What Causes It The cause of classic, old-fashioned KS is unclear. KS as it originally occurred in Africa likewise has no clearly defined cause. Epidemic KS, occurring as a disease that defines AIDS, is thought to have a cause—the virus named HIV (human immunodeficiency virus). If given a blood test for HIV, nearly all patients with epidemic KS will show evidence of being infected.
Various ideas have been put forward to explain how the virus causes this illness. One theory is that the virus, either directly or by initiating a chain of events, causes a normal cell to become malignant . Various agents that may be involved in such a change have been identified. Yet another idea has to do with the body's T cells . Some of these cells hunt for malignant cells that develop spontaneously and kill them off before they can become established as cancers. Under this theory, the T cell is infected with the HIV virus and cannot kill the malignant cells.
With AIDS-related KS, there is also the continuing issue of whether HIV alone is responsible for the disease. Other factors have been suggested as co-producers of the illness, including drugs and other viruses. The agent most often mentioned is CMV (cytomegalovirus), but this is by no means the only one. It may also be that CMV and other agents produce substances that stimulate the growth of KS through interleukin-6 or other factors.
KS in people who have taken drugs to depress the body's immune response is thought to occur in a fashion similar to that in patients with epidemic KS.
