Kaposi Sarcoma Causes, Risk Factors, and Prevention

Kaposi sarcoma (KS) is caused by infection with a virus called the Kaposi sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus 8 (HHV-8).

Most people infected with this virus never develop KS, but several known risk factors increase the chance of this happening. If you are at higher risk, there may be ways to lower your risk.

What are the risk factors for Kaposi sarcoma?

A risk factor is anything that increases your chance of getting a disease such as cancer. Some risk factors might cause cancer, while others are just linked to a higher risk in some way. Different cancers have different risk factors.

There are some known risk factors for Kaposi sarcoma (KS). To some extent, these risk factors depend on the type of KS, but they include:

• Infection with Kaposi sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus 8 (HHV-8): This is the main cause of KS, although most people infected with this virus never develop KS. It is described in more detail below.
• Infection with HIV, the virus that causes AIDS
• Taking immune-suppressing medicines after an organ transplant
• Being male: Men are more likely than women to get all types of KS. The reasons for this aren’t fully understood.
• Sexual activity: Men who have sex with men are at higher risk of getting KS, regardless of their HIV status.
• Living in certain parts of the world: KS is much more common in Sub-Saharan Africa, where much more of the population has been exposed to KSHV.

What causes Kaposi sarcoma?

Kaposi sarcoma is caused by infection with a virus called the Kaposi sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus 8 (HHV-8).

KSHV infects cells that line blood and lymph vessels (endothelial cells). It brings in genes that make the cells divide too much, live longer than they should, and sometimes form new blood vessels or release chemicals that cause inflammation. Over time, these changes can turn the cells into cancer.

Most people infected with KSHV never develop Kaposi sarcoma. It is much more likely to develop when a person with KSHV also has a weakened immune system, such as from HIV infection, medicines taken after an organ transplant, or older age.

How does the virus spread?

KSHV seems to spread mainly through saliva, although it’s possible the virus can spread in other ways as well.

The number of people infected with KSHV varies around the world. For example:

• In the United States, most of Europe, and Asia, fewer than 1 in 10 people are infected with KSHV. It is more common in some groups of people, such as those with HIV and men who have sex with men.
• In some areas of Africa, up to 8 in 10 people have KSHV, and the virus often passes from mother to child.

For more on infections and their role in cancer, see Infections That Can Lead to Cancer.

Can Kaposi sarcoma be prevented?

Kaposi sarcoma is caused by the Kaposi sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus 8 (HHV-8). At this time, there are no vaccines to protect people from KSHV infection.

The main way to prevent Kaposi sarcoma is to reduce the chances that a person infected with KSHV will develop this cancer. People at highest risk include those with HIV and AIDS and those who are taking medicines to suppress their immune system after an organ transplant.

Lowering your risk of getting HIV

Most cases of Kaposi sarcoma in the United States happen in people with HIV. Taking measures to avoid HIV infection could help prevent many cases of KS in the US.

For example:

• Using safer sex practices
• Using clean, sterile needles and supplies if you use injection drugs
• Taking pre-exposure prophylaxis (PrEP) if you are at high risk of HIV
• Reducing transmission of HIV from mothers to their babies

For more on lowering your risk of getting HIV, see What Are HIV and AIDS?

Lowering your risk if you have HIV

If you are infected with both HIV and KSHV, taking the right medicines can lower your chance of developing Kaposi sarcoma.

If you have HIV, treatment with antiretroviral therapy (ART) helps keep your immune system strong. Along with lowering your risk of AIDS, ART reduces the risk that you will develop Kaposi sarcoma, although it doesn’t eliminate it completely.

People with HIV who take medicines to treat herpesvirus infections, such as ganciclovir or foscarnet, may be less likely to develop Kaposi sarcoma. This is because these drugs also work against KSHV, which is a type of herpesvirus. But the drugs can have serious side effects, so they are only used to treat certain viral infections, not to help prevent Kaposi sarcoma.

Lowering your risk if you have an organ transplant

If you are at risk of developing iatrogenic Kaposi sarcoma after an organ transplant, your risk might be reduced if you use immune-suppressing drugs known as mTOR inhibitors, such as sirolimus or everolimus, instead of other immune-suppressing drugs.

Of course, this must be balanced against making sure your body doesn’t reject the new organ.