What is Kaposi sarcoma?
Kaposi sarcoma (KS) is a type of cancer of the lymphatic vessels and blood vessels which is seen mostly on the skin. Less commonly it may also occur in other tissue like that of the mouth, other parts of the gut and even the lungs. Kaposi sarcoma is a rare cancer but has become more common in recent decades mainly due to its association with HIV/AIDS. It is considered an AIDS-defining illness. This does not mean that Kaposi sarcoma will not occur in a person who is HIV negative. It is caused by a certain type of herpes virus and can affect any person although some people are at greater risk.
What causes Kaposi sarcoma?
Kaposi sarcoma has been associated with the human herpesvirus 8 (HHV-8). This virus is therefore also known as Kaposi sarcoma herpesvirus (KSHV). The virus then infects cells lining the lymphatic vessels and blood vessels. It causes these cells to become cancerous possibly by inserting its genes into the cell which then disrupts normal cell proliferation. The cells then divide rapidly in an uncontrolled manner as is the case with cancer. Although HHV-8 is easily transmitted through saliva, it will have major effects in most people who are HIV negative or with a healthy immune system.
It is once the immune defenses are compromised that HHV-8 can then lead to cancer. Therefore infection with HHV-8 in a person with a healthy immune system can go unnoticed. HHV is spread more often through contact with saliva than any other body fluid. It can therefore be transmitted between mother and child and even among close contacts and partners who are not sexually active. The disease is more aggressive in people infected with HIV illustrating that HIV co-infection somehow contributes to the effects of the virus.
Who gets Kaposi sarcoma?
Although Kaposi sarcoma is considered as one of the hallmarks of AIDS, it can affect any person irrespective of HIV status. It is more commonly seen in certain regions and ethnic groups when HIV infection or any other cause of a depressed immune system is not a factor. Kaposi sarcoma is associated with a HHV-8 and any person can be infected. However, not every person who is infected with this virus will develop Kaposi sarcoma. It is often easier to understand Kaposi sarcoma in relation the the different types.
- HIV infection, particularly advanced infection (low CD4 count).
- Living in sub-Saharan Africa.
- People of Mediterranean, Middle Eastern and Eastern European origin.
- Organ transplantation patients.
- Chronic or excessive use of corticosteroids and other immune suppressing drugs.
What are the types of Kaposi sarcoma?
Kaposi sarcoma can be broadly categorized into four types depending on who gets the disease.
- Epidemic Kaposi sarcoma (AIDS-related)
- Classic Kaposi sarcoma (Mediterranean)
- Endemic Kaposi sarcoma (African)
- Immunocompromised Kaposi sarcoma
Epidemic AIDS-related Kaposi sarcoma is seen in HIV infected patients and is a sign of AIDS, where the infection has progressed to the point that a large degree of the immune system has been compromised. It is the most common of the cancers in HIV. Although Kaposi sarcoma is so closely related to HIV infection, it does not occur in every AIDS patient. However, when it does arise it is considered as a sign that a person now has AIDS hence the term AIDS-defining illness. The availability of HAART (highly active antiretroviral therapy) has reduced the incidence of Kaposi sarcoma in people living with HIV/AIDS but does not offer complete protection. AIDS-related Kaposi sarcoma is usually more aggressive than other types.
Classic Mediterranean Kaposi sarcoma is seen mainly in elderly Mediterranean, Middle Eastern and Eastern European men. It can also occur in women from these regions but is far more common in men. It is believed that there may be several factors that contribute to Kaposi sarcoma in these cases apart from just genetics. Human herpesvirus 8 (HHV-8) infection is more common in these areas and it is therefore more likely to affect a person with a weakened immune system. This may be seen with an age-related decrease in immunity and other contributing factors to a depressed immune system like other cancers or concurrent infections (apart from HIV).
