Kaposi's Sarcoma and AIDS result from two different viruses, but
the development of Kaposi's Sarcoma can precede the progression of
HIV to AIDS. The HIV virus attacks a person's immune system, and a
weakened immune system makes it likely that a person already
infected with the Kaposi virus will develop Kaposi's Sarcoma. The
type of severe weakening of the immune system that allows the
development of Kaposi's Sarcoma is also what causes HIV to develop
into AIDS.