Single organ cutaneous vasculitis: Case definition & guidelines for data collection, analysis, and presentation of immunization safety data

Vasculitides are a group of heterogeneous conditions character- ized by inflammation of blood vessel wall, which can occur in any organ system. Cutaneous involvement occurs almost exclusively with vasculitis of small and medium-sized vessels [1]. Cutaneous vasculitis (CV) may be: (a) a single organ disease limited to the skin, (b) primary CV with secondary systemic involvement, or (c) a cutaneous manifestation of systemic vasculitis [1]. Several classifications and definitions have been proposed for vasculitides, for example those published by the American College of Rheumatology and the Chapel Hill Consensus Conference (CHCC), but they all have various limitations [2–4]. The prolifera- tion of names for CV is principally due to the fact that various dis- orders can be associated with small-vessel vasculitis of the skin: sometimes it is only cutaneous and in other cases there can be other organ involvement [5]. In 1952, upon the first classification, the term ‘‘hypersensitivity vasculitis” (HV) was coined to distinguish forms of necrotizing arteritis of small vessels from polyarteritis nodosa (PAN), which involved larger vessels. HV derives its name from animal models of vasculitis induced by horse serum or drug administration to cause hypersensitivity reactions [5]. Subsequently, the term has been refined to denote small vessel vasculitis confined mainly to the skin and not associated with any other primary vasculitis (i.e. Henoch-Schoenlein purpura, granulomatosis with polyangiitis or cryoglobulinemia). The 1994 CHCC proposed an alternative term for HV - ‘‘cutaneous leukocytoclastic angiitis” because of the fre- quent failure to identify a precipitant factor for hypersensitivity reaction. This term was also problematic because histological fea- tures were not always consistent with this clinical phenotype [5]. The more comprehensive definition of cutaneous small vessel vas- culitis (CSVV), which includes clinical and histological features of HV and leukocytoclastic vasculitis irrespective of a possible trig- gering factor is also used. More recently, the 2012 revised CHCC nomenclature recommended that for single organ vasculitis, which is applied to vasculitis in arteries or veins of any size in a single organ that has no features that indicate that it is a limited expres- sion of a systemic vasculitis, the involved organ and vessel type should be included in the name (e.g. cutaneous small vessel vas- culitis) [4]. Therefore, for this case definition we adopted the term single organ cutaneous vasculitis (SOCV), which refers to small vessel vasculitis of the skin where systemic involvement has been excluded.