The other and essential characteristic of tuberculous disease is the infectious granuloma to which it gives rise. This is a term first applied by Virchow to new formations of granulation tissue which are the result of the presence of invading and specific irritants. This tissue varies little in type from that already described under Ulcers, and is common to the neoplasms which are found in tuberculosis, syphilis, leprosy, glanders, and other local infections. So little does the tissue type vary in these different instances that it is difficult to distinguish by microscopic sections of the unstained tissues, or at least those unstained for bacteria, to which class of lesions they belong.
PLATE VII
Lupus of Skin. (Gaylord.)
a, fresh tubercles containing numerous plasma cells; b, mature tubercle with giant cells. Below are accumulations of plasma cells about the vessels. Low power.
Unna’s polychrome methylene blue.
This tissue may be met with in any of the tissues of the body, but is less seen upon the serous membranes of the cranial and peritoneal cavities, whereas in the joint cavities it is common. It is provoked, as just stated, by the presence of tubercle, and has the power of penetration into and substitution for almost all the other tissues of the body. Thus in a primary tuberculous focus within the bone a granuloma will form and extend its limits, while the surrounding bony tissue melts away before it; and it is by the growth of this tissue in a particular direction that tuberculous products from within the bone cavity are finally carried to the surface. When this material has escaped from bone, or from tissues without the bone, toward the surface its presence is marked by induration, by livid discoloration of a limited area of skin, with elevation of the surface, which finally breaks down and shows discolored, bleeding, and pouting granulations, which in the absence of restraint now proliferate more rapidly, and often to the point where they loose their former blood supply, and consequently necrose upon the surface. This is the fungous granulation tissue, especially of the German writers, and may be met with upon the surface, or is frequently seen in opening into joint cavities and other tissues infected by tubercle. The appearances of this fungous tissue are modified somewhat by environment and pressure: in joints flat and radiating masses of it will be found, extending along the synovial surfaces and into the articular crevices. This fungous tissue may grow in any direction, but apparently advances in the direction of least resistance. It leads to complete perforations of the flat bones, like those of the skull, while tuberculous masses from the dura may cause multiple perforations, the granulation tissue finally escaping through the overlying skin. In tuberculosis of synovial sheaths and bursæ it extends along and may completely fill and even distend them. It will separate tissues which were united together, and it may lead to disintegration and disorganization of the firmest textures in the body. So long as it is not exposed to the air nor to pyogenic infection, it will preserve its characteristics for a considerable length of time. Immediately upon exposure it is likely to break down, and infection will travel speedily along it into the deeper cavity whence it has sprung. A mass of this tissue contained within the normal tissues, condensed more or less by pressure, uninfected, and not freely supplied with blood, is entitled to the name of tuberculous gumma, whose tendency, however, is too often to break down and suppurate. Such gummas may be found in any part of the body, and differ only in unessential respects from the diffuse and more or less infiltrated masses of granulation tissue which occupy serous cavities or which extend in various directions.
The lesions of surgical tuberculosis, except those already spoken of as constituting cold abscess, are so essentially connected with the presence of granulation tissue, just described, or of this form of the infectious granulomas, that no student can appreciate the subject until he is familiar with this tissue in its various phases and in various locations. Of such great importance is it that this be realized that some of the local manifestations of this new tissue must here be considered, although they may be rehearsed in other form in succeeding chapters.
In the skin and subcutaneous tissues and in and under mucous membranes this granulation tissue may be studied at places where it is free from most mechanical restraints to growth, and where, in other respects, its appearances are typical. The most characteristic manifestations in the skin occur as lupus, a disease considered cancerous or of uncertain etiology. Lupus is always a cutaneous manifestation of this protean disease. (See [Plate VII].)
In its incipient stages lupus consists of multiple minute nodules of granulation tissue just beneath the surface, containing all the elements of true miliary tubercle, with infiltration of the surrounding skin, even into the subcutaneous fat. The most common location of these lesions is on exposed surfaces. Bacilli are not numerous in them, yet may be demonstrated. The tendency is more or less rapidly to break down, the result being a tuberculous ulcer, which, as it extends, manifests usually a disposition to cicatrize in the centre while enlarging around its periphery. The dermatologists describe several different forms of lupus under the names hypertrophicus, vulgaris, maculosus, etc., all of which are essentially the same in character, the differences being largely constituted by the rapidity or slowness with which the granuloma of the skin breaks down. From the surface these growths may extend and involve parts at considerable depth, even the periosteum. This name should also include the lesions described as scrofuloderma or scrofulous ulcers of the skin, they being all of the same character.
A variety known as anatomical tubercle has been described by some writers, found especially upon the hands of those who frequent dissecting-rooms or handle dead bodies, and is supposed to be the result of local inoculation. It appears usually as a warty growth, which ulcerates and becomes covered with a scab—is usually indolent in character, but is followed by lymphatic involvement, and in rare instances by death from tuberculous disease.