Structural and ultrastructural evidence regarding immunologically mediated-pathogenesis in mucosal lichen planus.

Tissue samples from six patients suffering from lichen planus (L. P.), with oral and genital localization were examined by light and transmission electron microscopy, in order to better define the structural and ultrastructural changes that are correlated with L. P. and fit with immunologically mediated pathogenesis theory. Many of the classical histopathological features of L. P. were found: the hydropic degeneration of basal keratinocytes, presence of colloid bodies and heavy chronic chorionic inflamatory cell infiltrate. There were also observed several differences from skin localization of L. P. consisting in more frequent parakeratosis, obvious atrophy of the epithelium, pathological presence of granular layer. Ultrastructural studies confirm and clarify the light microscopic picture: basal lamina is frequently broken, basal keratinocytes are degenerated, presenting thickening, clumping and disorders of orientation of tonofilaments. There are many Langerhans cells. The inflammatory infiltrate is composed of interacting cells: many T-lymphocytes and activated macrophages, few B-lymphocites and plasma cells.