Vasculitis is what? Where? Why?

Why ask why? Vasculitis is defined by the presence of inflammatory white blood cells in blood vessel walls with reactive damage to mural structures. This can lead to bleeding and ischemia/necrosis downstream of the vessel. Affected vessels vary in size, type, and location in association with the specific type of vasculitis. There are many different types. The exact mechanisms underlying them are unknown.
Vascular Swelling. Vasculitis refers to a localized or generalized process of inflammation in the cells that make up our blood vessels. It can involve the veins (phlebitis) or the arteries (arteritis). Both are serious and can lead to clot formation which is also dangerous if the clot migrates. Since the condition can occur with another illness or by itself, it requires appropriate recognition and prompt care.