In the early stages of the AIDS epidemic, Kaposi sarcoma suddenly became a more common disease than it had ever been in the past. In fact, the sudden appearance of an unusually large number of cases of Kaposi sarcoma was one of the first things that alerted doctors to the fact that a new disease - eventually named AIDS - had emerged.
Kaposi sarcoma was particularly common among AIDS patients who were homosexual men, many of whom had been exposed to the virus that causes Kaposi sarcoma through sexual activity and then developed the cancer after the AIDS virus suppressed their immune systems. Prior to the development of effective treatments for HIV infection, about one-fourth of male homosexual AIDS patients developed Kaposi sarcoma. The frequency of the cancer was lower in other groups of AIDS patients, presumably because they were less likely to have been exposed to the virus through sexual activity. However, some cases have occurred among women and heterosexual men with AIDS.
After drugs to treat HIV infection were developed, the rate of Kaposi sarcoma among HIV-infected people dropped sharply. The drugs help keep the immune system functioning, and that reduces the chance of developing Kaposi sarcoma. Another factor that has led to a decrease in the number of cases of Kaposi sarcoma is increased awareness of how HIV is transmitted and how transmission of the disease can be prevented. Because of a combination of fewer new cases of HIV infection and more effective drugs to treat HIV infection, the rate of Kaposi sarcoma has dropped by about 85 to 90% since the high levels seen in the early 1990s.
The AIDS-related form of Kaposi sarcoma typically causes widespread abnormal patches that develop in many places on the body. This is different from the pattern in classic Kaposi sarcoma, where most patients develop patches on only one or a few areas of their skin, usually on the lower legs. Prior to the development of drugs to treat AIDS, the cancer would usually spread throughout the body, and AIDS patients would sometimes die of Kaposi sarcoma that had spread to their lungs. Today, however, this rarely happens because treatment of the HIV infection usually prevents Kaposi sarcoma from progressing to such an advanced stage.