Purple Brain Fever

Purple Brain Fever is a mysterious disease, and seems to afflict single victims out of the blue. At first it makes the victim light-headed so it is difficult to concentrate. Then the victim’s flesh puff s up and turns dark purple. His tongue expands to fill his mouth, making it hard to even breathe and almost impossible to eat. Other limbs bloat and sometimes even fall off. The head swells so the eyes can hardly see. Death comes as a merciful release.

Source
pg. 13
 * Warhammer Fantasy RPG 3rd ED -- Book of Plague