PREDISPOSITION

PREDISPOSITION, a term used in pathology to denote a tendency of the organism to a particular disease. From ancient times, it has been customary to divide the etiological moments of diseases into predisposing and producing causes, with the former being understood as factors that merely create favorable conditions for the disease, while the latter are what, in the presence of a predisposing factor, serve as the immediate cause (sometimes merely a trigger) of the disease. But although the difference between these two might seem sufficiently clear, different authors do not quite invest the concept of 'predisposition' with the same meaning. According to one definition, P. in the narrower sense of this word is a tendency to disease based on special properties of the organism, i.e., a strictly endogenous moment in the origin of the disease; according to another, broader definition, P. 'represents generally everything that has some connection with the disease, regardless of whether it is of endogenous or exogenous character; consequently, to express it briefly, the probability of disease' (Siemens). Some authors (Baumgarten) differentiate between the concepts denoted by the German words Anlage and Disposition, namely, while the latter denotes a state from which disease arises only with the assistance of a second factor necessary for its development, the former characterizes a state that in itself is sufficient for the development of disease under ordinary conditions, without the participation of the aforementioned second factor. Gout, for example, often manifests itself in members of families predisposed to this disease who lead a perfectly correct, simple way of life, carefully avoiding everything that is considered relevant in this regard. The same is true of diseases such as alkaptonuria, Friedreich's disease, Tay-Sachs disease, etc. Conversely, tuberculosis is caused by a specific infectious agent, but not everyone contracts it despite the extreme prevalence of the pathogenic agent. In this case, we are therefore justified in speaking of P., which is either inherited under certain conditions or acquired during individual life. In private pathology, P. to a particular disease is usually spoken of only when there is a special, increased susceptibility to this disease compared to most individuals of this species. The relationship between P. and producing causes varies in different cases, depending on the degree of pathogenicity of the latter: when the pathogenic power of disease-causing factors is great, the role of P. drops to zero, and practically it need not be considered in such cases (compare, for example, the action of sulfuric acid in sufficient concentration on tissues); in other cases, such as most infectious diseases, P. plays a very essential role: numerous cases of so-called bacillus carriage while maintaining health in carriers of the infectious agent can serve as an illustration of this. The essence of P. cannot always be clarified, but it is quite obvious that the problem of P. is above all a problem of pathogenesis; P. denotes a certain readiness of pathogenetic mechanisms, i.e., a certain anatomical-physiological conditioning of the disease. Therefore, when relating P. to etiological factors, it is necessary to make the qualification that not P. as such is the etiology of the suffering, but those factors (genotypic, phenotypic, etc.) that create this P. It is also obvious that in those cases where P. is simultaneously a producing factor, i.e., when for the development of the disease even purely physiological moments are sufficient (for example, in menstrual, puerperal psychoses, in the mentioned cases of gout, etc.), the pathogenetic essence of P. should be understood only as a specific feature of the constitution, of the entire psychic and somatic structure of the personality, and the unfolding of pathological phenomena should be considered in unity with the unfolding of the entire psychophysiological life of the subject: pathological and physiological here represent a single whole. Types of P. One can first of all distinguish between idiotypic, or genotypic P., and paratypic, or P. acquired during individual life under the influence of various conditions. As for the possibility and difference of these two types of P. in each specific case, the same must be said as for idiotypic and paratypic diseases, namely, that here one encounters both relatively pure cases of each kind and a whole scale of intermediate forms, in which genotypic and paratypic factors appear to varying degrees. The differentiation between these two practically acquires great importance from the point of view of prognosis and therapy. The existence of genotypic P. is also proven experimentally - susceptibility to rust and cold resistance in barley and cold sensitivity in Mirabilis jalapa turned out to be Mendelian, dependent on specific hereditary factors. The existence of paratypic, acquired P. is also beyond doubt: the well-known fact of the appearance of a disposition to pyogenic skin diseases as a result of diabetes can serve as an example, and cases of immunity acquired as a result of having had an infection or preventive vaccinations demonstrate paratypic fluctuations in P. in the opposite direction. It goes without saying that genotypic predisposition can undergo changes and fluctuations under the influence of the environment, which has a decisive effect - favorable living conditions can weaken and even paralyze it, unfavorable ones can strengthen it. This explains why even in monozygotic twins some differences in P. to certain diseases are observed. One can also speak of species, racial, constitutional, sexual, age, professional, and social P. An example of species P. can be the greater sensitivity of guinea pigs to M. tuberculosis typi humani and, conversely, the slight sensitivity to human tuberculosis of cattle, which is however very susceptible to M. tuberculosis typi bovini, or the wide distribution of tumors in fish⁴ (see Tumors - distribution of tumors in the animal world); the turtle is not sensitive to tetanus toxin, rabbits are little sensitive to atropine, the gonococcus is pathogenic only for humans and monkeys, etc. The high mortality from tuberculosis among colored races upon moving to Europe (French colored troops during the world war) is known, which was explained by the absence in them of even relative immunity to this disease, although undoubtedly other factors also play a role here (change of climate, other living conditions). The