Cutaneous pseudovasculitis.

Cutaneous pseudovasculitis represents a heterogeneous collection of disorders that are capable of simulating cutaneous vasculitis and can be broadly classified into diseases that produce hemorrhage (petechiae, purpura, and ecchymoses) or vessel occlusion with resultant livedo, cyanosis, ulcers, digital necrosis, and/or gangrene. Overlap is not uncommon, but if present, one mechanism dominates. Hemorrhagic pseudovasculitis is due to vessel wall dysfunction (incompetence), which can be related to diverse factors that include vessel wall deposition of metabolic substances (amyloid, calcium), nutritional deficiencies (scurvy), nonvasculitic inflammatory purpura (pigmented purpuric dermatitis, arthropod, viral and drug reactions), degeneration of the vessel wall and supporting stroma (senile/solar purpura), direct vessel wall invasion of infective organisms, coagulation-fibrinolytic disorders (eg, thrombocytopenia), and vessel wall trauma. Cyanotic-infarctive pseudovasculitis is due vaso-occlusion by emboli, thrombi, or fibrointimal hyperplasia (endarteritis obliterans) and includes varied conditions such as purpura fulminans, Coumadin necrosis, antiphospholipid antibody syndrome, cardiac myxoma, cholesterol embolization, calciphylaxis, and radiation arteritis. Delayed and inappropriate diagnosis of pseudovasculitis leads to incorrect management and exposure to potentially deleterious treatment modalities such as corticosteroids and cytotoxic agents. The diagnosis of a pseudovasculitic disorder requires a high index of suspicion and should always be part of the differential diagnosis of vasculitis. Skin biopsy is a crucial step in differentiating pseudovasculitis from authentic vasculitis; absence of histologic evidence of vasculitis, particularly after multiple biopsies, should direct evaluation and diagnosis towards pseudovasculitis.