The epidemiology of classic, African, and immunosuppressed Kaposi's sarcoma

Abstract

The etiology of Kaposi's sarcoma remains somewhat obscure. While lesions of classic Kaposi's sarcoma, African Kaposi's sarcoma, and immunosuppressed Kaposi's sarcoma have been found to be indistinguishable from one another, the reasons for the variations in type and severity have not been established. The origin of the spindle cell is yet to be agreed on. Geographic variation does not seem as important as ethnic variation. The very young and the very old, perhaps two ages of weakened immunity, tend to have a higher incidence of Kaposi's sarcoma. Children and AIDS patients tend to develop more virulent disease. Males tend to get Kaposi's sarcoma at higher rates than do females. Jewish and Mediterranean males have the highest incidence of classic Kaposi's sarcoma, and African Bantu have the highest incidence of African Kaposi's sarcoma, classifications which do not apply to the Kaposi's sarcoma population in the United States. Male homosexuals have much higher incidence of Kaposi's sarcoma than do male heterosexuals, but since the early 1980s, its incidence as the presenting manifestation of AIDS has decreased dramatically. There is no unequivocal association with HLA haplotype (though DR5 carriers may be at especially high risk) or evidence of family clustering. There is an impressive but not always consistent association between Kaposi's sarcoma development and immunodeficiency. Environmental factors, such as nitrite use, immunosuppression, and repeated cytomegalovirus infection, are associated with Kaposi's sarcoma, but the exact mechanism is unclear and the associations remain inconsistent. Finally, it is still unclear if there is a causative infectious agent for Kaposi's sarcoma. While cytomegalovirus has been linked to Kaposi's sarcoma, there are weaknesses in its hypothetical role as an etiologic agent as is the case for HIV itself.(ABSTRACT TRUNCATED AT 400 WORDS)

PIP: The epidemiology of the 3 types of Kaposi's sarcoma, the endothelial tumor that occurs in classic, African, and immunosuppressed forms, associated pathological factors, potential causative agents, and a tentative model to explain the condition are contained in this review. Kaposi's sarcoma as classically described usually occurs in the lower limbs of elderly men, often from Mediterranean heritage, and progresses slowly. African Kaposi's sarcoma attacks the lymphatic system and viscera of all ages with a short survival time. Immunosuppressed people, especially AIDS sufferers, get a rapidly progressive but treatable form, that will regress if the immunosuppressive drug is withdrawn. Kaposi's sarcoma preceded the AIDS epidemic in the U.S., and it is apparently waning in AIDS patients. Factors linked to Kaposi's sarcoma include male gender, the HLA-DR5 genetic marker, abuse of nitrite drugs, exposure to semen or anal sex, or to several viruses. Cytomegalovirus is the most prominent of many viruses considered as a potential causal agent. Since many patients are free of CMV, it is now thought to be only a circumstantial factor because it is epidemic in Africa, is transmitted sexually, and causes immunosuppression. Several hypothetical models have been proposed to explain the phenomenon of Kaposi's, notably the multiple cofactor model, and the avian hemangiotosis retrovirus model, for an undiscovered sexually/enterically transmitted virus. It is possible that a single yet unknown agent, probably an oncogenic virus, with several routes of transmission, varying individual susceptibility, increased virulence for immune suppressed hosts, long latent period, and increasing endemicity is the infectious agent for Kaposi's sarcoma.