VASCULITIS is an inflammatory disorder of blood vessels that can affect both the arterial and venous limbs of the vascular tree. The process is often segmental, and it can affect vessels of all sizes. It is characterized histologically by infiltration of the affected vessel wall by neutrophils or mononuclear cells, local destruction of the vessel wall, extravasation of red blood cells into surrounding tissue, fibrinoid necrosis, and thrombosis. Immunofluorescent microscopy often demonstrates the presence of immunoglobulin(s), complement component(s), and fibrin deposited in the vessel wall. The outcome of the vasculitic lesion is often infarction and necrosis of tissue distal to the site.1 Diagnosis of vasculitis is confirmed by identification of the pathognomonic histological lesion.
Under many clinical circumstances, however, it is not feasible to obtain tissue for histopathology. This is the situation, for example, in isolated central nervous system vasculitis, wherein a cortical or leptomeningeal biopsy might not be