Tuberculosis

TUBERCULOSIS. - An infectious disease with a mostly chronic course, but sometimes tumultuous and fulminant, produced by a particular bacillus (Mycobacterium tuberculosis) identified by R. Koch in 1882.

The disease has an almost ubiquitous distribution and affects all ages, so much so that it is considered that, excluding infants, 40-50% of cadavers show lesions from t. as a cause of manifest or latent disease. Clinically the disease is more frequent between the 2nd and 7th year of life, but mortality reaches its peak between the 14th and 30th year.

All ages can however be affected, even old age, with lesions involving the most varied organs and systems, although by far more frequent than the others is the localization in the lungs (70% in adults). The enormous diffusion of t. is also attested by some recent anatomopathological statistics of Naegeli (Zurich) according to which lesions from t. are found in a percentage of 15% in the first decade of life, of 30-60% in the second decade and indeed of 99% in the last decades of life. According to Hamburger and Monti (Vienna), moreover, the tuberculin skin test (an index of a manifest or latent tubercular infection, active or already overcome), would be positive in a percentage of 99% of subjects, already from the 14th year of life.

The Koch bacillus, shaped like a slightly curved rod, is characterized by a particular resistance to acids and to common antiseptics, by virtue of a waxy enveloping capsule with which it is provided. This same capsule is probably also responsible for the scarce efficacy of the various therapeutic means known today and for the long survival of the germ in the external environment. Today three different types of t. bacilli have been identified: the human, the bovine and the avian, but only the first two appear to have importance in human pathology. These germs, having penetrated the organism, mostly through the respiratory tract (96% of cases), or also through ingestion (1.4% of cases, mostly infants breastfed with milk of tuberculous cows) determine characteristic alterations of the tissues, with the formation of so-called "tubercles" or "tubercular granulomas", which constantly evolve toward a particular type of tissue necrosis, "caseous necrosis". Consequently, depending on the virulence of the germ and the reactive capacity of the organism, there may be a relatively benign evolution, with fibrous transformation and calcification of the tubercular process (productive forms), or, on the contrary, a colliquation of the preformed caseous substance may intervene with ulceration and destruction of the host's tissues and formation of cavities and ulcers (exudative and caseous forms). Naturally there is not always such a rigorous schematism, so that in clinical practice there may be a simultaneous presence or an alternation of the two processes, so that Micheli more correctly speaks of "predominantly productive forms" and "predominantly exudative forms".

T. was for a long time considered a hereditary and familial disease, but at present ideas have notably changed. Hereditary t., in fact, that is, linked to the "genes" (preformed elements carrying hereditary characters, contained in the spermatozoon and in the ovum) and transmissible according to Mendelian laws, is today excluded by all authors. In very rare cases one can speak of congenital t., since this can be admitted only by demonstrating an ultraviral phase of the Koch bacillus, capable in this way of crossing the placental filter from mother to fetus, something moreover not demonstrated. The only possible cases, therefore, are those determined by the passage of the germ through possible placental lesions, during the course of pregnancy; thus today the general rule holds: one is not born tuberculous but becomes so. There exists, however, without doubt a particular hereditary predisposition to fall ill with t., demonstrated by statistics which affirm that children are tuberculous in 43% of cases if both parents are ill, in 33.15% if only one is ill, in 24.6% in the case of healthy parents. More therefore than of true heredity of the disease, one must speak of hereditary predisposition, linked to the particular constitution that the individual presents at birth and that makes him more subject to succumbing before the tubercular infection. It has in fact been seen that two particular biotypes (v.) are those that furnish the greatest number of patients: the longilineal asthenic biotype (Hippocratic phthisic habitus, Stiller's asthenic habitus), and the lymphatic biotype with exudative diathesis (Czerny's pasty habitus). While the first, however, due to the scarce reactivity of its tissues, easily succumbs before the germ, presenting the most serious forms with ulcerative and necrotizing evolution, the lymphatic biotype, endowed with a hyperactive defensive connective tissue, presents mostly chronic, circumscribed forms, with fibrous evolution and therefore relatively benign. Alongside however a predisposition to t., one must note the coexistence of a relative immunity toward the disease, testified by the fact that populations previously immune from tubercular infection, once they came into contact with the Koch bacillus, showed a mortality much higher than that of populations where t. is considered an endemic disease. The case of the inhabitants of the island of Tahiti suffices in this regard, who, having accidentally come into contact with the Koch bacillus, through Portuguese colonization, suffered in a short time a mortality from t. of 87.5%, the population being reduced from 80,000 to 7,000 individuals.

Contrasting facts, therefore, which are explained today with the modern theories of allergy and immunity (v. MICROBIOLOGIA), so much so that in the field of t. one speaks precisely of a "tubercular allergy", in the sense of a reaction deviated from the normal. Ranke, who has greatly occupied himself with the problem, distinguishes three phases of the allergic process of the organism that has come into contact with the bacillus of t. A first stage characterized by intense reaction of the affected tissue and formation of the "primary complex"; a second with a tendency toward generalization of the process due to hypersensitivity of the tissues to the harmful action of the germ; a third stage, finally, characterized by a relative immunity and by the tendency of the lesions to localize in a single organ. This simplism and schematism is perhaps excessive and cannot fully clarify the complex allergic problem of t., yet it helps not a little to clarify the diversity of behavior, not only of single individuals, but of entire populations, before tubercular infection. Among European populations, in fact, it is much more frequent that from the earliest years of life the search for the existence of a tubercular infection proves positive, but, on the other hand, the continuous contact with the germ and with its toxins, brings it about that the benign productive forms due to the state of relative immunity prevail clinically.

