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© Dirk Biddle
The vasculitides have traditionally been classified by the nature of the disease process itself (i.e. as a primary or as secondary disease process), by their broad pattern of clinical features, including vessel size (e.g. small, medium or large) and type (e.g. venous, arterial or lymph), or by their histopathological features such as the character of the inflammatory infiltrate (e.g. the type of leucocyte or the type of antibody present at the site of inflammation). More recently advances in our understanding of genetic and immunopathogenic mechanisms offer additional classification and diagnostic tools (e.g. the different types of inflammatory or autoimmune reaction that are triggered in genetically susceptible individuals).
There are also some general classificatory terms used to describe the various vasculitides that the reader should take note of for future reference. For example Polyarteritis Nodosa (PAN) may be described as a systemic necrotising vasculitis that affects small-to-medium arteries, while Takayasu’s arteritis (TA) is a systemic granulomatous large vessel arteritis that primarily affects the aorta, its major branches to the extremities.
Systemic vasculitis: a very general term simply meaning any vasculitis condition characterised by inflammation of vessels in multiple sites in the body and which share many clinical features.
Idiopathic vasculitis: any vasculitis condition arising from an unknown cause (as distinct from having “no cause”).
Cutaneous vasculitis: any vasculitis condition primarily relating to or affecting the skin.
Necrotising vasculitis: any vasculitis condition causing the death of living tissues.
Granulomatous vasculitis: any vasculitis condition causing a mass or nodule of chronically inflamed tissue characterised by a large number of cells of various types (macrophages, lymphocytes, fibroblasts, giant cells, etc), some degrading and some repairing the tissues.
Leukocytoclastic vasculitis: a cutaneous acute vasculitis characterised clinically by palpable purpura, especially of the legs, and histologically by exudation of the neutrophils and sometimes fibrin around dermal venules, with nuclear dust and extravasation of red cells; may be limited to the skin or involve other tissues.
Lymphocytic vasculitis: any vasculitis condition mediated by cells originating in lymphoid tissues such as the thymus or specific types bone marrow (eg; B-cells, T-cells).
Eosinophilic vasculitis: any vasculitis condition mediated by leucocytes (white blood cells) that stain brightly purple with eosin dyes (e.g. eosinophils or neutrophils).
Fuller definitions of these vasculitis terms can be found later in this article.
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