Vasculitis would be the inflammation of a blood vessel. It is associated with a number of diseases including Henoch-Schonlein Purpura.

Swelling of blood vessels can be caused by any number of things. If they rupture from the swelling, bruises will form, if not, the skin in effected areas will likely appear very red and tender.

Vasculitis is often painful, and can cause internal hemorrhaging quite easily.