Kaposi sarcoma (KS) is the most common cancer seen in HIV. This cancer is caused by the human herpes virus 8 (HHV-8), also known as Kaposi sarcoma-associated herpesvirus (KSHV). The virus can be spread by deep kissing, unprotected sex, and sharing needles. It also can be spread from mother to child. However, HIV-related KS usually develops only in people with relatively advanced HIV disease.

Symptoms include brown, purple, or pink lesions (or blotches) on the skin, usually on the arms and legs, neck or head, and sometimes in the mouth. KS can also affect the lungs and intestines and cause swelling in the legs. Sometimes there is tooth pain or tooth loss, weight loss, night sweats, or fever for longer than 2 weeks.

HIV drugs can slow the growth of lesions, and even reverse the condition itself. KS has become less common and much more treatable since the development of effective HIV therapy. Other treatments for KS, such as laser therapy, are meant to relieve symptoms and improve the appearance of the lesions. There is also chemotherapy that helps control KS.