, Sjögren’s syndrome), numerous malignancies (for example, myelogenous leukemia, breast cancer, prostate cancer), previous infections (infection with Staphylococcus or Streptococcus, tuberculosis, hepatitis, HIV), as well as various drugs, immunizations, or even pregnancy (7). Solar radiation has also been linked to the induction of some cases (7). Similar to many immune-mediated diseases, an association between some cases of Sweet’s syndrome and some human leukocyte antigens (HLA) has been described (10). It has also been suggested that the pathogenesis may be mediated by helper T-lymphocyte type I cytokines, such as IL-2 and IFN-γ (11). Circulating immune complexes have not been confirmed in Sweet’s syndrome (7) and have not been described in canine neutrophilic dermatosis (2–5). However in 1 case an adverse reaction to carprofen was suspected, part of the syndrome involved an immune-mediated hematological disorder (4).
Thus Sweet’s syndrome appears to represent an immune-mediated hypersensitivity response to a variety of antigens resulting in a sterile neutrophilic dermatosis with variable fever, neutrophilia, and extracutaneous diseases. The case of canine sterile neutrophilic dermatitis described in this report differs from previous canine cases in that it lacks extracutaneous manifestations and has no evidence of any other associated disease. However, combined with previous canine cases, our case completes the range of canine neutrophilic dermatosis that parallel those described in the human literature under the designation “Sweet’s syndrome.”
The differential diagnosis of Sweet’s syndrome includes other neutrophilic dermatoses of infectious cause, such as mycobacterial, other bacterial or fungal, and neutrophilic vasculitis (1,9). Numerous canine dermatoses characterized by papules, pustules, plaques such as erythema multiforme and pemphigus foliaceus could also be considered (1). Neutrophilic dermatoses of infectious cause are relatively common in dogs, but canine sterile neutrophilic dermatoses are rarely described. Sterile neutrophilic dermatitis should be considered as a differential diagnosis when acute dermatitis is present with or without extracutaneous manifestations of disease and when infectious agents cannot be demonstrated within the lesion. CVJ
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