Cutaneous allergic vasculitis: clinicopathological characterization and identification of apoptosis

To elucidate the clinicopathological features of cutaneous allergic (leukocytoclastic) vasculitis (CAV), biopsied skin tissues of 32 patients with CAV were examined immunohistopathologically and compared with the main clinical features. Additionally, to obtain some clues to better understand the roles of infiltrating cells, particularly neutrophils in CAV, apoptosis and related antigens were investigated in vivo. The 32 patients with CAV were divided into two groups based on their clinical course: (i) non-recurrent (group I; nine cases); and (ii) recurrent (group II; 23 cases). Immunohistopathologically, group I was characterized by stereotypical necrotizing changes of CAV with fibrin exudation of small blood vessels in the upper cutis, and group II was characterized by CAV and fibrous thickening of the vascular walls with significant infiltration of CD3+, UCHL-1+ T cells. Group II was subdivided further: groups IIa (15 cases) and IIb (eight cases); that is, the former was notable for necrotizing changes of CAV, which tended to spread into the proper corium down to the lower cutis; whereas the latter exhibited considerably less marked histological changes of CAV without any spread to the lower cutis. In a comparison of the clinical data among the three groups, there were considerable differences in age, clinical course, localization of purpura and associated disease. In particular, group II showed a high frequency of connective tissue diseases. The presence of apoptosis was seen in a considerable number of neutrophils, and some nuclear debris turned out to be apoptotic bodies by the in situ terminal deoxytransferase (TdT)-catalyzed DNA nick end-labeling (TUNEL) method and electron microscopy. By combining immunohistochemistry with TUNEL, the majority of apoptotic neutrophils and nuclear debris was seen to be ingested by macrophages. In immunohistochemical examinations for apoptosis-related bcl-2 protein and Fas antigen, bcl-2 was recognized only in the cytoplasm of infiltrating T cells, and Fas was positively stained on the cellular membranes of infiltrating T cells and neutrophils in a scattered fashion. Thus, a novel method for neutrophil disposal in CAV was suggested.