Investigations by direct immunofluorescence and electron microscopy seem to have produced contradictory results. All authors noted, however, that fibrin deposits were present in the vessel walls and thrombi in the lumina of some vessels, those findings corresponding well to features histopathologic said to be typical of LV. That amounts of immunoglobulins and complement factors varied among patients observed by different authors may indicate that these deposits are a consequence of the disease process rather than the cause of it.