A tumor of the walls of small blood vessels. Usually appearing as pink to purple painless spots called lesions on the legs or arms, KS may also occur internally. Death occurs from major organ involvement. Originally seen in older men of Mediterranean or Ashkenazi Jewish descent late in life and young men from equitorial Africa, KS is now occurring in young men, 80 percent of whom are gay or bisexual, and is a much more agressive disorder in persons with AIDS. While frequently fatal in its course, the life expectancy of those with KS is somewhat better than other opportunistic infections.