Presence and interpretation of vascular immune deposits in human skin: the value of direct immunofluorescence.

Direct immunofluorescence investigation of the skin is an easy and valuable technique to establish the diagnosis immune complex vasculitis. Vascular immune deposits can be found in 60-80% of all cases. Absence of vascular immune deposits, however, does not exclude vasculitis per se, since the dynamics of the vasculitic process limit their presence in time. Knowledge of these dynamics is indispensable for both the clinician and the interpreter. Several practical options are discussed that may increase sensitivity. The specificity of vascular immune deposits has become a complex matter. Different immunoglobulin classes have different specificity, indicating that specificity also depends on the relative incidence of individual immunoglobulin classes. Some of these relative incidences seem to have changed over the years. Furthermore, several non-vasculitic diseases and conditions have now been described, that may show fluorescent pictures similar to vasculitis and thus decrease specificity.