Vasculitis
What Is Vasculitis?
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), or
- 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?
Vasculitis can be caused by
- infection of the blood vessel walls
- This is rare. When it occurs, bacteria, viruses or fungi infect the blood vessel.
- 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 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.