Ultrastructure of lymphocyte-mediated fat-cell lysis in erythema nodosum-like lesions of Behçet's syndrome.

In this study, biopsy specimens from 18 patients with Behçet's syndrome were examined by electron microscopy with particular attention to the appearance of the lymphocyte-macrophage infiltrate into the interlobules of subcutaneous fat in erythema nodosum-like lesions. Electron microscopic evaluation revealed vacuolization changes of fat cells with detachment of their cell membrane from the basal lamina that permitted lymphocytes and macrophages to enter into this developed space. We believe that the detachment of fat cells from the basal lamina precedes invasion by lymphocytes which, in turn, attracts macrophages into the space. This eventually leads to fat-cell lysis accompanied by activation of macrophages, which causes further inflammation, completing the picture of panniculitis in the erythema nodosum-like lesions in Behçet's syndrome.