Introduction

Kaposi sarcoma is a rare type of cancer that often presents as skin lesions.¹ It occurs in patients who have a suppressed immune system, such as those with human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDs), and those who have undergone a transplant.¹ It is caused by a virus, human herpesvirus 8 (HHV8), and has a varied global distribution with a higher incidence in sub-Saharan Africa and in those of Mediterranean descent.¹

What is Kaposi sarcoma? 

Kaposi’s sarcoma is an uncommon form of cancer originating from endothelial cells, which are a type of soft tissue found in the lining of blood vessels and lymphatic system that plays a vital role in important internal processes of the body, such as regulating blood flow, controlling bleeding and effective functioning of the immune system.^1,2 

Signs and symptoms of Kaposi sarcoma

• Lesions on the skin of red or purple colour that may develop into a patch,plaque, and eventually into a lumpy ulcerating nodule¹
• Lesions in inner mucosal surfaces like the lining of the mouth, throat and nose¹
• Swelling of the lymph nodes
• Breathlessness or nausea as Kaposi sarcoma may affect organs, more commonly the lungs and the gastrointestinal system¹

If you suspect an abnormality in your skin, swelling or discomfort in areas surrounding your organs, it is important to seek healthcare advice to receive an accurate diagnosis and an appropriate treatment plan.

What is the cause of Kaposi sarcoma? 

Kaposi sarcoma is caused by HHV8, which is transmitted through bodily fluids such as saliva , blood, and through sexual contact.¹ HHV8 infects endothelial cells and causes abnormal changes in cell regulation and blood vessel formation.¹ The virus-infected cells undergo accelerated growth , which may go unchecked and result in the formation of lesions or tumours.¹ 

Sometimes the immune system is able to recognise and defend itself against cancer cells.⁵ But often cancer cells develop mechanisms that evade detection and removal by immune cells.⁵ Therefore, Kaposi sarcoma is most common in patients with a weakened immune system, particularly those with AIDs or those who are on medication to suppress the immune system after an organ transplant.^1, 

Not everyone who contract HHV8 will develop Kaposi sarcoma as they may have a strong enough immune system and the infection may not be obvious.⁶ There are other factors that may increase the likelihood of developing Kaposi sarcoma, such as genetic, environmental and individual characteristics.⁷ Additionally, Kaposi sarcoma is more commonly found in men than in women, and in areas of sub-Saharan Africa.^1,7 The geographic and demographic distribution of Kaposi sarcoma will be discussed in further in this article.

What are the different types of Kaposi sarcoma?

There are 4 different categories of Kaposi sarcoma.

1. Classic Kaposi sarcoma only affects the skin of the lower limbs, with a higher occurrence in middle-aged and older patients with ethnic origins of Eastern Europe, Middle East or the Mediterranean.¹,⁸ It is a less aggressive form of the disease but those with the classic form are at a higher risk of secondary cancer.¹,⁸
2. HIV-related Kaposi sarcoma, also known as the epidemic form, is the most common type found in patients. It presents as lesions on the skin and mucosal surfaces and affects internal organs as well. As patients infected with HIV have a weakened immune system, it increases their chance of developing Kaposi sarcoma.¹,⁸ 
3. Endemic Kaposi sarcoma describes the cancer that is commonly found in areas throughout Africa, with a higher proportion of children and adults below the age of 40 being affected. It has been observed that this type of Kaposi sarcoma can progress more aggressively and involve more areas of the body.¹,⁸
4. Transplant-related Kaposi sarcoma, also known as the iatrogenic form, may be found in patients who have had an organ transplant and require medication to dampen the immune system to be able to accept the new organ without rejection.¹,⁸

How is Kaposi sarcoma globally distributed? 

