KS is divided into four types depending partly on ethnicity and geography, as follows:
This rare disease tends to occur in men of Mediterranean or Jewish heritage who are 50 years or older. Skin lesions usually appear on the feet or upper legs. This form of KS is generally benign.
This occurs in Africa and affects men and women across a broad range of ages, from young children to elderly people. This form of KS can affect the lymphatic system and internal organs, and as a result can be lethal.
People who have received organ transplants need to have their immune system suppressed so it does not attack or reject the new organ. In such cases where the immune system is deliberately weakened, KS can occur.
This form of KS affects mostly men, and, in rare cases, women who have sex with bisexual HIV positive men. KS is uncommon in people who inject street drugs. KS lesions may first appear anywhere on the skin and later grow near internal organs and lymph nodes.
Worldwide, HHV-8 infection is more common than KS. As a result, researchers suspect that there are co-factors that play a role in the development of this form of cancer.
HHV-8 is relatively common in parts of Central and East Africa, and researchers estimate that about 15% of people in North America are infected with this virus. It is likely that in North America and Western Europe gay and bisexual men have higher rates of infection -- perhaps about 25% are infected. Among MSM, the virus is probably spread by contact with saliva during sex. HHV-8 is less commonly found in other bodily fluids (such as semen).
In children, infection with HHV-8 can cause a red, itchy rash associated with fever. This virus is probably spread by contact with saliva from an infected adult.
HHV-8 infection seems to turn cells in the skin, blood and lymph vessels into KS tumours.
Tests for HHV-8 are available but researchers are not certain how to interpret the results. For instance, some of these tests can detect antibodies to HHV-8 and others can detect proteins of HHV-8. But exactly what these tests mean is unclear. So, for now, testing for HHV-8 is usually a research tool.