[Electronmicroscopic studies on allergic vasculitis]

Electron microscopic investigations were carried out on cutaneous lesions of different morphological appearances in 8 cases of vasculitis allergica Ruiter. The endothelial damages observed (defoliating, vacuolisation, forming of microvilli and bizarre membrane structures within the lumen, interruption of the endothelial continuity) put the question for participating of a Shwartzman phenomenon. The multilayered formation of the basement membrane or their homogeneous spreading may be a sequence of damage and a compensation phenomenon. It is quite possible that filamentous structures, being within the basal cytoplasm of the endothelial cells, represent immune-complexes. During the necrobiotic phase, the perivascular infiltrates partly consists of leucocytes, fibrin, and debris, and during the later phagocytotic phase, the infiltrates partly consists of lymphocytes and histiocytes (macrophages). The findings are explained as morphological substratum of the Arthus-reaction.