PURPURIC LESIONS are the clinical expression of the passage of erythrocytes from the vascular compartment to the extravascular one, generally following damage related to permeabilization of the walls of small vessels. At times, they are the only clinical feature, at other times the sign of a more complex morbid process and the expression of a serious condition, as in the systemic vasculitides.

The clinical spectra of vasculitides are broad, with a variety of conditions ranging from mainly cutaneous involvement with a relatively benign course, such as leukocytoclastic vasculitis, to situations in which the cutaneous involvement is less evident but an integral part of a process that could progress to a critical situation requiring emergency treatment. Acute pulmonary insufficiency or renal blockage, as an expression of a systemic vasculitis, is relatively frequent in intensive care units. Central and peripheral nervous system involvement, cardiac failure, and intestinal ischemia, as complications or first presenting signs of systemic vasculitides, are clinical conditions commonly encountered in current practice. Purpura fulminans (PF), often associated with disseminated intravascular coagulation (DIC), is a dramatic condition that must be identified correctly and differentiated from purpura simplex.