Endemic African Kaposi sarcoma is seen mainly in young adults and children in sub-Saharan Africa. However, the appearance of HIV and its prevalence in this region has led to AIDS-related Kaposi sarcoma shadowing endemic Kaposi sarcoma. Although human herpesvirus 8 (HHV-8) is more common in this part of Africa, there appears to be other factors that may have been responsible for endemic Kaposi sarcoma. It has been noted that not wearing shoes seems to increase the chances of endemic KS possibly due to some lymphatic disorder connected to direct contact with soil.
Immunocompromised Kaposi sarcoma occurs in a person with a severely suppressed immune system. This is more likely in a person who has had an organ transplant and using anti-rejection medication which suppresses the immune system hence the term transplant-associated Kaposi sarcoma. Since the use of immune suppressive medication even for other causes apart from a transplant can also lead to KS, this type is also known as iatrogenic Kaposi sarcoma.
How common is Kaposi sarcoma?
Kaposi sarcoma was a rare form of cancer in the United States prior to the emergence of HIV/AIDS. It was much more frequently seen in the Middle East, Mediterranean, Eastern Europe and Africa back then. However, HIV-infection has changed the epidemiology. Kaposi sarcoma is common in people living with HIV, particularly those cases which are not properly managed where HAART is not started once the CD4 count has dropped low. Proper immune monitoring and antiretrovirals has reduced the prevalence of Kaposi sarcoma even among HIV/AIDS patients. Nevertheless Kaposi sarcoma is about 200,000 more likely to occur in a person with HIV/AIDS that an HIV negative person (HIV seronegative).
What are the symptoms of Kaposi sarcoma?
The signs and symptoms of Kaposi sarcoma depends on the affected site.
- Most commonly affected site.
- Brown to red or purple nodules or blotches on the skin.
- Lesions are small and slightly raised (papular).
- Sometimes painful but not itchy rash.
- Rash worse on the head, neck and lower limbs.
Read more on other types of HIV skin rashes.
- Sometimes the first site that is affected.
- More likely to affect the gums and palate.
- Raised brown to dark lesions.
- Rash bleeds easily with chewing and brushing.
- Ulcerations of lesions and very large lesions can affect chewing and speaking.
Kaposi less often affects other sites like the nose, airways and lungs, and gastrointestinal tract (gut). Since it is not easily visible at these other sites it may often be missed. The symptoms of Kaposi sarcoma at sites other than the skin and mouth may instead be associated with other opportunistic infections.
|Pictures of Kaposi sarcoma sourced from Wikimedia Commons and Dermatology Atlas Brazil courtesy of Samuel Freire da Silva, M.D.|
How is Kaposi sarcoma diagnosed?
Physical examination of the lesions on the skin and in the mouth may be sufficient to reach a diagnosis. It should, however, be confirmed by checking the CD4 count and doing a biopsy. Investigations for other sites includes :
- Chest X-ray
- Endoscopy of the gastrointestinal tract with biopsy.
- Bronchoscopy for the respiratory tract but biopsy should be avoided due to extensive bleeding.
Kaposi sarcoma is not often misdiagnosed as health care professionals have become more familiar with the condition in recent years due to AIDS. The characteristic appearance of lesions on the skin and in the mouth in a person who is HIV positive is usually sufficient to make the diagnosis. Biopsy only serves to confirm the diagnosis. A condition known as bacillary angiomatosis may also present with skin lesions similar to Kaposi sarcoma. This infection is also commonly seen with HIV infection.
What is the treatment for Kaposi sarcoma?
Highly active antiretroviral therapy (HAART) should be commenced immediately in patients living with HIV once Kaposi sarcoma is diagnosed. Other treatment options depends on the individual case. It may include :
- Radiation therapy which helps ease the symptoms and cosmetic aspect of the disease.
- Surgical removal of small lesions on the skin surface or deeper lesions.
- Freezing (cryotherapy) of the skin lesions particularly on the face.
- Laser therapy (photocoagulation) to shrink skin lesions and ease pain and bleeding of deeper lesions.
- Topical applications such as retinoids to slow tumor growth.
- Injectable solutions (chemotherapy and biological therapy) such as anthracyclines, interferons, taxanes and vinca alkaloids.