Antagonism Among Diseases

Keil came to the conclusion that the relative cellular and tissue reactivities of lepromatous and tuberculoid leprosy patients were such as to make the spread of carcinoma, in the advent of cancer invasion, much more likely in the former than the latter type. An aCtual review of the findin gs of some 17 authors appeared to Keil to substantiate this theoretic concept. His review of their studies brought out the fact that carcinomatous development was twice as frequent in lepromatous as in tuberculoid cases . In the current issue of THE JOUHNAL at least three items bear' on the relations and possible mutual exclusiveness of carcinoma and leprosy. Two original articles illustrate a common findin g, viz., that early reports of an antagonism or mutual exclusiveness do not hold up in the light of thorough, conb'olled study. Michalany ( 'j ) noted that up to about twenty years ago the impression prevailed that leprosy and cancer were rarely associated in the same patient. Many records in the literature seemed to sustain this opinion. Studies in 1937 by two Brazilian authors (G) however, made on a larger series of 318 I ntemational J oumal of Lepmsy 1966 cases than were considered in most of the studies in the past, indica ted that cancer was not rare in leprosy patients, and that there was no reason to believe in an incompatibility of the two diseases. Michalany's own studies, based on observation of 539 cases of malignant tumors of the skin in patients with leprosy, have strongly supported this view. In another original article in this issue of THE JounNAL Riedel has revised a previous concept of his own in this respect. Job and Riedel had stated that "Carcinoma arising out of p lantar ulcers seems to be extremely uncommon." Riedel's later studies have led him to the conclusion that malignancy in plantar ulceration in leprosy is not quite as rare as is generally believed, and that it may develop sooner than is likely to he expected . Such studies inevitably tend to our own conclusion th at more extended studies generally lead to revision of early notions based on inadequate data. So many biologic factors , including age and varying degrees of exposure to environmental influences, come into play, that large volumes of data and careful statistical evaluation are necessary to establish what we ultimately may accept as facts. But the very volume of past conflicting data overwhelms us. The association of cancer and tuberculosis has been a similar problem, with proponents for and against a mutually exclusive relation. Everybody knows that the two diseases may occur in the same body, but the frequency of such association in the light of statistical controls, taking account of varying environmental factors, and the fact that one disease, tuberculosis, is declining in prevalence, while the other, cancer, is rising, is still a subject of controversy. Finally a query has been made in this issue of THE JOURNAL (9) with regard to the association of malignant lymphomas and leprosy. Substantial information on the subject being as slender as it is, it will not be surprising if a long time is required to reach a satisfactory conclusion relative to the frequency of this association. The problem is complicated by the inadequacy of data on the etiology of the two diseases. Leprosy is presumptively of hacterial origin ; some, at least, of the lymphomas appear to be of viral etiology. The field of virus research is expanding so rapidl y that clements that may be of importance develop frequently and unexpectedly. For example, the discovery of "interferons" b y Isaacs and Lindenman (3) in the laboratories of the National Institute for Medical Research in London, now accepted and well studied as elements concerned in resistance to and recovery from virus infections , may be pertinent in conncction with the problems of viral tumors. Studies on these unique substances have shown that the products of damage to a cell by one virus may have an inhibiting effect on the proliferation of another virus. It is too early to say, but it is fair to state now that the problem is highl y complex, and far from easily solved. In general, studies in the field of antagonism between leprosy and other diseases, are much too fragmentary to settle most of the major ques tions at issue. Rut there is little doubt that adequate investigation with proper statistical control of all variables presently recognized, would be rewarding for understanding of the natural history of leprosy. -E. R. LONG