Introduction

Vasculitic disorders develop from inflammation of the blood vessels (vasculitis). Vasculitis commonly occurs in disorders that affect connective tissue, but it can also occur in conditions that do not affect connective tissue. Vasculitis is not a disease but rather a disease process.

Usually the triggers of vasculitis are not known. However, certain viruses, especially hepatitis viruses, can initiate it. Other triggers appear to be certain infections and reactions to certain drugs and vaccines. Presumably, the inflammation occurs when the immune system mistakenly identifies blood vessels or parts of a blood vessel as foreign and attacks them. Cells of the immune system, which cause inflammation, surround and infiltrate the affected blood vessels, damaging them and possibly damaging the tissues they supply. The damaged blood vessels may become leaky or clogged; either way, blood flow to the areas supplied by the damaged vessels is disrupted. The areas deprived of blood (ischemic areas) can be damaged permanently. Symptoms may result from direct damage to the blood vessels or from indirect damage to tissues (such as nerves or organs) whose blood supply has been disrupted.

Any blood vessel may be affected. Vasculitis may be limited to veins, large arteries, small arteries, or capillaries, or it may be limited to vessels in one part of the body, such as the head, leg, or kidney. Disorders such as Henoch-Schönlein purpura, erythema nodosum, polyarteritis nodosa, temporal (giant cell) arteritis, and Takayasu's arteritis are characterized by vasculitis that is limited to blood vessels of a particular size or depth.

See the table Selected Disorders Characterized by Vasculitis.