Imported fire ant envenomation: A clinicopathologic study of a recognizable form of arthropod assault reaction

Abstract

In biopsies taken in a clinical setting, even in the absence of the characteristic subepidermal pustule, the diagnosis of imported fire ant sting can be suspected if there is a superficial and deep perivascular, periadnexal and interstitial infiltrate composed of neutrophils, with some basophilic denaturation of collagen.

Using reflectance confocal microscopy to visualise neutrophilic infiltrate in fire ant stings

“…Clinically, the initial reaction from a sting is a 25–50 mm dermal flare, with wheal development within minutes and pustule development within hours 4 7. These pustules transform into clear fluid filled vesicles within 4 hours and then cloudy fluid filled vesicles within 8 hours, indicating infiltration of inflammatory cells.…”

“…Pathophysiology of the allergic response involves venom allergens processed by antigen-presenting cells and subsequent T cell activation 6. Neutrophils are recruited to the sting site via inflammatory cytokines 7. Eosinophils are seen in later-phase reactions, most likely due to a Th2-mediated mechanism 2 4.…”

“…The varying refractive indices of different cellular components will produce varying brightness. This imaging method can penetrate up to 250 nm, meaning we can visualise the papillary dermis and upper reticular dermis 7. The lens is placed directly on the skin with use of an immersion oil and can produce images comparable to using a 30× objective 8.…”

“…6 Neutrophils are recruited to the sting site via inflammatory cytokines. 7 Eosinophils are seen in later-phase reactions, most likely due to a Th2-mediated mechanism. 2 4 Although histopathological examination has demonstrated that neutrophils are involved in the physiological reaction to fire ant stings 4 7 this has not been demonstrated in vivo, to our knowledge.…”

“…This imaging method can penetrate up to 250 nm, meaning we can visualise the papillary dermis and upper reticular dermis. 7 The lens is placed directly on the skin with use of an immersion oil and can produce images comparable to…”