Final answer:
Prior to 1980, Kaposi's sarcoma was predominantly seen in elderly individuals, but this changed in the early 1980s with the emergence of AIDS, when it became associated with young men, particularly in the gay community, who had compromised immune systems.
Step-by-step explanation:
Prior to 1980, Kaposi's sarcoma was mainly seen in the elderly population as a relatively innocuous disease. This shift in demographic began to emerge in the early 1980s when young men, especially from the gay community in large cities such as San Francisco and New York, started to display symptoms of a more severe form of Kaposi's sarcoma, alongside other opportunistic infections like a rare form of pneumonia.
Initially, there was confusion about the disease, as it was termed Gay Related Immune Deficiency (GRID) due to its prevalence in the gay population. It was later identified that these young patients had compromised immune systems with severely reduced white blood cell counts, specifically CD4+ T cells. This pointed to Acquired Immune Deficiency Syndrome (AIDS), caused by the human immunodeficiency virus (HIV). Kaposi's sarcoma then became known as an opportunistic cancer associated with AIDS, affecting 10 to 20 percent of AIDS patients and characterized by purplish lesions on the skin.