Kaposi’s Sarcoma and the Virus/Cancer Connection (Part 1)

Is cancer a contagious disease? The simple answer to that question is “No.” At least, that’s what we tell people. You can’t catch cancer from someone who has it. If a cancer patient is isolated, it’s to protect the patient from us, not the other way around. But, as is often the case, the truth is not quite so simple.

Let’s take a trip back in time. It’s 1984. Arguments rage about what to call the newly discovered virus that seems to cause this new disease called Acquired Immune Deficiency Syndrome (the American group proposed calling the virus HTLV-III while their French competitors wanted to call it LAV). When the dust settles, the virus is called HIV, and it quickly becomes clear that infection with HIV is not the same thing as having AIDS. So how do we define AIDS? Well, a person has AIDS if s/he is infected with HIV and has one of the so-called “AIDS Defining Illnesses.” Interestingly, one of these is a kind of cancer called Kaposi’s Sarcoma. Kaposi's Sarcoma causes nodules or blotches that may be red, purple, brown, or black. They are typically found on the skin, but spread elsewhere is common, especially the mouth, gastrointestinal tract and respiratory tract. Growth can range from very slow to explosively fast, and may be fatal.



All of the other AIDS defining illnesses, however, are infections that usually strike people with weakened immune systems (like cancer patients). So what is Kaposi’s Sarcoma doing on the list?

That question remained a mystery for quite a while. After all, although Kaposi’s Sarcoma was first described in 1872, it was originally known as a disease that affected older men from the Mediterranean region or who were of Ashkenazi Jewish descent. Yet, these men didn’t have AIDS, and no one knew why Kaposi’s sarcoma seemed to disproportionately affect this population. There is also a form of Kaposi’s Sarcoma endemic to sub-Saharan Africa, and although HIV infection is prevalent there now, that was not the case when endemic Kaposi’s Sarcoma was first described.

An answer to this mystery became apparent in 1994 when a group at Columbia University showed that Kaposi’s Sarcoma is actually caused by a virus. Originally they called it Kaposi’s Sarcoma Herpes Virus (because it is closely related to the viruses that cause herpes), but is has since been renamed HHV-8 (human herpesvirus 8). Subsequent work has shown that all forms of Kaposi’s Sarcoma are associated with an HHV-8 infection.

Over the years since the beginning of the AIDS epidemic, we have gotten pretty good at treating HIV infection, and with HAART (highly active anti-retroviral therapy), HIV infection has morphed from a rapidly fatal infection to a chronic disease. A by-product of the advent of HAART was the apparent disappearance of Kaposi’s Sarcoma. What was once an AIDS-defining illness, affecting as many as 80% of AIDS patients, there have been very few cases in the past 10 years.

Until now.

15 Kaposi’s Sarcoma cases were recently identified by doctors at San Francisco General Hospital. Surprisingly, these cases occurred in patients whose HIV infections were well controlled on HAART. This has prompted speculation about what happens as the immune system ages. These men all have undetectable HIV levels and normal numbers of white blood cells. Of course, so do the Ashkenazi Jewish men who used to be the primary group of KS patients. So what does this mean? Right now, no one is certain. But like all medical mysteries, we will all be a lot smarter once we figure it out.