Causes and Risk Factors of Kaposi's Sarcoma

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Kaposi's sarcoma (KS) is a type of cancer caused by an infection with a virus called human herpesvirus 8 (HHV-8), which is also known as Kaposi's sarcoma–associated herpesvirus (KSHV). The virus, which is in the same family as the Epstein-Barr virus, is rare in the United States. In fact, less than 1% of the general U.S. population is a carrier of the virus.

Being a carrier of KSHV alone does not lead to a cancer diagnosis. Most people who develop KS have KSHV and also have a weakened immune system, due to human immunodeficiency virus (HIV) infection, organ transplantation, being older, or some other factor.

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Types of Kaposi's Sarcoma

There are four types of KS, which is a cancer that develops in the lining of blood and lymph vessels and forms tumors, or skin lesions. The four types are:

  • Epidemic (AIDS-associated) Kaposi's sarcoma: The most common type of KS in the United States develops in people who have HIV (the virus that causes AIDS).
  • Classic Kaposi's sarcoma: Classic Kaposi's sarcoma is rare. It is more common in older men of Mediterranean, East Asian, or Jewish descent.
  • Iatrogenic (transplant-related) Kaposi's sarcoma: This type of KS develops in people who have had an organ transplant.
  • Endemic Kaposi's sarcoma: Endemic Kaposi's sarcoma is most common in sub-Saharan Africa, where HHV-8 is more common. It usually develops in younger people (under the age of 40).

Common Causes

Anyone can get KS. But there are some factors that can increase your risk. Knowing your risk factors and talking about them with your doctor may help you make better-informed healthcare choices.

In the United States, studies have found that less than 10% of people are infected with KSHV. U.S. infections are more common in people infected with HIV than in the general population. KSHV infection is also more common in men who have sex with men (MSM) than in men who only have sex with women.

The following factors can raise a person’s risk of developing Kaposi's sarcoma:

  • Infection with human herpesvirus 8: This virus, also called the Kaposi's sarcoma herpesvirus (KSHV), causes KS. However, most people with KSHV infection do not develop Kaposi's sarcoma. The cancer appears most often when a person with KSHV also has problems with their immune system function.
  • Ethnicity: People of Jewish or Mediterranean descent, as well as those living in sub-Saharan Africa, have a higher risk of developing Kaposi's sarcoma. Currently, KS is one of the most common cancers in certain sub-Saharan African countries, where 89% of all KS cases occur.
  • Gender: Men have a higher risk of developing Kaposi's sarcoma than women.
  • Immune deficiency: People with HIV/AIDS and people whose immune systems are suppressed after organ transplantation have a higher risk of developing Kaposi's sarcoma. KS incidence is one in 100,000 in the general population, but in HIV-infected individuals, it is around one in 20. About one in 200 transplant patients in the United States gets KS.

Preventing Kaposi's Sarcoma Herpesvirus

There are no vaccines at this time to protect people against KSHV. For now, preventing KS depends on reducing the chance of becoming infected with KSHV and reducing the chance that people who are infected with KSHV will go on to develop KS.

Genetics

KS is not usually hereditary, although there are some reports of classic KS running in families. To date, approximately 100 cases of KS within families have been reported.

Despite the lack of evidence to suggest that KS is hereditary, the most common method of transmission of KSHV, the virus that causes KS, is saliva, which means that it can be passed through families.

In some areas of Africa, up to 80% of the population shows signs of KSHV infection. In these areas, the virus seems to spread from mother to child.

HIV infection is not transmitted via saliva, but the most common method of transmission of KSHV, the virus that causes Kaposi's sarcoma, is saliva.

Lifestyle Risk Factors

As most cases of KS in the United States occur in people with HIV and AIDS, you can significantly lower your risk of developing KS by avoiding the known risk factors for acquiring HIV. This includes avoiding having unprotected sex and sharing intravenous (IV) needles.

The use of antiretroviral therapy (ART) decreases a person's risk of getting HIV after a sexual exposure by more than 99%. In addition, pre-exposure prophylaxis (PrEP) may lower the risk of HIV infection by more than 90% for certain groups of people.

If you are living with HIV or AIDS, adhering to your treatment protocol and keeping regular medical appointments is really important. In the United States, the rate of adherence to HIV therapy is generally low. A meta-analysis of adherence studies reported that just 55% of a pool of 17,573 patients stuck with their HIV treatment plan.

Adhering to medication and medical appointments is a key way to prevent your immune system from going into decline, which can put you at risk of developing Kaposi's sarcoma.

A Word From Verywell

Kaposi's sarcoma herpesvirus (KSHV) can cause Kaposi's sarcoma, but not everyone with the virus will get cancer.

The most at-risk population in the United States is people living with HIV and AIDS. Regular doctor's visits, adhering to medication protocols, and practicing safe sex may reduce your risk of becoming seriously ill with this rare cancer.

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