Kaposi Sarcoma

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Basics

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

Description

  • 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.

Epidemiology

  • 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.

Etiology and Pathophysiology

  • 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.

Risk Factors

  • 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

General Prevention

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

Commonly Associated Conditions

HIV infection/AIDS; lymphoma

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