Mucoid Degeneration

MUCOID DEGENERATION, one of the types of protein degeneration, morphologically characterized by the appearance of true mucus in tissues (see Mucus). The mechanism of mucus appearance in connective and in adult epithelial tissues differs substantially. The conditions under which mucoid degeneration of connective tissue and epithelium is observed also differ. The mechanism of mucus appearance in epithelial cells during mucoid degeneration apparently does not differ from ordinary secretion, for which reason the application of the term mucoid degeneration to epithelial tissue is questioned. Nothing is also known about the change in quality of the mucus itself, but quantitatively, the secretion of mucus in epithelium is expressed significantly more, mucus is produced not only in differentiated, goblet-type cells of cylindrical epithelium, but generally throughout the entire epithelial covering, and not only of cylindrical type, but also in multi-layered flat, for example, in the conjunctiva. Moreover, the further fate of secreting cells is different-they die quickly in significantly larger quantities than normal, especially in mucous cancers. Also, the circumstances under which the above-mentioned increased secretion of mucus occurs-chronic irritation, inflammatory process, epithelial tumors-all this allows one to continue applying the term mucoid degeneration to epithelial tissue, albeit with certain reservations. The matter is different with the formation of mucus in all varieties of connective tissue. The presence of mucus in adult connective tissue is always pathology. Morphologically this is expressed in the gradual disappearance of intercellular substances (bone, cartilage, collagen fibers); these substances swell, as if dissolving in the mucus that replaces them. The shape of the cells themselves also changes, most often they acquire the appearance of star-shaped cells with long anastomosing processes, sometimes triangular or spindle-shaped elements are found. With diffuse mucoid degeneration of tissues, one can speak of their myxomatosis. Mucoid degeneration can be diagnosed with complete certainty only by using appropriate reactions, since macroscopically identical pictures will also occur with the appearance of pseudomucin. And even the picture of serous atrophy of adipose tissue or prolonged tissue edema can macroscopically and microscopically simulate true mucoid degeneration. The mechanism of mucus formation in connective tissue is not precisely clarified. Does mucus arise from the interstitial substance without the participation of cell chondriosomes, i.e., according to the type of actual tissue degeneration, or is there still participation of connective tissue cell forms in the formation of mucus-the question is open. In the literature there is an opinion that connective tissue cells produce mucus and that mucus is a derivative of their perinuclear protoplasm, as in epithelium. In recent times, however, the opinion has been expressed that the appearance of mucus in connective tissue is a kind of mucoid decomposition-the revelation of former embryonic visible mucous substances. The occurrence of mucus in the stroma of colloid cancers is explained more simply-in them, apparently, a simple infiltration of connective tissue with mucus produced by epithelium is observed. The formation of mucus in various myxomas can be interpreted such that these tumors developed from embryonic tissue that retained mucus (see Myxoma). For example, the presence of mucus in joint ganglia is explained precisely by the fact that these ganglia are formed from detached embryonic rudiments. Mucoid degeneration of connective tissue is usually observed in chronic exhausting diseases. Under similar conditions, pictures simulating mucoid degeneration can also be observed-namely, edema, serous atrophy of adipose tissue, the appearance of pseudomucin, which emphasizes the need for differentiation of mucoid degeneration by microchemical methods.