From the clinical point of view, tuberculous disease can be distinguished into primary t. (characterized by the "primary complex," for the most part localized in the lung) and post-primary t., which, while it chiefly affects the lungs, can localize in any other organ or region (serous membranes, nervous system, peritoneal organs, bones, urogenital apparatus, endocrine glands). The course of the various localizations is for the most part chronic; but sometimes the t. takes on a tumultuous and rapidly fatal course, whether with regard to the extent of the process (miliary forms), or to its severity in itself (galloping phthisis or confluent caseous bronchopneumonia), or to the importance of the organ involved (tuberculous meningitis, t. of the adrenals), or in relation to the particular conditions of the subject's energy (t. of infants, of alcoholics). At other times the t. can run its course entirely without symptoms and pass unnoticed by the individual, but such insidious forms are nevertheless of great importance from the medical and social point of view, constituting a continuous source of contagion for the community. The t. is in fact of the greatest importance from the social point of view, both because of the damage it produces to the eugenics and the demographic movement of a nation (some authors attribute to tuberculous intoxication of the fetus the capacity to determine even states of psychodegeneration), and because of the harm it can bring from the economic point of view owing to its characteristic chronicity, and also because of the contagiousness and the high mortality already mentioned above.

The fight against t. is carried on first of all actively in a prophylactic sense. Such prevention is today implemented everywhere directly by the State, or at least under its control, according to two guidelines: strengthening the organism so as to increase its capacities of resistance to infection, particularly during the age of development (establishment of colonies for predisposed persons, supplementary rations, vaccinations, various hygienic rules); reducing to the minimum possible the probability of contagion by means of the isolation of the sick (sanatoria, villages built expressly for the purpose such as those of Papworth in England and Claire-vivre in France) and the disinfection of environments.

Besides in the prophylactic field, notable progress has been achieved in these last decades in the therapeutic field. Current therapy aims principally at three goals: increasing the organism's defensive powers, combating Koch's bacillus, circumscribing and reducing in every way, even surgically, the lesions already caused, so as to avoid the spread of the disease and bring about the formation of a permanent scar. Important, therefore, have been the discoveries of certain drugs endowed with bacteriostatic and bactericidal power against Koch's bacillus such as "soifone," "streptomycin," "para-aminosalicylic acid" and "isonicotinic acid hydrazide," which have made it possible to modify favorably the prognosis of certain tuberculous forms once considered to have a constantly ill-fated outcome, such as miliary t. and tuberculous meningitis. Results not equally satisfactory have been obtained with the aforesaid drugs in pulmonary cavitary forms, in which every chemotherapeutic therapy must be associated with collapse therapy. This therapy, initiated by Forlanini, is based essentially on the principle of putting the part of the diseased lung at rest so as to permit easy scarring of the tuberculous lesion. An essential method is therefore pneumothorax (pnx), with which air is introduced into the pleural cavity in a quantity such as to neutralize the negative pressure normally existing in the pleural cavity. Over time this method has been increasingly perfected and has also undergone modifications, so that today not only is a hypertensive pnx distinguished from a hypotensive one, a homolateral one from a contralateral one and a bilateral one, but an extrapleural pnx is also performed when the presence of excessive adhesions between the parietal pleura and the visceral pleura prevents the introduction of air into the pleural cavity. There exist moreover today numerous other methods of collapse therapy of a purely surgical nature, but not devoid of beneficial effect in determined circumstances (pleuritis, intrapleural, phrenicectomy, partial or total ablation of the diseased lung, etc.). According to the majority of modern authors, tuberculous therapy must always be founded, in pulmonary forms, on collapse therapy, but one cannot deny the beneficial effect of antitubercular drugs, especially from the social side, given the capacity they have to render tuberculotics no longer contagious, who, as is known, transmit the disease in the environment by means of the microscopic droplets of saliva projected with the cough and containing Koch's bacilli.

A final mention must be made of the medico-moral problems connected with t. They concern particularly: the internment of the sick, the imposition of a determination as to the presence or absence of the disease, marriage and pregnancy. In all these cases the inevitable clash is evident that a coercive legislation, which places the interest of the community in the first place, can have with regard to the rights of the human person. Finally, it must be remembered that, until a few years ago, t. constituted one of the most frequent indications for performing therapeutic abortion (v.). At present, however, the majority of physiologists and gynecologists hold that, although on the one hand, in certain grave forms, it is advisable to avoid pregnancy, on the other hand therapeutic abortion is to be proscribed because of the grave harm that the interruption of pregnancy inevitably brings with it; all the more so since in the graver forms spontaneous abortion readily occurs, less traumatizing and dangerous than the induced one.

Alessandro Marolla