Kaposi's sarcoma natural history

Overview
With the decrease in the death rate among AIDS patients receiving new treatments in the 1990s, the incidence and severity of epidemic KS also decreased. However, the number of patients living with AIDS is increasing substantially in the United States, and it is possible that the number of patients with AIDS-associated Kaposi's sarcoma will again rise as these patients live longer with HIV infection.

Natural history
The disease is named after Moritz Kaposi (1837–1902), a Hungarian dermatologist who first described the symptoms in 1872. Research over the next century suggested that KS, like some other forms of cancer, might be caused by a virus or genetic factors, but no definite cause was found.

With the rise of the AIDS epidemic, KS, as initially one of the most common AIDS symptoms, was researched more intensively in hopes that it might reveal the cause of AIDS.

In 1994, Yuan Chang, Patrick S. Moore, and Ethel Cesarman at Columbia University in New York isolated genetic pieces of a virus from a KS lesion. They used representational difference analysis (a method to subtract out all of the human DNA from a sample) to isolate the viral genes. They then used these small DNA fragments as starting points to sequence the rest of the viral genome in 1996. This, the eighth human herpesvirus (HHV-8)&#151;now known as Kaposi's sarcoma-associated herpesvirus (KSHV)&#151;has since been found in all KS lesions tested, and is considered the cause of the disease. KSHV is a unique human tumor virus that has incorporated cellular genes that cause tumors into its genome ("molecular piracy"); the stolen cellular genes may help the virus escape from the immune system, but in doing so it also causes cells to proliferate. It is related to Epstein-Barr virus, a very common herpesvirus that can also cause human cancers.

KSHV infection does not always lead to KS; it is still unclear what other factors may be required, such as pre-existing immune system damage, or a specific interaction with HIV or other viruses. However, research in Africa has shown that even in the absence of HIV/AIDS, KS is more common in men than women although KSHV infection is equal between both sexes. This suggests that sex hormones may either protect from or predispose to KS in persons infected with the virus.