Discriminatory features of acute eosinophilic dermatitis with oedema (Wells‐like syndrome) and sterile neutrophilic dermatosis (Sweet's‐like syndrome) in dogs

BACKGROUND: Canine acute eosinophilic dermatitis with oedema (CAEDE) and sterile neutrophilic dermatosis have overlapping clinical and histopathological features. HYPOTHESIS/OBJECTIVES: The objective of this study was to identify features that differentiate these entities. ANIMALS: Forty dogs. METHODS AND MATERIALS: Retrospective case series. Forty cases with diagnoses of either CAEDE and/or sterile neutrophilic dermatosis were included based on histopathological review. Medical records (29 of 40 dogs) were reviewed for clinical findings and historical data. Commercially available immunohistochemical stains for granulocytes and a Luna stain were performed (40 of 40 dogs) to assess the granulocytic infiltrate. RESULTS: Nineteen cases had been previously diagnosed as CAEDE, seven cases had been designated as sterile neutrophilic dermatosis and 14 cases had overlapping features. Based on review and receiver operating characteristic (ROC) curve analysis, 30 cases with >12% eosinophils, enumerated by Luna staining, were diagnosed as eosinophilic dermatitis and oedema. Ten cases were diagnosed as sterile neutrophilic dermatosis. Dogs with CAEDE frequently had gastrointestinal signs (24 of 30;80%) and pruritus (11 of 30;33%). In dogs with sterile neutrophilic dermatosis, five of 10 (50%) had diagnoses of or histories compatible with immune-mediated polyarthropathy. CONCLUSIONS AND CLINICAL IMPORTANCE: In this case series, CAEDE was encountered more frequently than neutrophilic dermatosis and could be distinguished by the eosinophilic infiltrate, aided by a Luna stain. Concurrent arthralgia was more frequently identified with neutrophilic dermatosis. It remains unclear whether CAEDE and sterile neutrophilic dermatosis are separate disease entities or varied manifestations of the same disease.