Kaposi Sarcoma

Basics

Kaposi sarcoma (KS) was originally described in 1872 by a Hungarian dermatologist named Moritz Kaposi.

Synonym(s): KS; multiple idiopathic hemangiosarcoma
KS is a low-grade vascular tumor associated with human herpesvirus 8 (HHV-8), a γ-herpesvirus.
Kaposi sarcoma–associated herpesvirus (KSHV), another name for HHV-8, is the etiologic agent of all clinical forms of KS and several other lymphoproliferative diseases, including primary effusion lymphoma (PEL) and multicentric Castleman disease (MCD).
Four major forms are seen:
- Epidemic/AIDS-associated KS: seen primarily in patients with lower CD4 counts, especially among patients who are not on highly active antiretroviral therapy (HAART)
- Iatrogenic/transplant-associated KS: seen in patients who are posttransplant and/or on immunosuppressive medication regimens
- Endemic/African KS: seen in equatorial Africa, especially sub-Saharan countries
- Classic/sporadic KS: rare, mostly seen in elderly men in the Mediterranean and Eastern European regions
Systems affected: hemolytic/lymphatic/immunologic; skin/exocrine; gastrointestinal; pulmonary
Fulminant lymphadenopathic disease is a subtype of endemic KS occurring in young children.

Predominant age: 16 to 70 years; African KS predominant age: 35 to 40 years; classic KS age: 50 to 70 years; AIDS-related KS age: 20 to 54 years
Predominant sex: in the United States, epidemic KS: male > female ~50:1; classic and endemic KS: male > female ~10:1

Incidence

~2,500 cases occur yearly in the United States, most often in people infected with HIV.
The U.S. incidence of KS after transplantation is estimated to be 1 in 200; renal transplant recipients are most frequently affected.
Incidence of KS has decreased greatly since the advent of HAART; KS in the United States peaked at 47 cases per million at the height of the AIDS epidemic and now occurs at rate of 6 cases per million people each year.

Prevalence

Before HAART, KS was >20,000 times more common in AIDS patients than in the general population.
The seroprevalence of KSHV in the United States is <1–5%, but among MSM, prevalence is 20–77%; in certain parts of Africa, rates can reach >80%.
AIDS-related KS may occur at normal CD4 cell counts but is more common at CD4 <200 cells/mL.
In sub-Saharan Africa, KS remains the most frequent cancer among men, the third most frequent cancer among women, and the most common HIV-associated malignancy.

HHV-8 can be transmitted through blood transfusions, solid-organ transplants, and possibly through saliva.
HHV-8 is necessary, but not sufficient, to induce KS.
HHV-8 activates signaling pathways that promote an angiogenic-inflammatory state, leading to vascular proliferation that is the hallmark of KS.
HIV infection may promote KS progression by inducing cytokines and impairing host immunity.
Certain HIV gene products may play a role in tumorigenesis in KS.

Genetics
Genetic predisposition is suggested by the occurrence of classic KS in men of Mediterranean or Eastern European Ashkenazi descent.

HIV infection
Living in endemic areas (e.g., Zimbabwe, Uganda)
Immunosuppression (e.g., immunosuppressant medications, transplantation, chemotherapy)
High-risk sexual practices
Maternal–child transmission
Injection drug use
Exposure to infectious saliva
Contact with KS skin lesions
Blood transfusions and solid-organ transplants
HHV-8 viremia (associated with 9-fold increased risk of developing KS)
High antibody titers to HHV-8 related to faster development of KS and possibly to higher maternal–child transmission

Safe sex practices, avoid needle sharing, and careful screening of transplant organs; no anti–HHV-8 therapy is currently recommended for prevention.

HIV infection/AIDS; lymphoma

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