Vasculitis is an inflammation of the blood
vessels. Inflammation is a condition in which tissue is
damaged by blood cells entering the tissues. In
inflammatory diseases, these cells are mostly white blood
cells. White blood cells circulate and serve as our major
defense against infection.
Ordinarily, white blood cells destroy bacteria and viruses.
However, they can also damage normal tissue if they invade
it.
Vasculitis can affect
-very small blood vessels (capillaries),
-medium-size blood vessels (arterioles or venules),
-large blood vessels (arteries or veins).
How Does Vasculitis Damage The Body?
Several things can happen to an inflamed blood vessel.
If it is a small vessel, it may break and produce tiny areas
of bleeding in the tissue. These areas will appear as small
red or purple dots on the skin.
If a larger vessel is inflamed, it may swell and produce a
nodule which may be felt if the blood vessel is close to the
skin surface. The inside of the vessel tube may become
narrowed so that blood flow is reduced. The inside of the
vessel tube may become totally closed, usually by a blood
clot which forms at the site of inflammation.
If blood flow is reduced or stopped, the tissues which
receive blood from that vessel begin to die.
For example, a person with vasculitis of a medium-sized
artery in the hand may develop a cold finger which hurts
whenever it is used. Occasionally this can progress to
gangrene.
What Causes Vasculitis?
-Infection of the blood vessel walls This is rare.
When it occurs, bacteria, viruses or fungi infect the
bloodvessel. White blood cells move in to destroy the
infectious agents and damage the
blood vessel in the process. This is a serious condition and
requires prompt antibiotic treatment.
-An immune or "allergic" reaction in the vessel walls. This
cause of vasculitis is more common.
Substances which cause allergic reactions are called
antigens. Antigens cause the body to make
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proteins called antibodies which bind to the antigen for the
purpose of getting rid of it. Antigen and antibody bound
together are called immune complexes.
Two primary ways in which immune complexes destroy antigens are:
-by attracting white blood cells to digest the antigen
-by activating other body substances to help destroy the antigens.
Unfortunately, some immune complexes do not serve their purpose of
destroying antigens. Instead, they remain too long in the body and
circulate in the blood and deposit in tissues. They commonly
accumulate in blood vessel walls, where they cause inflammation. It
is likely that some white blood cells (cytotoxic cells) which kill
infectious agents can also accidentally damage blood vessels and
cause vasculitis.
Vasculitis Caused By Lupus
In these cases, the antigens causing the immune complexes
are often not known. In some cases, the complexes contain DNA and
anti-DNA antigens, or Ro (also called SS-A) and anti-Ro antigens. A
recently discovered antibody, ANCA (anti-neutrophil cytoplasm
antibody), can cause vasculitis in some individuals.
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