The Vasculitides

© Dirk Biddle

1.3.2 Vessel Size and the Chapel Hill Consensus Conference

The most widely accepted approach to vasculitis disease classification is that taken by the 1992 Chapel Hill Consensus Conference on the Nomenclature of Systemic Vasculitis (2). This classification system primarily divides the vasculitides according to the size of the blood vessel involved: large (the aorta (The large arterial trunk that carries oxygenated blood from the heart to be distributed by branch arteries through the body to the extremities, neck and major organs. It is the largest artery in the body.)and its major branches), medium-sized (the main visceral (Viscera:Plural of viscus:An internal organ of the body, especially one located in the large cavity of the trunk (such as the heart, liver, or intestine). (M+))arteries) and small (arterioles (Arterioles: A minute artery, especially one that leads to a capillary. (OMD)), capillaries (Capillaries:Any of the smallest blood vessels connecting arterioles with venules and forming networks throughout the body. (M+)and venules(Venules:Any of the minute veins connecting the capillaries with the larger systemic veins. (M+))).

According to the Chapel Hill Consensus Conference large-vessel vasculitides include Giant cell arteritis and Takayasu’s arteritis; medium-sized vessel vasculitides include Polyarteritis nodosa and Kawasaki disease; and small-vessel vasculitides include Churg-Strauss syndrome, (Essential) Cryoglobulinemia, Cutaneous leukocytoclastic angiitis, Henoch-Schönlein purpura, Microscopic polyangiitis, and Wegner’s granulomatosis (1).

However useful this classification system may be, it is somewhat limited. For example, it does not take into consideration other well recognised primary vasculitides such as Behcet disease (affecting small, medium and large vessels), Buerger’s disease (small vessels), CNS vasculitis (small to medium vessels), and Polymyalgia rheumatica (small vessels); nor does it account for any of the secondary vasculitis conditions such as Cogan's syndrome (small, medium and large vessels), Chronic venous insufficiency (small to medium vessels), Drug-induced vasculitis (primarily small, but can include medium and large vessels), Relapsing polychondritis (small to medium vessels), Rheumatoid vasculitis (small vessels), Scleroderma (small to medium vessels), Serum sickness (small vessels), Sjögren's syndrome (small to medium vessels), Systemic Lupus Erythematosus (small vessels) and Urticarial vasculitis (small vessels). Further, there is often a great deal of overlap within and between the vasculitides regarding the size of vessels involved.

It would however be misguided to dismiss the Chapel Hill system based on the above criticisms - the Conference went much further. The following presents an excerpt from some of the conclusions and proposals made at the 1992 Chapel Hill Consensus Conference and it is presented here in order that the reader may recognise more fully the utility of the Chapel Hill system - as it goes beyond mere classification. Much of the terminology may be unfamiliar to the reader at this point, but will be clarified in later sections.

  1. Although not a prerequisite component of the definitions, patient age is recognized as a useful discriminator between Takayasu arteritis and giant cell (temporal) arteritis.
  2. The name "polyarteritis nodosa," or alternatively, the name "classic polyarteritis nodosa," is restricted to disease in which there is arteritis in medium-sized and small arteries without involvement of smaller vessels. Therefore, patients with vasculitis affecting arterioles, venules, or capillaries, including glomerular capillaries (i.e., with glomerulonephritis), are excluded from this diagnostic category.
  3. The name "Wegener's granulomatosis" is restricted to patients with granulomatous inflammation. Patients with exclusively nongranulomatous small vessel vasculitis involving the upper or lower respiratory tract (e.g., alveolar capillaritis) fall into the category of microscopic polyangiitis (microscopic polyarteritis).
  4. The term "hypersensitivity vasculitis" is not used. Most patients who would have been given this diagnosis fall into the category of microscopic polyangiitis (microscopic polyarteritis) or cutaneous leukocytoclastic angiitis.
  5. The name "microscopic polyangiitis," or alternatively, "microscopic polyarteritis," connotes pauci-immune (i.e., few or no immune deposits) necrotizing vasculitis affecting small vessels, with or without involvement of medium-sized arteries. Cryoglobulinemic vasculitis, Henoch-Schonlein purpura, and other forms of immune complex-mediated small vessel vasculitis must be ruled out to make this diagnosis.
  6. The name "cutaneous leukocytoclastic angiitis" is restricted to vasculitis in the skin without involvement of vessels in any other organ.
  7. Mucocutaneous lymph node syndrome must be present to make a diagnosis of Kawasaki disease (2).

It is notable then that vessel size was not the only criterion on which the Chapel Hill Conference reached consensus. Nevertheless, given the above, it is apparent that criteria other than vessel size do become necessary in aiding precise classification and diagnosis of the many vasculitides.

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1. Jennette, J., Falk, R., Andrassy, K., Bacon, P., Churg, J., Gross, W., Hagen, E., Hoffman, G., Hunder, G., Kallenberg, C., et al. (1994) Nomenclature of systemic vasculitides. Proposal of an international consensus conference. Arthritis Rheumatica, 37(2), 187-92.

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