The effects of silica on lymph nodes and vessels--a possible mechanism in the pathogenesis of non-filarial endemic elephantiasis.

Non-filarial tropical elephantiasis, which occurs in certain volcanic areas of the world, has been postulated to be an obstructive lymphopathy due to the fibrogenic effects of silica absorbed through the plantar skin of bare-footed people. Animal experiments involving the direct intralymphatic injection of fine silica particles have been carried out in order to assess the extent to which this substance can engender lymphatic obstruction and to determine its main site of action. Intralymphatic silica provoked an immediate and intense macrophage reaction with later fibrosis both within lymph vessels and to a lesser extent within lymph nodes. Lymphography indicated that the consequent obstruction resulted more from the effects of silica on vessels than on nodes.