We describe 5 cases of tick bite reactions with dermal necrosis and sparse interstitial to dense diffuse dermal neutrophilic infiltrates associated with thrombogenic vasculopathy. Tick bite reactions classically consist of moderately dense perivascular infiltrates composed of an admixture of inflammatory cells. Each of our patients had embedded tick parts, with interesting histologic features.
Ticks are ectoparasites that cause dermatologic disease both directly through physical trauma to the skin, salivary secretions, or remnant body parts, and indirectly through transmission of disease. Lyme disease, Rocky Mountain spotted fever, tularemia, and babesiosis are known tick‐transmitted diseases. The histopathology related to a primary tick bite, similar to other arthropod bites, classically consists of a perivascular infiltrate composed of lymphocytes, neutrophils, histiocytes, plasma cells, and eosinophils in varying amounts. We describe five patients with a novel histologic reaction to embedded tick parts., Each case demonstrates a thrombotic vasculopathy consisting of intraluminal eosinophilic deposits that stain strongly with Periodic acid Schiff stain. The adjacent tissue shows dermal necrosis with surrounding interstitial to diffuse dermal neutrophilic inflammation. We postulate that diffuse dermal nutrophilic infiltrates in association with thrombogenic vasculopathy is an unusual histologic picture of tick bite reactions that may be attributable to remnant tick parts.
