Skin involvement in cutaneous and systemic vasculitis

Cutaneous vasculitides are a heterogeneous group of inflammatory disorders affecting skin blood vessels. They may be triggered by several factors, such as infection or drug, or may be related to underlying disease, notably connective tissue or malignancies. However, vasculitis occurs without any demonstrable triggering agents in a relevant number of patients. On the other hand, vasculitic skin lesions may manifest as a component of vasculitis affecting also internal organs; in someone of these patients, skin involvement occurs initially as the sole sign of disease, leading to consider cutaneous vasculitis a diagnosis of exclusion. In this review, we have focused on the most common variants of cutaneous vasculitis, including cutaneous small vessel vasculitis and urticarial vasculitis as well as Henoch–Schönlein purpura, a systemic form in which however skin involvement often predominates. We have also argued on livedoid vasculopathy, a cutaneous entity which, although nonfrankly vasculitic in origin, is frequently associated with connective tissue disease. Finally, we have analyzed the variety of cutaneous manifestations that may develop during the course of the main systemic vasculitides, such as Wegener's granulomatosis, Churg–Strauss syndrome and polyarteritis nodosa.