Cutaneous manifestations of vascular disorders can range from a mild rash to urticaria, vasculitis, erythema multiforme major, or to anaphylaxis. Vasculitis includes those disorders that feature inflammation of blood vessel walls and can affect various organ systems. The vast majority of vasculitic dermatologic disorders involve the smaller blood vessels in the skin; less often, large and medium vessels may be involved. In this chapter the discussion will be limited to those vasculitides that involve the smaller blood vessels. The differential diagnosis of vasculitis is broad and includes vasculopathic disorders such as cryoglobulinemia, Waldenstrom macroglobulinemia and Churg-Strauss syndrome.

Purpuric lesions can be a sign or symptom of vascular disorders such as coagulopathies or vasculitis and can also serve as clues to systemic diseases such as systemic lupus erythematosus. Of lesser concern are the so-called “benign” variants—the benign pigmented purpuras (BPPs) that are caused by capillaritis, which allows blood to exit small vessels (extravasation) and create petechiae. As their name implies, BPPs are not associated with any systemic disease.