Pathophysiology and epidemiology of epidemic Kaposi's sarcoma.

The epidemic form of Kaposi's sarcoma (KS) that occurs in patients with the acquired immune deficiency syndrome (AIDS) produces lesions that, histopathologically, are indistinguishable from those of classical KS or of the endemic form of the disease seen in children and adults in certain areas of Africa. There are, however, important differences in the pathogenesis of the disease in the different groups affected by the neoplasm. Compared with classical KS in people of eastern European and Mediterranean descent, which commonly takes a protracted, indolent course, the epidemic Kaposi's sarcoma (EKS) is far more aggressive. However, the KS seen in adults in endemic areas of Africa may also become florid and rapidly progressive after years of quiescence. Some degree of immune dysfunction is thought to be a factor in all forms of KS, with immune depression being the hallmark of EKS and the setting in which it occurs. Cytomegalovirus (CMV) is thought to be at least a cofactor in the disease, but it has also been suggested that the etiologic agent of AIDS, human immunodeficiency virus (HIV), may also play a role in EKS.