Localization of Diseases

LOCALIZATION OF DISEASES (Latin sedes morbi), the site of the development of pathological processes. Such a site can be any section of any tissue or organ. This general theoretical proposition, constantly confirmed by the practice of the clinician and pathologist, nevertheless requires a correction, consisting in the fact that some organs, and sometimes even parts of the latter, become diseased less often than others. The diversity in the localization of diseases makes understandable the significant diversity in the symptomatology of the afflictions known to us: diphtheria, for example, can anatomically be localized in the pharynx, nose, larynx, or skin; typhoid fever can be ileotyphus or colotyphus; rheumatism can affect the cardiovascular system, can manifest as polyserositis, chorea, etc. Despite this, every disease has a certain typical localization of pathological processes. Knowledge of typical localization is an elementary condition for recognizing specific disease forms, and the totality of mechanisms leading to such a localization of an affliction is designated as its pathogenesis. The localization of diseases can be precisely definable in spatial terms, e.g., a fracture of the femur, a fibromyoma of the uterus, cancer of the stomach. All so-called organopathology can serve as an example of such organ localization of diseases. Along with organ localization, there can be systemic localization, when one or another pathological process encompasses simultaneously or sequentially homogeneous tissues or a system of organs united by a commonality of morphological and physiological characteristics. Such, for example, is the localization of diseases in leukemia or lymphosarcomatosis. To such systemic localizations one can attribute bone carcinosis, nephritis, hepatolienal diseases, etc. Sometimes, however, one and the same factor can cause disease of two or more organs that are not physiologically connected to each other (see Pleiotropy); for example, the involvement of the liver, spleen, and brain in Wilson's disease (see). It should be borne in mind that the identity sometimes observed in the localization of diseases in two specific cases, even with morphological identity, by no means speaks to the identity of the mechanisms in the development of these localizations. One of them may, for example, turn out to be genotypic, the other paratypic, and in genotypic cases, the difference in pathogenesis (with similar localization and clinical picture) may be conditioned by a difference in genes (different chromosomes or different points of the same chromosome) underlying the disease. The mechanisms of disease development can be extremely complex; in particular, their center of gravity can be located far beyond the limits of the organ or system where the disease is currently localized. Such are many skin afflictions, for example, on an endocrinological or neuropathological basis; the connection of certain diseases of the endometrium (metropathies) and ovulation processes, etc. The concept of the localization of diseases in a pathogenetic sense by no means coincides, therefore, with the concept of something local, completely isolated; the local is often a factor producing the general, and, conversely, the local often turns out to be a derivative of the general. From what has been said, one can