particular malignancy of tuberculosis among Kalmyks, noted by Metchnikoff and Tarasevich, is explained not only by racial peculiarities but to no lesser degree also by living conditions. In general, to isolate the racial factor in morbidity is extremely difficult both in essence and because in European and American statistics morbidity by races is not recorded, while morbidity in different climates is not comparable to each other. An obvious example of racial P. can be the fact of the different attitude of white and gray rats to anthrax. The term 'predisposition' is also used to denote species susceptibility to diseases, but in this case a different content is invested in the concept of P., since here we are dealing with phenomena of a different order. On the one hand, in a number of cases it is indeed possible to compare different degrees of susceptibility of species (or their resistance) to, for example, different infections. Thus, man is more resistant to anthrax than cattle, guinea pigs are more predisposed to tuberculosis than other laboratory animals, tumors occur more frequently in fish than in other cold-blooded animals, etc. On the other hand, here we are dealing with the fact of special species diseases that occur in one and do not occur in other species, for example, of all vertebrates only humans and anthropoid apes contract syphilis, while other vertebrates are not susceptible to syphilis. Strangles affects only horses, but no other domestic animals nor humans ever contract it: In such cases, it is more correct not to use the term 'predisposition', since we are no longer talking about a susceptibility, the intensity of which can vary, but about a complete possibility or impossibility of contracting the disease. About constitutional P.-see Constitution. *z Different morbidity by sex is observed in relation to many diseases. In this case, P. can be caused by 1) biological peculiarities of one sex or the other (for example, mastitis in women, inguinal hernia in men) and 2) differences in living and professional conditions (for example, alcoholism and trauma in men). In the first case, sexual P. is constant and persistent, in the second it is temporary, as long as the differences in living conditions and professional peculiarities persist. From these cases, diseases linked to sex should be distinguished, where diseases are determined by a gene linked to sex, such as hemophilia (see), color blindness (see).

Here one cannot speak of P. as a predisposition to disease associated with biological peculiarities of sex; in these cases we have before us a fact of pathological individual peculiarities realized through a genetic mechanism, i.e., a hereditary disease. The significance of age in P. is enormous: it is sufficient to point to childhood infectious diseases. The causes of children's predisposition to different diseases are diverse and cannot always be fully clarified. Here both anatomical peculiarities (for example, non-fusion of fissurae petro-squamosae as a condition favorable to purulent meningitis) and peculiarities of metabolism in connection with growth play a role, due to which, for example, a deficiency of Ca in a child's food will have different consequences than for an adult, and again special conditions of the entire life situation. Old age in turn has its own special P., the mechanism of which in some cases is completely clear (fractures of bones), in others is not yet clarified (malignant tumors). As with diseases associated with sex, here we also often have before us a connection that lies not in the biological peculiarities of structure and function, but in other conditions. This includes above all all professional diseases, which are naturally connected with mature age and professional experience. The gradually increasing wear and tear of the body with age, the long duration of the action of harmful factors lead to the fact that certain diseases occur the more frequently the higher the age, for example, dental caries. Many diseases are directly connected with one or another profession. This includes not only diseases associated with professional hazards (for example, foundry fever, chimney sweep's cancer) but also such diseases as arise because the profession, overstraining one or another organ, creates a locus minoris resistentiae (for example, diseases of the vocal cords in singers). However, professional P. is not an inalienable attribute of the profession, since the progress of technology, improvement of hygienic working conditions, reduction of working time, etc. can completely eliminate not only professional diseases but also predisposition to them. From the examples given above it is clear that in its essence P. arises and is determined not by individual but by general living conditions. The history of epidemics gives many bright examples of the fact that not only individuals but entire classes and even peoples for social reasons became in a particularly threatened position. There is a whole series of diseases, the etiology of which seemingly lies outside the social sphere, but which are nevertheless most closely connected with social conditions and P. to which is obviously socially conditioned. This includes such diseases as tbc, venereal diseases, rickets, scurvy, etc. The presence of correlation of P. with social conditions is statistically proven and a priori obvious, since insufficiency of nutrition, bad housing conditions, excessive work, etc. undoubtedly cannot fail to have a weakening effect on the body and not be reflected in a decrease of its resistance to external harmful conditions, including infection. And since such harmful factors exist for a long time, they lead to a wide and more or less stable P. to disease by the most various diseases, especially for the exploited classes of society. By what path this social P. is realized in one or another case, in which particular disease it is realized, this can be individually different, depending on the place and time, as well as other age, sex, and other peculiarities of a given individual, but each concrete case nevertheless remains etiologically connected with the general social conditions. Lit.: Siemens G., Introduction to the pathology of human heredity. M.-L., 1927; Bauer J., Konstitutionelle Disposition zu inneren Krankheiten, B., 1924 (lit.); Baumgarten V., Die Lehre von den Krankheitsanlagen (Handbuch der allgemeinen Pathologie, herausgegeben von L. Krehl und F. Marchand, Band 1, Leipzig, 1908). See also literature for the article Constitution.