The histopathology of pathergy: a chronologic study of skin hyperreactivity in Behcet's disease

Background many patients with Behcet's disease (BD) demonstrate hyperreacti vity (pathergy), and the induced skin lesions may serve as a model for the disease. Objective This study examined the sequence of histopathologic changes after needle prick trauma. Methods Eight patients fulfilling the International Study Group Criteria fo r Behcet's Disease, two patients with recurrent aphthous stomatitis, and tw o healthy controls each underwent intradermal injections with subsequent bi opsies at 0, 4, 24, and 48 h. Hematoxylin and eosin sections were evaluated in a blinded fashion according to 11 histopathologic criteria. Results At time zero, normal skin was seen. By 4 h, neutrophils were presen t usually admired with lymphocytes (8 out of 10). The inflammatory cell den sity peaked by 24 h in 8 out of 10 patients and at 48 h in 2 out of 10 pati ents. Sparse leukocytoclasis was identifiable from 4 to 48 h, but was not a ssociated with fibrin, True vasculitis (as evidenced by fibrin within vesse l walls and/or intraluminal thrombi) was not seen, Intraepidermal pustules (IEPs) and polymorphonuclear (PMN) aggregates within the needle tract were seen as early as 4 h. The control patients and three out of eight of the ED patients failed to develop clinical lesions. Among this group histopatholo gic IEPs were lacking in all but two ED patients. Conclusions These data suggest that early pathergy is mediated by PMNs and lymphocytes without vasculitis. Hyperchemotaxis may explain the rapid accum ulation of PMNs along the injection site.