Kaposi's sarcoma

Kaposi's sarcoma is a rare type of cancer that can affect both the skin and internal organs.

The most common initial symptom of Kaposi's sarcoma is the appearance of red or purple patches on the skin. The patches then grow into lumps known as nodules.

Kaposi's sarcoma can also damage the internal organs, which can lead to a range of symptoms, depending on which organs are affected. These can include:

• breathlessness
• bleeding gums
• stomach pain
• leg swelling

Read more about the symptoms of Kaposi's sarcoma and diagnosing Kaposi's sarcoma.

Causes

Unlike most types of cancer, the cause for Kaposi's sarcoma has been identified. The condition is caused by a virus known as the human herpesvirus type 8 (HHV-8), also called the Kaposi's sarcoma-associated herpesvirus (KSHV).

HHV-8 is a relatively common virus. As many as 1 in 20 people may have the virus in their body, and in most cases it doesn't cause any noticeable symptoms. The majority of people with the virus don't develop Kaposi's sarcoma.

However, certain groups of people who are vulnerable to the effects of HHV-8 go on to develop Kaposi's sarcoma. These are usually people whose immune system isn't working properly, either because of another medical condition or medication that suppresses the immune system. 

A weakened immune system allows the HHV-8 virus to multiply to high levels in the blood, which increases the chance that it will cause Kaposi's sarcoma.

Read more about the causes of Kaposi's sarcoma.

Types of Kaposi's sarcoma

There are four main types of Kaposi's sarcoma, which are outlined below.

HIV-related Kaposi's sarcoma

Kaposi's sarcoma often affects people whose immune systems have been severely weakened by HIV. This used to be a common condition in people with HIV, although advances in medical treatment mean it is much less widespread nowadays. It is thought that HIV causes HHV-8 to multiply, increasing the chance it will cause Kaposi's sarcoma.

Kaposi's sarcoma is sometimes referred to as an "AIDS-defining" condition. This means that this cancer occurs when HIV has damaged the immune system so much that it cannot protect a person from certain infections and cancers. This advanced stage of HIV infection is sometimes known as acquired immune deficiency syndrome, or AIDS.

Endemic African Kaposi's sarcoma

Endemic African Kaposi's sarcoma is common in parts of Africa and is one of the most widespread types of cancer in that region, accounting for 1 in every 10 cases of cancer in Africa.

Although this type of Kaposi's sarcoma is classified separately from HIV-related Kaposi's sarcoma, it's highly likely that many cases are actually due to an undiagnosed HIV infection. In cases not related to HIV, it's thought this type of Kaposi's sarcoma develops due to a pre-existing genetic vulnerability to the HHV-8 virus.

Classic Kaposi's sarcoma

Classic Kaposi's sarcoma is a rare condition that mainly affects middle-aged and elderly men of Mediterranean or Ashkenazi Jewish descent. Ashkenazi Jews are people who are descended from Jewish communities that lived in central and eastern Europe. Most Jewish people in the UK are Ashkenazi Jews.

It is thought people who develop classic Kaposi's sarcoma were born with a pre-existing genetic vulnerability to the HHV-8 virus.

Transplant-related Kaposi's sarcoma

Transplant-related Kaposi's sarcoma is a rare complication of an organ transplant. It occurs because medication to weaken the immune system (immunosuppressants) is used after a transplant to help prevent the body rejecting the new organ. However, this also makes the person more vulnerable to the HHV-8 virus.

Treating Kaposi's sarcoma

The treatment for Kaposi's sarcoma largely depends on which form of the condition you have. If it is only spreading slowly, treatment may not be immediately necessary.

If the condition spreads more rapidly and is causing severe symptoms, a number of treatments may be used. These can include surgery to remove small tumours and chemotherapy or radiotherapy to kill the cancer cells.

With proper treatment, Kaposi's sarcoma can usually be controlled, and deaths from the condition in the UK are rare. However, it's important to understand a complete cure for all types of Kaposi's sarcoma isn't always possible, and there's a chance the condition could recur in the future.

Read more about treating Kaposi's sarcoma.