[Cutaneous alterations in vasculitides : Part 1: Nomenclature, classification and correlation between clinical signs and histological features].

The skin is one of the organs most commonly affected by vasculitis and the only one that is open to direct inspection. Cutaneous vasculitis can be part of a systemic vasculitis, a variant restricted to the skin (e.g. systemic and cutaneous IgA1 vasculitis) or an independent cutaneous form (recurrent macular vasculitis in hypergammaglobulinemia, nodular vasculitis). For the nomenclature and classification of cutaneous vasculitides the scheme of the Chapel Hill Consensus Conference can be used and the vessels mainly affected determine the clinical picture of individual forms of vasculitis. Some cutaneous efflorescences and their distribution are so characteristic for certain forms of vasculitis that they provide diagnostic indications or even diagnostic criteria. A palpable purpura on the legs is typical for involvement of postcapillary venules in the context of immune complex vasculitis. If arterioles or venules in the dermis are additionally affected, the clinical presentation is that of plaques with marginal offshoots and central hemorrhagic blisters or necrosis (retiform purpura). In contrast to the purpura in occluding vasculopathies, which shows no or little surrounding erythema, the purpura in vasculitis is accompanied by an inflammatory erythema. In vasculitides of the arterioles and small-caliber arteries in the subcutaneous tissue, visible or only palpable nodules exist surrounded by an irregular livedo or also retiform purpura. Understanding how vasculitis-induced efflorescence arises and the histological manifestations helps their recognition during physical examinations in daily practice and is an important guide in the diagnosis and classification of vasculitides.