Africa

In 2020, 73% of all cases and 86% of Kaposi sarcoma deaths in the world are from Africa, which carries the largest disease burden, particularly in sub-Saharan Africa, where HHV8 positivity is found in 40-90% of the population compared to below 10% in other countries in Asia, northern Europe and North America.⁷ Also, 70% of HIV infections worldwide, which is strongly linked to kaposi sarcoma development, were found in sub-Saharan Africa.⁷ However, some studies have shown a reduction in cases in many areas of this region, including Kenya, Uganda and Zimbabwe.^10,11,12 This has been largely associated with increased availability and use of antiretroviral therapy for HIV treatment.^1,7 There has also been an association of HHV8 infection with malaria exposure, which can negatively affect the ability of the immune system to detect foreign entities and abnormal cells in the body, which increases the risk of sarcoma.^1,13

Mediterranean and Middle East

The Mediterranean population is the second largest group, following sub-Saharan countries, to have an HHV8 infection of around 20-30%.⁸ Classic Kaposi sarcoma is typically seen in men of Mediterranean origin.^1,7,8 Although there is a downward trend of Kaposi sarcoma incidences in this region, Turkey was observed to have an increase in new Kaposi sarcoma cases .⁷ 

Northern Europe, Asia and USA

There has been a general decrease of Kaposi sarcoma incidences across North America, northern Europe and Asia.⁷ However, the Netherlands has seen an increase in cases even though HIV incidences are lower than in other European countries.⁷ A similar trend is seen among black Americans, especially MSM, where incidences have increased.^7,14 This may be due to undetected and untreated HIV infections.⁷

Other demographic patterns

Age

The age range Kaposi sarcoma is seen varies across different types.¹⁵ Classic Kaposi sarcoma is usually diagnosed in adults over the age of 50 years. ^1,15 In patients with HIV, the impacted population is generally younger.^1,15 HHV8 seems to be transmitted at an earlier age in areas across Africa, through salivary contact, with a matched parallel in the occurrence of endemic Kaposi sarcoma.^1,16

Gender

Kaposi sarcoma is more likely to be found in men than women, across all types of the disease, with a ratio of 2:1 for endemic Kaposi sarcoma.^1,17 and 3:1 for transplant-related kaposi sarcoma.^1,18 Particularly men who have sex with men (MSM) are at a higher risk. .^1,18,19

Weakened immune system

HIV/AIDs is a key risk factor as HIV-related Kaposi sarcoma is the most common form of the disease globally, with homosexual men with HIV seeing a 5-10 times increased risk.^1,18, Some studies show Kaposi sarcoma is found in up to 30% of patients with untreated HIV.^1,18,20 In the UK94% of individuals with Kaposi sarcoma have both HHV8 and HIV infection.²¹

Similarly, patients who have had a transplant also have an increased risk of developing Kaposi sarcoma. Solid organ transplants increase this risk more than bone marrow or peripheral blood stem cell transplants.^1,18,22 More than a twentieth of patients who have undergone a transplant will develop Kaposi sarcoma.¹

Why is it important to understand the distribution of Kaposi sarcoma?

With better knowledge of the geographical distribution of Kaposi sarcoma and areas with the highest disease burden, public health and government resource allocation can be optimised to improve outcomes.⁷ One of the main challenges is the accessibility for HIV diagnosis and treatment.^1,7 Encouraging testing and improving care for high-risk groups can better prevent HIV transmission and the development of Kaposi sarcoma.⁷

Summary

Even though Kaposi sarcoma is rare, there are still noticeable trends in certain geographic and demographic distributions worldwide, particularly in certain regions of Africa and in men who have sex with men. In recent years, there has been a decrease in Kaposi sarcoma incidences likely due to the effectiveness of antiretroviral therapy targeting HIV. However, ongoing efforts are still needed in order for high-risk groups to receive timely diagnosis and treatment, and to prevent future transmission of HIV and development of Kaposi sarcoma. 

FAQs

1. How is Kaposi sarcoma diagnosed and evaluated?

A physical examination of the skin lesion(s) by a doctor is the first step in diagnosing the condition. However, for definitive diagnosis, a biopsy is needed, where a part of the lesion(s) is removed and examined under the microscope. There are other tests that might be performed such as blood tests to check for HIV and endoscopy, where a camera on top of a thin tube is passed through the mouth and throat to check lining of the stomach or lungs. Imaging studies such as chest x-rays or CT scans may also be performed to see if there are any internal involvement.

2. What are the currently available treatment options for Kaposi sarcoma?

Healthcare professionals from different specialities can together create a personalised treatment plan for each individual, depending on the type of Kaposi sarcoma and the location and size of the lesions. Treatment options include special topical creams, surgery, and cryotherapy to remove the cancerous lesions. Targeted or intravenous chemotherapy or radiotherapy may also be used.