Local reactions to tick bites.
A retrospective histological and immunohistochemical study has been carried out in 25 cases of tick bites recorded in our Departments. The samples that included an attached tick showed a cement cone anchoring the mouthparts to the skin and a blood-soaked, spongiform appearance of the superficial dermis, with a mild neutrophilic and eosinophilic infiltration. The vessels displayed a loose multilayered endothelial proliferation, with plump endothelia, permeated with erythrocytes. A few of them were severed, allowing copious blood extravasation. The established lesions included the following: erythema chronicum migrans-like cases, foreign body granulomas-sometimes containing remnants of the mouthparts-cutaneous lymphoid hyperplasia, either of the T-cell or the B-cell type, and tick-bite alopecia. In both the T-cell and B-cell pseudolymphomas, several vessels showed concentric endothelial and perithelial proliferation similar to that seen in the acute lesions. In the tick-bite alopecia, a lymphocytic infiltrate attacked the permanent portion of the hair follicles, whose reaction was a noticeable hyperplasia of the fibrous sheaths, although only a minority of the hairs was destroyed. The observed alterations are specific in the acute lesions and in the alopecia, where they directly arise as a result of the interactions between the host's tissues and the antihemostatic, anti-inflammatory, and immunomodulatory chemicals contained in the tick saliva. In the other lesions, the changes seem less characteristic, although the fragments of mouthparts and the special vascular changes provide a clue to their etiology.
Castelli
Elena
E
Department of Dermatology, University of Palermo, Palermo, Italy. sansoknife@tin.it
Caputo
Valentina
V
Morello
Vincenza
V
Tomasino
Rosa Maria
RM
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000506:Alopecia Areata / Q000469:parasitology / Q000473:pathology; D000818:Animals; D001402:B-Lymphocytes / Q000473:pathology; D002648:Child; D015787:Erythema Chronicum Migrans / Q000469:parasitology / Q000473:pathology; D005260:Female; D006790:Host-Parasite Interactions; D006801:Humans; D007299:Insect Bites and Stings / Q000150:complications / Q000473:pathology*; D018884:Ixodes; D008297:Male; D008875:Middle Aged; D019310:Pseudolymphoma / Q000276:immunology / Q000473:pathology; D012189:Retrospective Studies; D012871:Skin Diseases / Q000276:immunology / Q000469:parasitology / Q000473:pathology*; D013601:T-Lymphocytes / Q000473:pathology