Sweet-like reaction due to arthropod bites: a histopathologic pitfall.

The histopathology of arthropod bite reactions is classically described as "dermal edema" with superficial and middle to deep dermal inflammation in a perivascular and wedge-shaped distribution. The composition of the infiltrate may vary, but a characteristic feature is the presence of prominent eosinophils between collagen bundles. Sweet syndrome, also known as acute febrile neutrophilic dermatosis, is characterized by dermal edema and a dense neutrophilic infiltrate, associated with a constellation of clinical and biological signs. We describe herein 2 cases of arthropod bite reactions with impressive clinical lesions and histopathological findings reminiscent of Sweet syndrome. However, the patients were lacking other criteria for Sweet syndrome and were diagnosed as Sweet-like reaction to arthropod bites. Pathologists should be careful in rendering a diagnosis of neutrophilic dermatosis, which requires clinicopathological correlation, and should consider arthropod bite reactions in the differential diagnosis.