Kaposi's sarcoma is a rare type of cancer caused by a virus. It can affect the skin and internal organs.
It's mainly seen in people with a poorly controlled or severe HIV infection. It can also affect some people who have a weakened immune system for another reason, as well as people who have a genetic vulnerability to the virus.
See What causes Kaposi's sarcoma? for more information.
Signs and symptoms
The most common initial symptom is the appearance of small, painless, flat and discoloured patches on the skin or inside the mouth. They're usually red or purple and look similar to bruises.
Over time, the patches may grow into lumps known as nodules and may merge into each other.
Internal organs can also be affected, including the lymph nodes, lungs and the digestive system, which can cause symptoms such as:
The rate at which symptoms progress depends on the type of Kaposi's sarcoma you have. Most types get worse quickly in a matter of weeks or months without treatment, but some progress very slowly over many years.
When to seek medical advice
You should see your GP if you have any worrying symptoms you think could be caused by Kaposi's sarcoma. If you have HIV, you can also contact your local HIV clinic if you have any concerns.
Your doctor will ask about your symptoms and examine your skin to look for the characteristic discoloured patches. If they suspect Kaposi's sarcoma, they will refer you for further tests to confirm the diagnosis.
These tests may include:
- an HIV test – a blood test to confirm whether or not you have HIV (if you haven't already been diagnosed with the condition)
- a skin biopsy – where a small sample of cells is removed from an affected area of skin and checked for Kaposi's sarcoma cells
- an endoscopy – where a thin, flexible tube called an endoscope is passed down your throat to see if your lungs or digestive system are affected
- a computerised tomography (CT) scan to see if your lymph nodes or other parts of your body are affected
What causes Kaposi's sarcoma?
Kaposi's sarcoma is caused by a virus called the human herpesvirus 8 (HHV-8), also known as the Kaposi's sarcoma-associated herpesvirus (KSHV). This virus is thought to be spread during sex, through saliva, or from a mother to her baby during birth.
HHV-8 is a relatively common virus and the vast majority of people who have it will not develop Kaposi's sarcoma. It only seems to cause cancer in some people with a weakened immune system and in some people who have a genetic vulnerability to the virus.
A weakened immune system allows the HHV-8 virus to multiply to high levels in the blood, which increases the chance it will cause Kaposi's sarcoma.
The virus appears to alter the genetic instructions that control cell growth. This means some cells reproduce uncontrollably and form lumps of tissue known as tumours.
Types of Kaposi's sarcoma and their treatment
There are four main types of Kaposi's sarcoma. These types affect different groups of people and are treated in different ways.
HIV-related Kaposi's sarcoma
Although it's not as common as it used to be, Kaposi's sarcoma is still one of the main types of cancer to affect people with HIV.
HIV-related Kaposi's sarcoma can progress very quickly if not treated. However, it can usually be controlled by taking HIV medication – known as combination antiretroviral therapy (cART) – to prevent HIV multiplying and allow the immune system to recover. The immune system can then reduce the levels of HHV-8 in the body.
Read more about treating HIV.
Some people may also require treatment with radiotherapy (where high-energy rays are used to destroy cancer cells) or chemotherapy (where powerful medications are used to destroy cancer cells), depending on the site and extent of the cancer and what symptoms it's causing.
Classic Kaposi's sarcoma
Classic Kaposi's sarcoma mainly affects middle-aged and elderly men of Mediterranean or Ashkenazi Jewish descent. Ashkenazi Jews are descended from Jewish communities that lived in central and eastern Europe. Most Jewish people in the UK are Ashkenazi Jews.
It's thought people who develop classic Kaposi's sarcoma were born with a genetic vulnerability to the HHV-8 virus.
Unlike the other types of Kaposi's sarcoma, the symptoms of classic Kaposi's sarcoma progress very slowly over many years and are usually limited to the skin.
Immediate treatment isn't usually required because, in many cases, the condition doesn't affect life expectancy. You'll usually be monitored carefully and only treated if the symptoms get significantly worse.
Radiotherapy is often used if treatment is required, although small skin patches or nodules may be removed using minor surgery or cryotherapy (freezing).
Transplant-related Kaposi's sarcoma
Transplant-related Kaposi's sarcoma is a rare complication of an organ transplant. It occurs because the immunosuppressant medication used to weaken the immune system and help prevent the body rejecting the new organ can allow a previous HHV-8 infection to reactivate, which means levels of the virus increase as it starts multiplying again.
Transplant-related Kaposi's sarcoma can be aggressive and usually needs to be treated quickly. It's normally treated by reducing or stopping the immunosuppressants, if this is possible. If this is unsuccessful, radiotherapy or chemotherapy may be used.
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.
Although this type of Kaposi's sarcoma is classified separately from HIV-related Kaposi's sarcoma, many cases may actually result from an undiagnosed HIV infection. All suspected cases therefore must have an HIV test, as the most effective treatment in these cases is HIV medication.
In cases not caused by HIV infection, this type of Kaposi's sarcoma may be the result of a genetic vulnerability to HHV-8. These cases are usually treated with chemotherapy, although sometimes radiotherapy may be used.
With proper treatment, Kaposi's sarcoma can usually be controlled for many years. Deaths from the condition are uncommon in the UK.
The discoloured patches of skin will often shrink and fade with treatment, although they may not ever disappear completely.
A complete cure for any type of Kaposi's sarcoma isn't always possible, and there's a chance the condition could recur in the future. If you think this is happening, contact your HIV clinic, hospital specialist or GP as soon as possible.