Clustering and aggregation of exposures in Hodgkin's disease.

The epidemiologic evidence regarding case clustering and aggregation of etiologic exposures among patients with Hodgkin's disease (HD) is reviewed. In contrast to the literature on leukemia, there are few reported HD clusters. Statistical studies searching for time-space clustering in HD have been negative or inconclusive. The innovative Long Island school study of Vianna and Polan suggests that there is aggregation of etiologic exposures in HD. However, this study has been criticized and further confirmation is required. Additional support for the aggregation of exposures hypothesis is found in studies of familial aggregation of HD. On the other hand, teachers and physicians, groups suggested as having high exposure to HD patients, have been shown to be at no increased risk for HD. Available evidence would suggest that if HD is communicable, it is probably so only prior to manifestation of the disease and exposure must occur in childhood or adolescence. Although most studies have focused on the compatibility of their findings with interpersonal transmission of an etiologic agent, these data are equally compatible with an hypothesis of common source exposure to non-infectious etiologic agents.