Abstract:

Ticks are a well-known vector for viral and bacterial infections, many of which are accompanied by cutaneous eruptions. The bite itself can induce a spectrum of inflammatory reactions, including dermal infiltrates of neutrophils, eosinophils, histiocytes, and lymphocytes, as well as vascular thrombi, extravasation of erythrocytes, and neutrophil damage to blood vessels consistent with small vessel vasculitis. The present case demonstrates a unique histopathological reaction to embedded tick part remnants inducing a localized medium vessel vasculitis. A 68-year-old man from Rhode Island presented to clinic with a tick bite on his left thigh. The bite site appeared as an eroded and crusted 4 mm papule with visible embedded tick part remnants and surrounding erythema. On histology, sections show retained tick part remnants superficially along with a wedge-shaped inflammatory reaction composed of lymphocytes and neutrophils. Interestingly, beneath the tick parts was a medium caliber vessel showing clear evidence of vasculitis, including disruption of the vessel wall by lymphocytes and neutrophils along with deposition of fibrin and nuclear debris within the vessel wall. In addition to the known leukocytoclastic and cryoglobulinemic vasculitides, thought to be induced by the secretory products of the ticks saliva, tick bites may also generate a localized medium vessel vasculitis as demonstrated in this case. Given the focal nature of the vessel damage, this case represents an example of secondary vasculitis without need for immunosuppressive therapy. However, prophylactic coverage for Lyme was indicated. It is important to recognize the histology associated with tick bite response in order to prevent misdiagnosis and potential over-treatment of a vasculitic condition. Dermatologists and pathologists should consider medium vessel vasculitis as a possible histopathologic change observed in localized tick bite reactions, with or without evidence of tick part remnants.

Financial Disclosure:
No current or relevant financial relationships exist.

Menu

Shauna Rice, BS