The color of skin: purple diseases of the skin, nails, and mucosa.

The color purple can be seen in several types of eruptions including inflammatory dermatoses like lichen planus, infectious dermatoses like ecthyma gangrenosum, neoplasms like Kaposi sarcoma, and vasculitis and vasculopathy. The current review focuses on the clinical appearance, pathophysiology, and treatment of several vasculitides and vasculopathies including capillaritis, cutaneous small-vessel vasculitis, immunoglobulin A (IgA) vasculitis, cryoglobulinemia, granulomatosis with polyangiitis, eosinophilic granulomatosis with polyangiitis, microscopic polyangiitis, polyarteritis nodosum, warfarin-induced skin necrosis, heparin-induced thrombocytopenia, purpura fulminans, antiphospholipid antibody syndrome, calciphylaxis, levamisole-induced vasculopathy, and thrombotic thrombocytopenic purpura. Dermatologists play a central role in treating patients with cutaneous vasculitis and vasculopathy and may have the opportunity to facilitate identification of systemic disease by diagnosing cutaneous vasculitis and vasculopathy.